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Search for "glycol" in Full Text gives 277 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Benzylic C(sp3)–H fluorination
- Alexander P. Atkins,
- Alice C. Dean and
- Alastair J. J. Lennox
Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137
- achieved. Product 21 could be resubjected to the reaction conditions, affording difluoride 22 in 46% yield. Metal fluorides are an economical source of nucleophilic fluorine, but are sparingly soluble in organic solvents. To overcome this, in 2012, Fuchigami and co-workers used polyethylene glycol (PEG) to
Graphical Abstract
Figure 1: A) Benzylic fluorides in bioactive compounds, with B) the relative BDEs of different benzylic C–H b...
Figure 2: Base-mediated benzylic fluorination with Selectfluor.
Figure 3: Sonochemical base-mediated benzylic fluorination with Selectfluor.
Figure 4: Mono- and difluorination of nitrogen-containing heteroaromatic benzylic substrates.
Figure 5: Palladium-catalysed benzylic C–H fluorination with N-fluoro-2,4,6-trimethylpyridinium tetrafluorobo...
Figure 6: Palladium-catalysed, PIP-directed benzylic C(sp3)–H fluorination of α-amino acids and proposed mech...
Figure 7: Palladium-catalysed monodentate-directed benzylic C(sp3)–H fluorination of α-amino acids.
Figure 8: Palladium-catalysed bidentate-directed benzylic C(sp3)–H fluorination.
Figure 9: Palladium-catalysed benzylic fluorination using a transient directing group approach. Ratio refers ...
Figure 10: Outline for benzylic C(sp3)–H fluorination via radical intermediates.
Figure 11: Iron(II)-catalysed radical benzylic C(sp3)–H fluorination using Selectfluor.
Figure 12: Silver and amino acid-mediated benzylic fluorination.
Figure 13: Copper-catalysed radical benzylic C(sp3)–H fluorination using NFSI.
Figure 14: Copper-catalysed C(sp3)–H fluorination of benzylic substrates with electrochemical catalyst regener...
Figure 15: Iron-catalysed intramolecular fluorine-atom-transfer from N–F amides.
Figure 16: Vanadium-catalysed benzylic fluorination with Selectfluor.
Figure 17: NDHPI-catalysed radical benzylic C(sp3)–H fluorination with Selectfluor.
Figure 18: Potassium persulfate-mediated radical benzylic C(sp3)–H fluorination with Selectfluor.
Figure 19: Benzylic fluorination using triethylborane as a radical chain initiator.
Figure 20: Heterobenzylic C(sp3)–H radical fluorination with Selectfluor.
Figure 21: Benzylic fluorination of phenylacetic acids via a charge-transfer complex. NMR yields in parenthese...
Figure 22: Oxidative radical photochemical benzylic C(sp3)–H strategies.
Figure 23: 9-Fluorenone-catalysed photochemical radical benzylic fluorination with Selectfluor.
Figure 24: Xanthone-photocatalysed radical benzylic fluorination with Selectfluor II.
Figure 25: 1,2,4,5-Tetracyanobenzene-photocatalysed radical benzylic fluorination with Selectfluor.
Figure 26: Xanthone-catalysed benzylic fluorination in continuous flow.
Figure 27: Photochemical phenylalanine fluorination in peptides.
Figure 28: Decatungstate-photocatalyzed versus AIBN-initiated selective benzylic fluorination.
Figure 29: Benzylic fluorination using organic dye Acr+-Mes and Selectfluor.
Figure 30: Palladium-catalysed benzylic C(sp3)–H fluorination with nucleophilic fluoride.
Figure 31: Manganese-catalysed benzylic C(sp3)–H fluorination with AgF and Et3N·3HF and proposed mechanism. 19...
Figure 32: Iridium-catalysed photocatalytic benzylic C(sp3)–H fluorination with nucleophilic fluoride and N-ac...
Figure 33: Iridium-catalysed photocatalytic benzylic C(sp3)–H fluorination with TBPB HAT reagent.
Figure 34: Silver-catalysed, amide-promoted benzylic fluorination via a radical-polar crossover pathway.
Figure 35: General mechanism for oxidative electrochemical benzylic C(sp3)–H fluorination.
Figure 36: Electrochemical benzylic C(sp3)–H fluorination with HF·amine reagents.
Figure 37: Electrochemical benzylic C(sp3)–H fluorination with 1-ethyl-3-methylimidazolium trifluoromethanesul...
Figure 38: Electrochemical benzylic C(sp3)–H fluorination of phenylacetic acid esters with HF·amine reagents.
Figure 39: Electrochemical benzylic C(sp3)–H fluorination of triphenylmethane with PEG and CsF.
Figure 40: Electrochemical benzylic C(sp3)–H fluorination with caesium fluoride and fluorinated alcohol HFIP.
Figure 41: Electrochemical secondary and tertiary benzylic C(sp3)–H fluorination. GF = graphite felt. DCE = 1,...
Figure 42: Electrochemical primary benzylic C(sp3)–H fluorination of electron-poor toluene derivatives. Ring f...
Figure 43: Electrochemical primary benzylic C(sp3)–H fluorination utilizing pulsed current electrolysis.
Synthetic applications of the Cannizzaro reaction
- Bhaskar Chatterjee,
- Dhananjoy Mondal and
- Smritilekha Bera
Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120
- reaction of tetraethylene glycol (TEG) was accomplished by Vida et al. [29] using a barium compound. Different types of solvents were also applied for the Cannizzaro reactions. The use of aqueous or solvent-free conditions has played pivotal roles in terms of environmental consciousness and a greener
- Cannizzaro reaction of dialdehyde 23, synthesized from tetraethylene glycol (TEG) 22. The dialdehyde 23 underwent a clean desymmetrization to form the hydroxy carboxylic acid derivative 24. The reaction was mediated by Ba2+ which perfectly bound the TEG and allowed the aldehyde functionalities to be placed
- ethylene glycol units of different chain lengths ranging from 2–5 (25, 26, and 27), by varying the aromatic substitution in the ortho, meta and para-positions and finally obtained the desymmetrized products 28, 29, and 30 in good to excellent yields (Scheme 15). This has been effectively depicted in the
Graphical Abstract
Figure 1: Types and mechanism of the Cannizzaro reaction.
Figure 2: Various approaches of the Cannizzaro reaction.
Figure 3: Representative molecules synthesized via the Cannizzaro reaction.
Scheme 1: Intramolecular Cannizzaro reaction of aryl glyoxal hydrates using TOX catalysts.
Scheme 2: Intramolecular Cannizzaro reaction of aryl methyl ketones using ytterbium triflate/selenium dioxide....
Scheme 3: Intramolecular Cannizzaro reaction of aryl glyoxals using Cr(ClO4)3 as catalyst.
Scheme 4: Cu(II)-PhBox-catalyzed asymmetric Cannizzaro reaction.
Scheme 5: FeCl3-based chiral catalyst applied for the enantioselective intramolecular Cannizzaro reaction rep...
Scheme 6: Copper bis-oxazoline-catalysed intramolecular Cannizzaro reaction and proposed mechanism.
Scheme 7: Chiral Fe catalysts-mediated enantioselective Cannizzaro reaction.
Scheme 8: Ruthenium-catalyzed Cannizzaro reaction of aromatic aldehydes.
Scheme 9: MgBr2·Et2O-assisted Cannizzaro reaction of aldehydes.
Scheme 10: LiBr-catalyzed intermolecular Cannizzaro reaction of aldehydes.
Scheme 11: γ-Alumina as a catalyst in the Cannizzaro reaction.
Scheme 12: AlCl3-mediated Cannizzaro disproportionation of aldehydes.
Scheme 13: Ru–N-heterocyclic carbene catalyzed dehydrogenative synthesis of carboxylic acids.
Figure 4: Proposed catalytic cycle for the dehydrogenation of alcohols.
Scheme 14: Intramolecular desymmetrization of tetraethylene glycol.
Scheme 15: Desymmetrization of oligoethylene glycol dialdehydes.
Scheme 16: Intramolecular Cannizzaro reaction of calix[4]arene dialdehydes.
Scheme 17: Desymmetrization of dialdehydes of symmetrical crown ethers using Ba(OH)2.
Scheme 18: Synthesis of ottelione A (proposed) via intramolecular Cannizzaro reaction.
Scheme 19: Intramolecular Cannizzaro reaction for the synthesis of pestalalactone.
Scheme 20: Synthetic strategy towards nigricanin involving an intramolecular Cannizzaro reaction.
Scheme 21: Spiro-β-lactone-γ-lactam part of oxazolomycins via aldol crossed-Cannizzaro reaction.
Scheme 22: Synthesis of indole alkaloids via aldol crossed-Cannizzaro reaction.
Scheme 23: Aldol and crossed-Cannizzaro reaction towards the synthesis of ertuliflozin.
Scheme 24: Synthesis of cyclooctadieneones using a Cannizzaro reaction.
Scheme 25: Microwave-assisted crossed-Cannizzaro reaction for the synthesis of 3,3-disubstituted oxindoles.
Scheme 26: Synthesis of porphyrin-based rings using the Cannizzaro reaction.
Scheme 27: Synthesis of phthalides and pestalalactone via Cannizarro–Tishchenko-type reaction.
Scheme 28: Synthesis of dibenzoheptalene bislactones via a double intramolecular Cannizzaro reaction.
Sustainable tandem acylation/Diels–Alder reaction toward versatile tricyclic epoxyisoindole-7-carboxylic acids in renewable green solvents
- Ayhan Yıldırım
Beilstein J. Org. Chem. 2024, 20, 1308–1319, doi:10.3762/bjoc.20.114
- importance in intramolecular Diels–Alder reactions, the effects of solvents such as glycerol, polyethylene glycol, organic carbonates, deep eutectic solvents, supercritical CO2 and H2O have recently been extensively studied [65][66][67]. Recently, attention has also been drawn to photoinduced oxidative [4
Graphical Abstract
Figure 1: Reaction yields after seven uses of SSO and average recovery of the oil.
Scheme 1: Synthesis of epoxyisoindole-7-carboxylic acids 2a–m and 2n–p.
Scheme 2: Possible side reactions of unsaturated fatty acids with maleic anhydride.
Figure 2: Coupling constants of selected protons in compound 2a and its optimized geometric structure.
Scheme 3: Equilibrium of 2n–p with maleamic acid precursors.
Figure 3: Possible mechanism for the IMDAF reaction.
Figure 4: IRC calculations of a) endo-, b) exo-transition structures and products for compound 2a (semi-empir...
Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer
- Mohd Farhan Ansari,
- Atul Kumar Maurya,
- Abhishek Kumar and
- Saravanakumar Elangovan
Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98
- polyethyleneimine derivatives by coupling ethylene glycol and ethylenediamine using manganese-pincer catalyst Mn1 (1 mol %), t-BuOK (10 mol %) in toluene at 150 °C (Scheme 21) [48]. The mechanistic investigation based on the experimental and DFT calculations suggested a BH pathway. First, dehydrogenation of the
- ethylene glycol followed by condensation with ethylenediamine generated the corresponding imine intermediates. The subsequent hydrogenation with borrowed hydrogen finally formed the polyethyleneimine product. In 2023, Royo and co-workers conveyed the N-alkylation of amines with alcohols using the bis
- hydrogenated the C=C and C=O bonds delivering the desired alkylated alcohol products (Scheme 49). Recently, Maji’s group showed environmentally benign examples of the manganese-catalyzed dehydrogenative coupling of ethylene glycol and primary alcohols producing value-added α-hydroxycarboxylic acid molecules
Graphical Abstract
Scheme 1: General scheme of the borrowing hydrogen (BH) or hydrogen auto-transfer (HA) methodology.
Scheme 2: General scheme for C–N bond formation. A) Traditional cross-couplings with alkyl or aryl halides. B...
Figure 1: Manganese pre-catalysts used for the N-alkylation of amines with alcohols.
Scheme 3: Manganese(I)-pincer complex Mn1 used for the N-alkylation of amines with alcohols and methanol.
Scheme 4: N-Methylation of amines with methanol using Mn2.
Scheme 5: C–N-Bond formation with amines and methanol using PN3P-Mn complex Mn3 reported by Sortais et al. [36]. a...
Scheme 6: Base-assisted synthesis of amines and imines with Mn4. Reaction assisted by A) t-BuOK and B) t-BuON...
Scheme 7: Coupling of alcohols and hydrazine via the HB approach reported by Milstein et al. [38]. aReaction time...
Scheme 8: Proposed mechanism for the coupling of alcohols and hydrazine catalyzed by Mn5.
Scheme 9: Phosphine-free manganese catalyst for N-alkylation of amines with alcohols reported by Balaraman an...
Scheme 10: N-Alkylation of sulfonamides with alcohols.
Scheme 11: Mn–NHC catalyst Mn6 applied for the N-alkylation of amines with alcohols. a3 mol % of Mn6 were used....
Scheme 12: N-Alkylation of amines with primary and secondary alcohols. a80 °C, b100 °C.
Scheme 13: Manganese(III)-porphyrin catalyst for synthesis of tertiary amines.
Scheme 14: Proposed mechanism for the alcohol dehydrogenation with Mn(III)-porphyrin complex Mn7.
Scheme 15: N-Methylation of nitroarenes with methanol using catalyst Mn3.
Scheme 16: Mechanism of manganese-catalyzed methylation of nitroarenes using Mn3 as the catalyst.
Scheme 17: Bidentate manganese complex Mn8 applied for the N-alkylation of primary anilines with alcohols. aOn...
Scheme 18: N-Alkylation of amines with alcohols in the presence of manganese salts and triphenylphosphine as t...
Scheme 19: N-Alkylation of diazo compounds with alcohols using catalyst Mn9.
Scheme 20: Proposed mechanism for the amination of alcohols with diazo compounds catalyzed by catalyst Mn9.
Scheme 21: Mn1 complex-catalyzed synthesis of polyethyleneimine from ethylene glycol and ethylenediamine.
Scheme 22: Bis-triazolylidene-manganese complex Mn10 for the N-alkylation of amines with alcohols.
Figure 2: Manganese complexes applied for C-alkylation reactions of ketones with alcohols.
Scheme 23: General scheme for the C–C bond formation with alcohols and ketones.
Scheme 24: Mn1 complex-catalyzed α-alkylation of ketones with primary alcohols.
Scheme 25: Mechanism for the Mn1-catalyzed alkylation of ketones with alcohols.
Scheme 26: Phosphine-free in situ-generated manganese catalyst for the α-alkylation of ketones with primary al...
Scheme 27: Plausible mechanism for the Mn-catalyzed α-alkylation of ketones with alcohols.
Scheme 28: α-Alkylation of esters, ketones, and amides using alcohols catalyzed by Mn11.
Scheme 29: Mono- and dialkylation of methylene ketones with primary alcohols using the Mn(acac)2/1,10-phenanth...
Scheme 30: Methylation of ketones with methanol and deuterated methanol.
Scheme 31: Methylation of ketones and esters with methanol. a50 mol % of t-BuOK were used, bCD3OD was used ins...
Scheme 32: Alkylation of ketones and secondary alcohols with primary alcohols using Mn4.
Scheme 33: Bidentate manganese-NHC complex Mn6 applied for the synthesis of alkylated ketones using alcohols.
Scheme 34: Mn1-catalyzed synthesis of substituted cycloalkanes by coupling diols and secondary alcohols or ket...
Scheme 35: Proposed mechanism for the synthesis of cycloalkanes via BH method.
Scheme 36: Synthesis of various cycloalkanes from methyl ketones and diols catalyze by Mn13. aReaction time wa...
Scheme 37: N,N-Amine–manganese complex (Mn13)-catalyzed alkylation of ketones with alcohols.
Scheme 38: Naphthyridine‑N‑oxide manganese complex Mn14 applied for the alkylation of ketones with alcohols. a...
Scheme 39: Proposed mechanism of the naphthyridine‑N‑oxide manganese complex (Mn14)-catalyzed alkylation of ke...
Scheme 40: α-Methylation of ketones and indoles with methanol using Mn15.
Scheme 41: α-Alkylation of ketones with primary alcohols using Mn16. aNMR yield.
Figure 3: Manganese complexes used for coupling of secondary and primary alcohols.
Scheme 42: Alkylation of secondary alcohols with primary alcohols catalyzed by phosphine-free catalyst Mn17. a...
Scheme 43: PNN-Manganese complex Mn18 for the alkylation of secondary alcohols with primary alcohols.
Scheme 44: Mechanism for the Mn-pincer catalyzed C-alkylation of secondary alcohols with primary alcohols.
Scheme 45: Upgrading of ethanol with methanol for isobutanol production.
Scheme 46: Mn-Pincer catalyst Mn19 applied for the β-methylation of alcohols with methanol. a2.0 mol % of Mn19...
Scheme 47: Functionalized ketones from primary and secondary alcohols catalyzed by Mn20. aMn20 (5 mol %), NaOH...
Scheme 48: Synthesis of γ-disubstituted alcohols and β-disubstituted ketones through Mn9-catalyzed coupling of...
Scheme 49: Proposed mechanism for the Mn9-catalyzed synthesis of γ-disubstituted alcohols and β-disubstituted ...
Scheme 50: Dehydrogenative coupling of ethylene glycol and primary alcohols catalyzed by Mn4.
Scheme 51: Mn18-cataylzed C-alkylation of unactivated esters and amides with alcohols.
Scheme 52: Alkylation of amides and esters using Mn21.
Scheme 53: α-Alkylation of nitriles with primary alcohols using in situ-generated manganese catalyst.
Scheme 54: Proposed mechanism for the α-alkylation of nitriles with primary alcohols.
Scheme 55: Mn9-catalyzed α-alkylation of nitriles with primary alcohols. a1,4-Dioxane was used as solvent, 24 ...
Figure 4: Manganese complexes used for alkylation of heterocyclic compounds.
Scheme 56: Aminomethylation of aromatic compounds with secondary amines and methanol catalyzed by Mn22.
Scheme 57: Regioselective alkylation of indolines with alcohols catalyzed by Mn9. aMn9 (4 mol %), 48 h.
Scheme 58: Proposed mechanism for the C- and N-alkylation of indolines with alcohols.
Scheme 59: C-Alkylation of methyl N-heteroarenes with primary alcohols catalyzed by Mn1. aTime was 60 h.
Scheme 60: C-Alkylation of oxindoles with secondary alcohols.
Scheme 61: Plausible mechanism for the Mn23-catalyzed C-alkylation of oxindoles with secondary alcohols.
Scheme 62: Synthesis of C-3-alkylated products by coupling alcohols with indoles and aminoalcohols.
Scheme 63: C3-Alkylation of indoles using Mn1.
Scheme 64: C-Methylation of indoles with Mn15 and methanol.
Scheme 65: α-Alkylation of 2-oxindoles with primary and secondary alcohols catalyzed by Mn25. aReaction carrie...
Scheme 66: Dehydrogenative alkylation of indolines with Mn1. aMn1 (5.0 mol %) was used.
Scheme 67: Synthesis of bis(indolyl)methane derivatives from indoles and alcohols catalyzed by Mn26. aMn26 (5....
Scheme 68: One-pot synthesis of pyrimidines via BH.
Scheme 69: Synthesis of pyrroles from alcohols and aminoalcohols using Mn4.
Scheme 70: Synthesis of pyrroles via multicomponent reaction catalyzed by Mn12.
Scheme 71: Friedländer quinoline synthesis using an in situ-generated phosphine-free manganese catalyst.
Scheme 72: Quinoline synthesis using bis-N-heterocyclic carbene-manganese catalyst Mn6.
Scheme 73: Quinoline synthesis using manganese(III)-porphyrin catalyst Mn7.
Scheme 74: Manganese-catalyzed tetrahydroquinoline synthesis via borrowing BH.
Scheme 75: Proposed mechanism for the manganese-catalyzed tetrahydroquinoline synthesis.
Scheme 76: Synthesis of C3-alkylated indoles using Mn24.
Scheme 77: Synthesis of C-3-alkylated indoles using Mn1.
Scheme 78: C–C Bond formation by coupling of alcohols and ylides.
Scheme 79: C-Alkylation of fluorene with alcohols catalyzed by Mn24.
Scheme 80: Proposed mechanism for the C-alkylation of fluorene with alcohols catalyzed by Mn24.
Scheme 81: α-Alkylation of sulfones using Mn-PNN catalyst Mn28.
Mild and efficient synthesis and base-promoted rearrangement of novel isoxazolo[4,5-b]pyridines
- Vladislav V. Nikol’skiy,
- Mikhail E. Minyaev,
- Maxim A. Bastrakov and
- Alexey M. Starosotnikov
Beilstein J. Org. Chem. 2024, 20, 1069–1075, doi:10.3762/bjoc.20.94
- group of compounds 7 should be protected prior to the attempted isoxazole ring formation. Indeed, reactions of 7a–c with ethylene glycol gave dioxolane derivatives 9a–c which were converted into isoxazolo[4,5-b]pyridines 10a–c in high yields under mild conditions (Scheme 4). The obtained result prompted
Graphical Abstract
Figure 1: Some examples of biologically active isoxazolo[4,5-b]pyridines with antibacterial [8], anticancer [12] and...
Scheme 1: Methods for the synthesis of isoxazolo[4,5-b]pyridines: (A) annulation of an isoxazole fragment to ...
Scheme 2: Synthesis of ethyl 6-R-isoxazolo[4,5-b]pyridine-3-carboxylates 4a–c.
Scheme 3: Synthesis of isonitroso compounds 7.
Scheme 4: Base-promoted cyclization of compounds 7a–c.
Scheme 5: Synthesis and rearrangement of arylhydrazones 12.
Figure 2: Biologically active analogs of compounds 13.
Figure 3: X-ray crystal structures of compounds 12c (top left; the second crystallographically unique molecul...
Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives
- Tural N. Akhmedov,
- Ajeet Kumar,
- Daken J. Starkenburg,
- Kyle J. Chesney,
- Khalil A. Abboud,
- Novruz G. Akhmedov,
- Jiangeng Xue and
- Ronald K. Castellano
Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92
- , ethanol, ethylene glycol, and diethylene glycol in the presence of excess triethylamine (Scheme 2). These products provide evidence for the in situ formation of DCPQ 7a and demonstrate its ability to undergo trapping with various nucleophiles through an SNAr mechanism. An alternate strategy was employed
- -stacking distances (≈3.2 Å) are observed between the 5b units. For 6b, this is likely due to the included solvent (ethylene glycol) that hydrogen bonds to the quinoxalinedione. Moving forward, 2b stands out as a promising candidate for future solid-state characterization and device fabrication studies
Graphical Abstract
Figure 1: Chemical structures of H-bonding N-heteroacenes synthesized by Miao et al. and Bunz et al. (a) [22,23]. Pr...
Scheme 1: Synthesis of dicyanopyrazinoquinoxaline derivatives 1a–7a.
Scheme 2: Synthesis of bis-alkoxy-substituted π-conjugated phenanthrolines 16a, 16b, 16c, and 16d.
Scheme 3: An alternative synthetic route to access 7a.
Scheme 4: Synthesis of DPQDs 1b–7b from their corresponding DCPQs 1a–7a. *THF/H2O/1,4-dioxane (4:5:1). **in s...
Figure 2: TGA of 1a–6a (a) and 1b–7b (b) obtained at 10 °C/min under nitrogen.
Figure 3: Absorption spectra (20 μM) for a) DCPQs 1a–6a and b) DPQDs 1b–7b in dimethyl sulfoxide.
Figure 4: Calculated HOMO (below) and LUMO (above) energies by DFT analysis (B3LYP/6-31+G* level of theory), ...
Figure 5: Calculated HOMO (below) and LUMO (above) energies by DFT analysis (B3LYP/6-31+G* level of theory), ...
Figure 6: Asymmetric unit of DPQD 2b with important bond lengths highlighted (a). Torsion angles of 4.33° and...
Carbonylative synthesis and functionalization of indoles
- Alex De Salvo,
- Raffaella Mancuso and
- Xiao-Feng Wu
Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87
- the presence of Ni(dme)Cl2 (a nickel(II) chloride ethylene glycol dimethyl ether complex), dtbbpy (4,4-di-tert-butyl-2,2-dipyridyl), Zn(0) and ZnI2 in DMF at 120 °C [42] (Scheme 22). The nickel catalyst catalyzed the oxidative addition and CO insertion on aryl iodide compounds, while the Zn/ZnI2
Graphical Abstract
Scheme 1: Pd(0)-catalyzed domino C,N-coupling/carbonylation/Suzuki coupling reaction for the synthesis of 2-a...
Scheme 2: Pd(0)-catalyzed single isonitrile insertion: synthesis of 1-(3-amino)-1H-indol-2-yl)-1-ketones.
Scheme 3: Pd(0)-catalyzed gas-free carbonylation of 2-alkynylanilines to 1-(1H-indol-1-yl)-2-arylethan-1-ones....
Scheme 4: Pd(II)-catalyzed heterocyclization/alkoxycarbonylation of 2-alkynylaniline imines.
Scheme 5: Pd(II)-catalyzed heterocyclization/alkoxycarbonylation of 2-alkynylanilines to N-substituted indole...
Scheme 6: Synthesis of indol-2-acetic esters by Pd(II)-catalyzed carbonylation of 1-(2-aminoaryl)-2-yn-1-ols.
Scheme 7: Pd(II)-catalyzed carbonylative double cyclization of suitably functionalized 2-alkynylanilines to 3...
Scheme 8: Indole synthesis by deoxygenation reactions of nitro compounds reported by Cenini et al. [21].
Scheme 9: Indole synthesis by reduction of nitro compounds: approach reported by Watanabe et al. [22].
Scheme 10: Indole synthesis from o-nitrostyrene compounds as reported by Söderberg and co-workers [23].
Scheme 11: Synthesis of fused indoles (top) and natural indoles present in two species of European Basidiomyce...
Scheme 12: Synthesis of 1,2-dihydro-4(3H)-carbazolones through N-heteroannulation of functionalized 2-nitrosty...
Scheme 13: Synthesis of indoles from o-nitrostyrenes by using Pd(OAc)2 and Pd(tfa)2 in conjunction with bident...
Scheme 14: Synthesis of substituted 3-alkoxyindoles via palladium-catalyzed reductive N-heteroannulation.
Scheme 15: Synthesis of 3-arylindoles by palladium-catalyzed C–H bond amination via reduction of nitroalkenes.
Scheme 16: Synthesis of 2,2′-bi-1H-indoles, 2,3′-bi-1H-indoles, 3,3′-bi-1H-indoles, indolo[3,2-b]indoles, indo...
Scheme 17: Pd-catalyzed reductive cyclization of 1,2-bis(2-nitrophenyl)ethene and 1,1-bis(2-nitrophenyl)ethene...
Scheme 18: Flow synthesis of 2-substituted indoles by reductive carbonylation.
Scheme 19: Pd-catalyzed synthesis of variously substituted 3H-indoles from nitrostyrenes by using Mo(CO)6 as C...
Scheme 20: Synthesis of indoles from substituted 2-nitrostyrenes (top) and ω-nitrostyrenes (bottom) via reduct...
Scheme 21: Synthesis of indoles from substituted 2-nitrostyrenes with formic acid as CO source.
Scheme 22: Ni-catalyzed carbonylative cyclization of 2-nitroalkynes and aryl iodides (top) and the Ni-catalyze...
Scheme 23: Mechanism of the Ni-catalyzed carbonylative cyclization of 2-nitroalkynes and aryl iodides (top) an...
Scheme 24: Route to indole derivatives through Rh-catalyzed benzannulation of heteroaryl propargylic esters fa...
Scheme 25: Pd-catalyzed cyclization of 2-(2-haloaryl)indoles reported by Yoo and co-workers [54], Guo and co-worke...
Scheme 26: Approach for the synthesis of 6H-isoindolo[2,1-a]indol-6-ones reported by Huang and co-workers [57].
Scheme 27: Zhou group’s method for the synthesis of 6H-isoindolo[2,1-a]indol-6-ones.
Scheme 28: Synthesis of 6H-isoindolo[2,1-a]indol-6-ones from o-1,2-dibromobenzene and indole derivatives by us...
Scheme 29: Pd(OAc)2-catalyzed Heck cyclization of 2-(2-bromophenyl)-1-alkyl-1H-indoles reported by Guo et al. [55]....
Scheme 30: Synthesis of indolo[1,2-a]quinoxalinone derivatives through Pd/Cu co-catalyzed carbonylative cycliz...
Scheme 31: Pd-catalyzed carbonylative cyclization of o-indolylarylamines and N-monosubstituted o-indolylarylam...
Scheme 32: Pd-catalyzed diasteroselective carbonylative cyclodearomatization of N-(2-bromobenzoyl)indoles with...
Scheme 33: Pd(0)-catalyzed synthesis of CO-linked heterocyclic scaffolds from alkene-indole derivatives and 2-...
Scheme 34: Proposed mechanism for the Pd(0)-catalyzed synthesis of CO-linked heterocyclic scaffolds.
Scheme 35: Pd-catalyzed C–H and N–H alkoxycarbonylation of indole derivatives to indole-3-carboxylates and ind...
Scheme 36: Rh-catalyzed C–H alcoxycarbonylation of indole derivatives to indole-3-carboxylates reported by Li ...
Scheme 37: Pd-catalyzed C–H alkoxycarbonylation of indole derivatives with alcohols and phenols to indole-3-ca...
Scheme 38: Synthesis of N-methylindole-3-carboxylates from N-methylindoles and phenols through metal-catalyst-...
Scheme 39: Synthesis of indol-3-α-ketoamides (top) and indol-3-amides (bottom) via direct double- and monoamin...
Scheme 40: The direct Sonogashira carbonylation coupling reaction of indoles and alkynes via Pd/CuI catalysis ...
Scheme 41: Synthesis of indole-3-yl aryl ketones reported by Zhao and co-workers [73] (path a) and Zhang and co-wo...
Scheme 42: Pd-catalyzed carbonylative synthesis of BIMs from aryl iodides and N-substituted and NH-free indole...
Scheme 43: Cu-catalyzed direct double-carbonylation and monocarbonylation of indoles and alcohols with hexaket...
Scheme 44: Rh-catalyzed direct C–H alkoxycarbonylation of indoles to indole-2-carboxylates [79] (top) and Co-catal...
Scheme 45: Pd-catalyzed carbonylation of NH free-haloindoles.
Synthesis and characterization of water-soluble C60–peptide conjugates
- Yue Ma,
- Lorenzo Persi and
- Yoko Yamakoshi
Beilstein J. Org. Chem. 2024, 20, 777–786, doi:10.3762/bjoc.20.71
- -soluble C60 and C70 derivatives by covalently attaching biocompatible water-soluble polymers, such as polyethylene glycol (PEG) [37][38] and PVP [39]. Although these C60– and C70–polymer conjugates revealed high water-solubility, it was found that they, especially the PEG conjugates, formed micelle-like
Graphical Abstract
Figure 1: a) Synthesis of C60–oligopeptide conjugates 5a–c and b) synthesis of compound 3. Fulleropyrrolidine...
Figure 2: Structure of C60–oligo-Lys (5a), C60–oligo-Glu (5b), and C60–oligo-Arg (5c) and images of dissolved...
Figure 3: DLS diagrams of C60–peptide conjugates 5a (1 mM, in Milli-Q® water), 5b (1 mM, in Milli-Q® water or...
Figure 4: UV–vis spectra of C60–peptide conjugates 5a and 5b (20 μM in Milli-Q® water for 5a and in pH 9.0 TR...
Figure 5: 1H NMR spectrum of C60–peptide conjugate 5a in D2O (above) and of the precursor monoadduct in CDCl3...
Figure 6: 13C NMR spectrum of C60–peptide conjugate 5a in D2O and of the precursor monoadduct in CDCl3 at 150...
Figure 7: a) X-band ESR spectra of the 4-oxo-TEMP adduct with 1O2 generated by C60–oligo-Lys (5a) and rose be...
Synthesis of new representatives of A3B-type carboranylporphyrins based on meso-tetra(pentafluorophenyl)porphyrin transformations
- Victoria M. Alpatova,
- Evgeny G. Rys,
- Elena G. Kononova and
- Valentina A. Ol'shevskaya
Beilstein J. Org. Chem. 2024, 20, 767–776, doi:10.3762/bjoc.20.70
- -dioxaoctane (21) and 1,13-diamino-4,7,10-trioxatridecane (22) in DMSO at 70 °C for 30 min to form amino-conjugates 23 and 24 in 71 and 84% yield, respectively, containing ethylene glycol linkers with terminal primary amino groups (Scheme 6). The presence of ethylene glycol residues in bioactive molecules is
Graphical Abstract
Scheme 1: Synthesis of porphyrins 2 and 3.
Scheme 2: Synthesis of carborane aminoporphyrin 5.
Scheme 3: Synthesis of carboranyl-substituted porphyrins 5–7.
Scheme 4: Synthesis of acylated carboranylporphyrins 11, 12, and 14.
Scheme 5: Synthesis of thio-substituted carboranylporphyrins 18–20.
Scheme 6: Synthesis of amino-substituted carboranylporphyrins 23, 24, and 26.
Chemoenzymatic synthesis of macrocyclic peptides and polyketides via thioesterase-catalyzed macrocyclization
- Senze Qiao,
- Zhongyu Cheng and
- Fuzhuo Li
Beilstein J. Org. Chem. 2024, 20, 721–733, doi:10.3762/bjoc.20.66
- and promote the utilization of TE domains as biocatalysts with tremendous potential. To this purpose, Walsh and co-workers developed the 2nd generation of tyrocidine chemoenzymatic approach utilizing a linear peptide immobilized on the solid-phase support poly(ethylene glycol) acrylate (PEGA) with a
- exhibits a cyclization activity against a peptide methyl ester that is feeble but readily detectable [61]. This finding indicates that SurE has a high tolerance for leaving groups. In the light of this property, Wakimoto, Matsuda, and co-workers discovered that ethylene glycol (EG) can act as a linker on
- manner catalyzed by homolog WolJ [63] and SurE G235L (Scheme 5b). Additionally, the above mentioned type I TE, TycC TE, can also tolerate ethylene glycol as a leaving group and gave tyrocidine A (1) in 70% yield, indicating that this convenient bifunctional linker may have a comparable applied range to N
Graphical Abstract
Scheme 1: Brief introduction of thioesterase (TE) domain. (a) NRPS and PKS assembly lines. (b) Mechanism of T...
Scheme 2: Chemoenzymatic synthesis of tyrocidine A and its analogs. (a) First-gen chemoenzymatic synthesis of...
Scheme 3: Representative examples of NAC-activated thioesters-mediated biocatalytic macrolactamization.
Scheme 4: Chemoenzymatic synthesis of CDA, daptomycin and their analogs. (a) Biocatalytic macrocyclization of...
Scheme 5: Chemoenzymatic synthesis of surugamide B and related natural products. (a) Three synthetic strategi...
Scheme 6: Chemoenzymatic synthesis of the pikromycins. (a) Macrocyclization of 10-deoxymethynolide catalyzed ...
Scheme 7: Chemoenzymatic synthesis of the juevnimicins.
Scheme 8: Chemoenzymatic synthesis of the cryptophycins.
Switchable molecular tweezers: design and applications
- Pablo Msellem,
- Maksym Dekthiarenko,
- Nihal Hadj Seyd and
- Guillaume Vives
Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45
- sites was developed concomitantly to the nitrogen-based systems. In 1999, Boschi and co-workers reported the podand-based switchable tweezers 31 (Figure 17) [66]. This kind of spacer is flexible due to the ethylene glycol chain but can complex alkali cations like crown ethers. Upon complexation, the
Graphical Abstract
Figure 1: Principle of switchable molecular tweezers.
Figure 2: Principle of pH-switchable molecular tweezers 1 [19].
Figure 3: a) pH-Switchable tweezers 2 substituted with alkyl chains as switchable lipids. b) Schematic depict...
Figure 4: Modification of spectral properties of 3 by controlled induction of Pt–Pt interactions.
Figure 5: Conformational switching of di(hydroxyphenyl)pyrimidine-based tweezer 4 upon alkylation or fluoride...
Figure 6: Hydrazone-based pH-responsive tweezers 5 for mesogenic modulation.
Figure 7: pH-Switchable molecular tweezers 6 bearing acridinium moieties.
Figure 8: a) Terpyridine and pyridine-hydrazone-pyridine analogs molecular tweezers and b) extended pyridine ...
Figure 9: Terpyridine-based molecular tweezers with M–salphen arms and their field of application. Figure 9 was adapt...
Figure 10: a) Terpyridine-based molecular tweezers for diphosphate recognition [48]; b) bishelicene chiroptical te...
Figure 11: Terpyridine-based molecular tweezers with allosteric cooperative binding.
Figure 12: Terpyridine-based molecular tweezers presenting closed by default conformation.
Figure 13: Pyridine-pyrimidine-pyridine-based molecular tweezers.
Figure 14: Coordination-responsive molecular tweezers based on nitrogen-containing ligands.
Figure 15: Molecular tweezers exploiting the remote bipyridine or pyridine binding to trigger the conformation...
Figure 16: Bipyridine-based molecular tweezers exploiting the direct s-trans to s-cis-switching for a) anion b...
Figure 17: a) Podand-based molecular tweezers [66,67]. b) Application of tweezers 32 for the catalytic allosteric reg...
Figure 18: Anion-triggered molecular tweezers based on calix[4]pyrrole.
Figure 19: Anion-triggered molecular tweezers.
Figure 20: a) Principle of the weak link approach (WLA) developed by Mirkin and its application to b) symmetri...
Figure 21: Molecular tweezers as allosteric catalyst in asymmetric epoxide opening [80].
Figure 22: Allosteric regulation of catalytic activity in ring-opening polymerization with double tweezers 41.
Figure 23: a) Conformational switching of 42 by intramolecular –S–S– bridge formation. b) Shift of conformatio...
Figure 24: a) Redox-active glycoluril-TTF tweezers 44. b) Mechanism of stepwise oxidation of said tweezers wit...
Figure 25: Mechanism of formation of the mixed-valence dimers of tweezers 45.
Figure 26: Mechanism of carbohydrate liberation upon redox-mediated conformation switching of 46.
Figure 27: a) The encapsulation properties of 47 as well as the DCTNF release process from its host–guest comp...
Figure 28: Redox-active bipyridinium-based tweezers. a) With a ferrocenyl hinge 49, b) with a propyl hinge 50 ...
Figure 29: Redox-active calix[4]arene porphyrin molecular tweezers.
Figure 30: a) Mechanism of the three orthogonal stimuli. b) Cubic scheme showing the eight different states of ...
Figure 31: Redox-controlled molecular gripper based on a diquinone resorcin[4]arene.
Figure 32: a) Shinkai's butterfly tweezers and their different host–guest properties depending on the isomer. ...
Figure 33: Cyclam-tethered tweezers and their different host–guest complexes depending on their configuration.
Figure 34: Azobenzene-based catalytic tweezers.
Figure 35: Photoswitchable PIEZO channel mimic.
Figure 36: Stilbene-based porphyrin tweezers for fullerene recognition.
Figure 37: Stiff-stilbene-based tweezers with urea or thiourea functional units for a) anion binding, b) anion...
Figure 38: Feringa’s photoswitchable organocatalyst (a) and different catalyzed reactions with that system (b)....
Figure 39: a) Irie and Takeshita’s thioindigo-based molecular tweezers. b) Family of hemithioindigo-based mole...
Figure 40: Dithienylethylene crown ether-bearing molecular tweezers reported by Irie and co-workers.
Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles
- Periklis X. Kolagkis,
- Eirini M. Galathri and
- Christoforos G. Kokotos
Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36
- , depending on the substrate used, with both aromatic and aliphatic aldehydes reaching conversion rates of 98% (Scheme 23). In 2021, a methodology making use of poly(ethylene glycol)-supported Fe3O4 nanoparticles was reported by Mardani et al., who managed to remove the need for conventional heating. 10 mg of
Graphical Abstract
Scheme 1: Examples of BIMs used for their medicinal properties.
Scheme 2: Mechanisms for the synthesis of BIMs using protic or Lewis acids as catalysts.
Scheme 3: Synthesis of bis(indolyl)methanes using DBDMH.
Scheme 4: Competition experiments and synthesis of bis(indolyl)methanes using DBDMH.
Scheme 5: Proposed mechanism for formation of BIM of using DBDMH.
Scheme 6: Synthesis of bis(indolyl)methanes using I2.
Scheme 7: General reaction mechanism upon halogen bonding.
Scheme 8: Synthesis of bis(indolyl)methanes using I2, introduced by Ji.
Scheme 9: Synthesis of bis(indolyl)methanes using Br2 in CH3CN.
Scheme 10: Βidentate halogen-bond donors.
Scheme 11: Synthesis of bis(indolyl)methanes using bidentate halogen-bond donor 26.
Scheme 12: Proposed reaction mechanism.
Scheme 13: Synthesis of bis(indolyl)methanes using iodoalkyne as catalyst.
Scheme 14: Proposed reaction mechanism.
Scheme 15: Optimized reaction conditions used by Ramshini.
Scheme 16: Activation of the carbonyl group by HPA/TPI-Fe3O4.
Scheme 17: Synthesis of BIMs in the presence of nanoAg-Pt/SiO2-doped silicate.
Scheme 18: Mechanism of action proposed by Khalafi-Nezhad et al.
Scheme 19: Activation of the carbonyl group by the Cu–isatin Schiff base complex.
Scheme 20: Optimum reaction conditions published by Jain.
Scheme 21: Organocatalytic protocol utilizing nanoparticles introduced by Bankar.
Scheme 22: Activation of the carbonyl group by the AlCl3·6H2O-SDS-SiO2 complex.
Scheme 23: Optimal reaction conditions for the aforementioned nano-Fe3O4 based catalysts.
Scheme 24: Nanocatalytic protocol proposed by Kaur et al.
Scheme 25: Microwave approach introduced by Yuan.
Scheme 26: Microwave approach introduced by Zahran et al.
Scheme 27: Microwave irradiation protocol introduced by Bindu.
Scheme 28: Silica-supported microwave irradiation protocol.
Scheme 29: Proposed mechanism for formation of BIM by Nongkhlaw.
Scheme 30: Microwave-assisted synthesis of BIMs catalyzed by succinic acid.
Scheme 31: Proposed mechanism of action of MMO-4.
Scheme 32: Catalytic approach introduced by Muhammadpoor-Baltork et al.
Scheme 33: Reaction conditions used by Xiao-Ming.
Scheme 34: Ultrasonic irradiation-based protocol published by Saeednia.
Scheme 35: Pyruvic acid-mediated synthesis of BIMs proposed by Thopate.
Scheme 36: Synthesis of BIMs using [bmim]BF4 or [bmim]PF6 ionic liquids.
Scheme 37: Synthesis of BIMs utilizing In(OTf)3 in octylmethylimidazolium hexafluorophosphate as ionic liquid.
Scheme 38: FeCl3·6H2O-catalyzed synthesis of BIMs with use of ionic liquid.
Scheme 39: Synthesis of BIMs utilizing the [hmim]HSO4/EtOH catalytic system.
Scheme 40: Synthesis of BIMs utilizing acidic ionic liquid immobilized on silica gel (ILIS-SO2Cl).
Scheme 41: The [bmim][MeSO4]-catalyzed reaction of indole with various aldehydes.
Scheme 42: The role of [bmim][MeSO4] in catalyzing the reaction of indole with aldehydes.
Scheme 43: Synthesis of BIMs utilizing FeCl3-based ionic liquid ([BTBAC]Cl-FeCl3) as catalyst.
Scheme 44: Synthesis of BIMs using [Msim]Cl at room temperature.
Scheme 45: [Et3NH][H2PO4]-catalyzed synthesis of bis(indolyl)methanes.
Scheme 46: PILs-catalyzed synthesis of bis(indolyl)methanes.
Scheme 47: FSILs-mediated synthesis of bis(indolyl)methanes.
Scheme 48: Possible “release and catch” catalytic process.
Scheme 49: Synthesis of bis(indolyl)methanes by [DABCO-H][HSO4].
Scheme 50: Synthesis of bis(indolyl)methanes by [(THA)(SO4)].
Scheme 51: Synthesis of BBSI-Cl and BBSI-HSO4.
Scheme 52: Synthesis of BIMs in the presence of BBSI-Cl and BBSI-HSO4.
Scheme 53: Chemoselectivity of the present method.
Scheme 54: Synthesis of BIMs catalyzed by chitosan-supported ionic liquid.
Scheme 55: Proposed mechanism of action of CSIL.
Scheme 56: Optimization of the reaction in DESs.
Scheme 57: Synthesis of BIMs using ChCl/SnCl2 as DES.
Scheme 58: Synthesis of BIMs derivatives in presence of DES.
Scheme 59: BIMs synthesis in choline chloride/urea (CC/U).
Scheme 60: Flow chemistry-based synthesis of BIMs by Ley.
Scheme 61: Flow chemistry-based synthesis of BIMs proposed by Nam et al.
Scheme 62: Amino-catalyzed reaction of indole with propionaldehyde.
Scheme 63: Aminocatalytic synthesis of BIMs.
Scheme 64: Proposed mechanism for the aminocatalytic synthesis of BIMs.
Scheme 65: Enzymatic reaction of indole with aldehydes.
Scheme 66: Proposed mechanism for the synthesis of BIMs catalyzed by TLIM.
Scheme 67: Proposed reaction mechanism by Badsara.
Scheme 68: Mechanism proposed by D’Auria.
Scheme 69: Photoinduced thiourea catalysis.
Scheme 70: Proposed mechanism of photoacid activation.
Scheme 71: Proposed mechanism of action for CF3SO2Na.
Scheme 72: Proposed mechanism for the synthesis of BIMs by Mandawad.
Scheme 73: Proposed mechanism for the (a) acid generation and (b) synthesis of BIMs.
Scheme 74: a) Reaction conditions employed by Khaksar and b) activation of the carbonyl group by HFIP.
Scheme 75: Activation of the carbonyl group by the PPy@CH2Br through the formation of a halogen bond.
Scheme 76: Reaction conditions utilized by Mhaldar et al.
Scheme 77: a) Reaction conditions employed by López and b) activation of the carbonyl group by thiourea.
Scheme 78: Infrared irradiation approach introduced by Luna-Mora and his research group.
Scheme 79: Synthesis of BIMs with the use of the Fe–Zn BMOF.
Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units
- Christina Schøttler,
- Kasper Lund-Rasmussen,
- Line Broløs,
- Philip Vinterberg,
- Ema Bazikova,
- Viktor B. R. Pedersen and
- Mogens Brøndsted Nielsen
Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8
- , dithranol, m/z) [M•+] calcd for C82H102S4Si2•+, 956.3572; found, 956.3620. Compound 29 To a 250 mL round-bottomed flask equipped with a reflux condenser and containing a magnetic stir bar, diethylene glycol (125 mL) and KOH (2.67 g, 47.7 mmol) were added. The solution was degassed with Ar for 30 min after
Graphical Abstract
Figure 1: Overview of structural motifs relevant for the work described herein.
Figure 2: Dione/ketones 1, 4–6 and 1,3-dithiole-2-thione compounds 2, 3, 7, and 8 are building blocks used in...
Scheme 1: Synthesis of IF-DTF ketones 9–12 and dimer 13.
Scheme 2: Further functionalization of the IF-DTF ketone 11 via Ramirez/Corey–Fuchs dibromo-olefination and K...
Scheme 3: Coupling of 1,3-dithiole-2-thione building blocks 2 and 3 with fluorenone 5 to afford fluorene-exte...
Scheme 4: Synthesis of acetylenic scaffolds based on IF-DTF. Conditions: (a) Pd(PPh3)2Cl2, CuI, THF, Et3N, rt...
Scheme 5: Synthesis of acetylenic scaffolds with IF as central core. *Not fully characterized due to poor sol...
Scheme 6: Reduction of IF dione 1 to dihydro-IF 29.
Figure 3: UV–vis absorption spectra of compounds 4, 9–12, and 15 in PhMe at 25 °C.
Figure 4: UV–vis absorption spectra of compounds 13, 16, 17, and 30 in CH2Cl2 at 25 °C.
Figure 5: UV–vis absorption spectra of compounds 22, 23, 26, and 27 in CH2Cl2 at 25 °C.
Figure 6: Cyclic voltammograms of compounds 11 (in MeCN), 13 (in CH2Cl2), 15 (in MeCN), 16 (in CH2Cl2), and 17...
Figure 7: Comparison of properties of compounds 13 and 17.
Figure 8: Cyclic voltammograms of compounds 22, 23, 26, and 27 in CH2Cl2; supporting electrolyte: 0.1 M Bu4NPF...
Figure 9: Radical anion (left), dianion (middle), and radical cation (right) of compound 23; the radical anio...
Figure 10: ORTEP plots (50% probability) and crystal packing of compounds a) 25, b) 26, and c) 29. The respect...
Figure 11: Labels of bonds within five-membered ring.
Tying a knot between crown ethers and porphyrins
- Maksym Matviyishyn and
- Bartosz Szyszko
Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120
- oligo(ethylene glycol) segment. These hybrid systems constitute a broad group of compounds, including crowned porphyrins, crownphyrins, and calixpyrrole-crown ether systems forming Pacman complexes with transition metals. Their unique nature accustoms them as excellent ligands and hosts capable of
- the molecule, i.e., at the β- or meso-positions. The other is constituted by molecules wherein the principal structural element of the porphyrin framework is connected with the oligo(ethylene glycol) chain forming the macrocycle. The examples briefly referred to in this chapter will be described in
- another group of hybrid macrocycles in which the dipyrrin is connected to oligo(ethylene glycol) through carbon–carbon bonds [68]. In 2022, our group demonstrated the synthesis and reactivity of crownphyrins – hybrid macrocycles wherein the dipyrrin segment links with the crown ether part through the
Graphical Abstract
Figure 1: Porphyrin and crown ether.
Figure 2: Timeline demonstrating the contributions into the crown ether–porphyrin chemistry.
Figure 3: Tetra-crowned porphyrin 1 and dimer 2 formed upon K+ binding.
Figure 4: meso-Crowned 25-oxasmaragdyrins 3a–c and their boron(III) complexes (3a–c)-BF2.
Scheme 1: CsF ion-pair binding of 4. The molecular structure of 4-CsF is shown on the right [101].
Figure 5: CsF ion pair binding by 5. The molecular structure of 5-CsF is shown on the right [102].
Scheme 2: Ion-pair binding by 6. The molecular structure of (6-CsCl)2 is shown on the right [103].
Scheme 3: Hydrated fluoride binding by 7 [104].
Figure 6: β-Crowned porphyrin 8.
Figure 7: Crown ether-capped porphyrins 9.
Figure 8: The capped porphyrin 10 and complex [10-PQ](PF6)2.
Figure 9: The double-capped porphyrin 11.
Figure 10: Selected examples of iminoporphyrinoids [58,122].
Scheme 4: The synthesis of 13.
Scheme 5: Tripyrrane-based crown ether-embedding porphyrinoid 15.
Figure 11: Macrocycles 16–19 and their coordination compounds.
Scheme 6: The flexibility of 16-Co [66].
Figure 12: Hexagonal wheel composed of six 16-Co(III) monomers [66].
Scheme 7: The synthesis of 16-V [67].
Figure 13: The molecular structure of dimers [16-Mn]2 [67].
Scheme 8: Synthesis of crownphyrins 28–33. Compounds 23a/b and 29a/b were obtained from 4,7,10-trioxa-1,13-tr...
Figure 14: The molecular structures of 22a, 34a·(HCl)2, and 29b [69].
Figure 15: Molecular structures of 22a-Pb and (29b)2-Zn [69].
Scheme 9: Reactivity of 29a/b.
Scheme 10: Synthesis of 36 and 37 [131].
Scheme 11: Synthesis of 40–45.
Figure 16: Potential applications of porphyrin-crown ether hybrids.
Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review
- Nosheen Beig,
- Varsha Goyal and
- Raj K. Bansal
Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102
- ) complex, [(IPr)CuCl] (Scheme 69). Hong and co-workers [92] developed diethylene glycol-functionalized imidazo[1,5,a]pyridin-3-ylidenes (DEG-ImPy) as a bifunctional NHC ligand. The Cu catalyst generated in situ with the DEG-ImPy·HCl salt 182 efficiently catalyzed direct C–H carboxylation of various
Graphical Abstract
Scheme 1: In situ generation of imidazolylidene carbene.
Scheme 2: Hg(II) complex of NHC.
Scheme 3: Isolable and bottlable carbene reported by Arduengo [3].
Scheme 4: First air-stable carbene synthesized by Arduengo in 1992 [5].
Figure 1: General structure of an NHC.
Figure 2: Stabilization of an NHC by donation of the lone pair electrons into the vacant p-orbital (LUMO) at ...
Figure 3: Abnormal NHC reported by Bertrand [8,9].
Figure 4: Cu(d) orbital to σ*C-N(NHC) interactions in NHC–CuX complexes computed at the B3LYP/def2-SVP level ...
Figure 5: Molecular orbital contributions to the NHC–metal bond.
Scheme 5: Synthesis of NHC–Cu(I) complexes by deprotonation of NHC precursors with a base.
Scheme 6: Synthesis of [NHC–CuX] complexes.
Scheme 7: Synthesis of [(ICy)CuX] and [(It-Bu)CuX] complexes.
Scheme 8: Synthesis of iodido-bridged copper–NHC complexes by deprotonation of benzimidazolium salts reported...
Scheme 9: Synthesis of copper complexes by deprotonation of triazolium salts.
Scheme 10: Synthesis of thiazolylidene–Cu(I) complex by deprotonation with KOt-Bu.
Scheme 11: Preparation of NHC–Cu(I) complexes.
Scheme 12: Synthesis of methylmalonic acid-derived anionic [(26a,b)CuCl]Li(THF)2 and zwitterionic (28) heterol...
Scheme 13: Synthesis of diaminocarbene and diamidocarbene (DAC)–Cu(I) complexes.
Scheme 14: Synthesis of the cationic (NHC)2Cu(I) complex 39 from benzimidazolium salts 38 with tetrakis(aceton...
Scheme 15: Synthesis of NHC and ADC (acyclic diamino carbenes) Cu(I) hexamethyldisilazide complexes reported b...
Scheme 16: Synthesis of NHC–copper(I) complexes using an acetylacetonate-functionalized imidazolium zwitterion...
Scheme 17: Synthesis of NHC–Cu(I) complexes through deprotonation of azolium salts with Cu2O.
Scheme 18: Synthesis of NHC–CuBr complex through deprotonation with Cu2O reported by Kolychev [31].
Scheme 19: Synthesis of chiral NHC–CuBr complexes from phenoxyimine-imidazolium salts reported by Douthwaite a...
Scheme 20: Preparation of linear neutral NHC–CuCl complexes through the use of Cu2O. For abbreviations, please...
Scheme 21: Synthesis of abnormal-NHC–copper(I) complexes by Bertrand, Cazin and co-workers [35].
Scheme 22: Microwave-assisted synthesis of thiazolylidene/benzothiazolylidene–CuBr complexes by Bansal and co-...
Scheme 23: Synthesis of NHC–CuX complexes through transmetallation.
Scheme 24: Preparation of six- or seven-membered NHC–Cu(I) complexes through transmetalation from Ag(I) comple...
Scheme 25: Synthesis of 1,2,3-triazolylidene–CuCl complexes through transmetallation of Ag(I) complexes genera...
Scheme 26: Synthesis of NHC–copper complexes having both Cu(I) and Cu(II) units through transmetalation report...
Scheme 27: Synthesis of new [(IPr(CH2)3Si(OiPr)3)CuX] complexes and anchoring on MCM-41.
Scheme 28: Synthesis of bis(trimethylsilyl)phosphide–Cu(I)–NHC complexes through ligand displacement.
Scheme 29: Synthesis of silyl- and stannyl [(NHC)Cu−ER3] complexes.
Scheme 30: Synthesis of amido-, phenolato-, thiophenolato–Cu(NHC) complexes.
Scheme 31: Synthesis of first isolable NHC–Cu–difluoromethyl complexes reported by Sanford et al. [44].
Scheme 32: Synthesis of NHC–Cu(I)–bifluoride complexes reported by Riant, Leyssens and co-workers [45].
Scheme 33: Conjugate addition of Et2Zn to enones catalyzed by an NHC–Cu(I) complex reported by Woodward in 200...
Scheme 34: Hydrosilylation of a carbonyl group.
Scheme 35: NHC–Cu(I)-catalyzed hydrosilylation of ketones reported by Nolan et al. [48,49].
Scheme 36: Application of chiral NHC–CuCl complex 104 for the enantioselective hydrosilylation of ketones.
Scheme 37: Hydrosilylation reactions catalyzed by NHC–Cu(Ot-Bu) complexes.
Scheme 38: NHC–CuCl catalyzed carbonylative silylation of alkyl halides.
Scheme 39: Nucleophilic conjugate addition to an activated C=C bond.
Figure 6: Molecular electrostatic potential maps (MESP) of two NHC–CuX complexes computed at the B3LYP/def2-S...
Scheme 40: Conjugate addition of Grignard reagents to 3-alkyl-substituted cyclohexenones catalyzed by a chiral...
Scheme 41: NHC–copper complex-catalyzed conjugate addition of Grignard reagent to 3-substituted hexenone repor...
Scheme 42: Conjugate addition or organoaluminum reagents to β-substituted cyclic enones.
Scheme 43: Conjugate addition of boronates to acyclic α,β-unsaturated carboxylic esters, ketones, and thioeste...
Scheme 44: NHC–Cu(I)-catalyzed hydroboration of an allene reported by Hoveyda [63].
Scheme 45: Conjugate addition of Et2Zn to cyclohexenone catalyzed by NHC–Cu(I) complex derived from benzimidaz...
Scheme 46: Asymmetric conjugate addition of diethylzinc to 3-nonen-2-one catalyzed by NHC–Cu complexes derived...
Scheme 47: General scheme of a [3 + 2] cycloaddition reaction.
Scheme 48: [3 + 2] Cycloaddition of azides with alkynes catalyzed by NHC–Cu(I) complexes reported by Diez-Gonz...
Scheme 49: Application of NHC–CuCl/N-donor combination to catalyze the [3 + 2] cycloaddition of benzyl azide w...
Scheme 50: [3 + 2] Cycloaddition of azides with acetylenes catalyzed by bis(NHC)–Cu complex 131 and mixed NHC–...
Figure 7: NHC–CuCl complex 133 as catalyst for the [3 + 2] cycloaddition of alkynes with azides at room tempe...
Scheme 51: [3 + 2] Cycloaddition of a bulky azide with an alkynylpyridine using [(NHC)Cu(μ-I)2Cu(NHC)] copper ...
Scheme 52: [3 + 2] Cycloaddition of benzyl azide with phenylacetylene under homogeneous and heterogeneous cata...
Scheme 53: [3 + 2] Cycloaddition of benzyl azide with acetylenes catalyzed by bisthiazolylidene dicopper(I) co...
Figure 8: Copper (I)–NHC linear coordination polymer 137 and its conversion into tetranuclear (138) and dinuc...
Scheme 54: An A3 reaction.
Scheme 55: Synthesis of SiO2-immobilized NHC–Cu(I) catalyst 141 and its application in the A3-coupling reactio...
Scheme 56: Preparation of dual-purpose Ru@SiO2–[(NHC)CuCl] catalyst system 142 developed by Bordet, Leitner an...
Scheme 57: Application of the catalyst system Ru@SiO2–[Cu(NHC)] 142 to the one-pot tandem A3 reaction and hydr...
Scheme 58: A3 reaction of phenylacetylene with secondary amines and aldehydes catalyzed by benzothiazolylidene...
Figure 9: Kohn–Sham HOMOs of phenylacetylene and NHC–Cu(I)–phenylacetylene complex computed at the B3LYP/def2...
Figure 10: Energies of the FMOs of phenylacetylene, iminium ion, and NHC–Cu(I)–phenylacetylene complex compute...
Scheme 59: NHC–Cu(I) catalyzed diboration of ketones 147 by reacting with bis(pinacolato)diboron (148) reporte...
Scheme 60: Protoboration of terminal allenes catalyzed by NHC–Cu(I) complexes reported by Hoveyda and co-worke...
Scheme 61: NHC–CuCl-catalyzed borylation of α-alkoxyallenes to give 2-boryl-1,3-butadienes.
Scheme 62: Regioselective hydroborylation of propargylic alcohols and ethers catalyzed by NHC–CuCl complexes 1...
Scheme 63: NHC–CuOt-Bu-catalyzed semihydrogenation and hydroborylation of alkynes.
Scheme 64: Enantioselective NHC–Cu(I)-catalyzed hydroborations of 1,1-disubstituted aryl olefins reported by H...
Scheme 65: Enantioselective NHC–Cu(I)-catalyzed hydroboration of exocyclic 1,1-disubstituted alkenes reported ...
Scheme 66: Markovnikov-selective NHC–CuOH-catalyzed hydroboration of alkenes and alkynes reported by Jones et ...
Scheme 67: Dehydrogenative borylation and silylation of styrenes catalyzed by NHC–CuOt-Bu complexes developed ...
Scheme 68: N–H/C(sp2)–H carboxylation catalyzed by NHC–CuOH complexes.
Scheme 69: C–H Carboxylation of benzoxazole and benzothiazole derivatives with CO2 using a 1,2,3-triazol-5-yli...
Scheme 70: Use of Cu(I) complex derived from diethylene glycol-functionalized imidazo[1,5,a] pyridin-3-ylidene...
Scheme 71: Allylation and alkenylation of polyfluoroarenes and heteroarenes catalyzed by NHC–Cu(I) complexes r...
Scheme 72: Enantioselective C(sp2)–H allylation of (benz)oxazoles and benzothiazoles with γ,γ-disubstituted pr...
Scheme 73: C(sp2)–H arylation of arenes catalyzed by dual NHC–Cu/NHC–Pd catalytic system.
Scheme 74: C(sp2)–H Amidation of (hetero)arenes with N-chlorocarbamates/N-chloro-N-sodiocarbamates catalyzed b...
Scheme 75: NHC–CuI catalyzed thiolation of benzothiazoles and benzoxazoles.
Synthesis of ether lipids: natural compounds and analogues
- Marco Antônio G. B. Gomes,
- Alicia Bauduin,
- Chloé Le Roux,
- Romain Fouinneteau,
- Wilfried Berthe,
- Mathieu Berchel,
- Hélène Couthon and
- Paul-Alain Jaffrès
Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96
Graphical Abstract
Figure 1: Chemical structure of some natural ether lipids (ELs).
Figure 2: Synthesis of lyso-PAF and PAF from 1-O-alkylglycerol [64].
Figure 3: Synthesis of lyso-PAF from 1,3-benzylideneglycerol 3.1 [69].
Figure 4: A) Synthesis of the two enantiomers of octadecylglycerol (4.6 and 4.10) from ᴅ-mannitol (4.1); B) s...
Figure 5: Four-step synthesis of PAF 5.6 from (S)-glycidol [73].
Figure 6: Synthesis of 1-O-alkylglycerol A) from solketal, B) from ᴅ- or ʟ-tartaric acid and the intermediate ...
Figure 7: Synthesis of EL building blocks starting from substituted glycidol 7.1a–c [82].
Figure 8: Synthesis of PAF 8.5 by using phosphoramidite 8.2 [86].
Figure 9: Synthesis of oleyl-PAF 9.7 from ʟ-serine [88].
Figure 10: Synthesis of racemic analogues of lyso-PAF 10.8 and PAF 10.9 featuring a phenyl group between the g...
Figure 11: Synthesis of racemic deoxy-lyso-PAF 11.7 and deoxy-PAF 11.8 [91].
Figure 12: Synthesis of racemic thio-PAF 12.8 [93].
Figure 13: Racemic synthesis of 13.6 to illustrate the modification of the glycerol backbone by adding a methy...
Figure 14: Racemic synthesis of 14.5 as an illustration of the introduction of methyl substituents on the glyc...
Figure 15: Synthesis of functionalized sn-2-acyl chains of PC-EL; A) Steglich esterification or acylation reac...
Figure 16: Synthesis of racemic mc-PAF (16.3), a carbamate analogue of PAF [102].
Figure 17: A) Synthesis of (R)-17.2 and (S)-17.6 starting from (S)-solketal (17.1); B) synthesis of N3-PAF (17...
Figure 18: Modification of the phosphocholine polar head to produce PAF analogues [81].
Figure 19: Racemic PAF analogues 19.3 and 19.5 characterized by the absence of the phosphate group [107].
Figure 20: Synthesis of PIP3-PAF (20.7) [108].
Figure 21: Large-scale synthesis of C18-edelfosine (21.8) [116].
Figure 22: Synthesis of C16-edelfosine (22.10) starting from isopropylidene-ʟ-glyceric acid methyl ester (22.1...
Figure 23: Phosphocholine moiety installation by the use of chlorophosphite 23.2 as key reagent [119].
Figure 24: Synthesis of rac-1-alkyl-2-O-methylglycerol (AMG) [120].
Figure 25: Synthesis of stereocontrolled 1-alkyl-2-O-methyl glycerol 25.9 (AMG) from dimethyl ᴅ-tartrate [81].
Figure 26: A) Racemic synthesis of thioether 26.4 [129,130], B) structure of sulfone analogue 26.5 [129].
Figure 27: Stereocontrolled synthesis of C18-edelfosine thioether analogue 27.8 [118].
Figure 28: Synthesis of thioether 28.4 that include a thiophosphate function [134].
Figure 29: Synthesis of ammonium thioether 29.4 and 29.6 [135].
Figure 30: Synthesis of the N-methylamino analogue of edelfosine 30.6 (BN52211) [138].
Figure 31: Synthesis of 1-desoxy analogues of edelfosine; A) with a saturated alkyl chain; B) synthesis of the...
Figure 32: Stereocontrolled synthesis of edelfosine analogue (S)-32.8 featuring a C18:1 lipid chain [142].
Figure 33: Synthesis of edelfosine analogues with modulation of the lipid chain; A) illustration with the synt...
Figure 34: Synthesis of phospholipid featuring a carbamate function to link the lipid chain to the glycerol un...
Figure 35: Synthesis of sesquiterpene conjugates of phospho glycero ether lipids [148].
Figure 36: Racemic synthesis of methyl-substituted glycerol analogues 36.7 and 36.10: A) synthesis of diether ...
Figure 37: Racemic synthesis of ilmofosine (37.6) [155,156].
Figure 38: A) Stereoselective synthesis of 38.5 via a stereoselective hydroboration reaction; B) synthesis of ...
Figure 39: Racemic synthesis of SRI62-834 (39.6) featuring a spiro-tetrahydrofurane heterocycle in position 2 ...
Figure 40: Racemic synthesis of edelfosine analogue 40.5 featuring an imidazole moiety in sn-2 position [160].
Figure 41: Racemic synthesis of fluorine-functionalized EL: A) Synthesis of 41.6 and B) synthesis of 41.8 [161-163].
Figure 42: A) Synthesis of the β-keto-ester 42.6 that also features a decyl linker between the phosphate and t...
Figure 43: Synthesis of phosphonate-based ether lipids; A) edelfosine phosphonate analogue 43.7 and B) thioeth...
Figure 44: Enantioselective synthesis of phosphonates 44.3 and 44.4 [171].
Figure 45: Racemic synthesis of phosphinate-based ether lipid 45.10 [172].
Figure 46: Racemic synthesis of edelfosine arsonium analogue 46.5 [173].
Figure 47: Synthesis of edelfosine dimethylammonium analogue 47.2 [118].
Figure 48: Synthesis of rac-C18-edelfosine methylammonium analogue 48.4 [176].
Figure 49: A) Synthesis of edelfosine N-methylpyrrolidinium analogue 49.2 or N-methylmorpholinium analogue 49.3...
Figure 50: A) Synthesis of edelfosine’s analogue 50.4 with a PE polar group; B) illustration of a pyridinium d...
Figure 51: A) Synthesis of 51.4 featuring a thiazolium cationic moiety; B) synthesis of thiazolium-based EL 51...
Figure 52: Synthesis of cationic ether lipids 52.3, 52.4 and 52.6 [135,183].
Figure 53: Synthesis of cationic carbamate ether lipid 53.5 [184].
Figure 54: Synthesis of cationic sulfonamide 54.5 [185].
Figure 55: Chemical structure of ONO-6240 (55.1) and SRI-63-119 (55.2).
Figure 56: Synthesis of non-ionic ether lipids 56.2–56.9 [188].
Figure 57: Synthesis of ether lipid conjugated to foscarnet 57.6 [189].
Figure 58: A) Synthesis of ether lipid conjugated to arabinofuranosylcytosine; B) synthesis of AZT conjugated ...
Figure 59: Synthesis of quercetin conjugate to edelfosine [191].
Figure 60: Synthesis of 60.8 (Glc-PAF) [194].
Figure 61: A) Synthesis of amino ether lipid 61.7 functionalized with a rhamnose unit and its amide analogue 6...
Figure 62: A) Synthesis of glucose ether lipid 62.4; B) structure of ether lipid 62.5 possessing a maltose uni...
Figure 63: A) Synthesis of glucuronic methyl ester 63.8; B) structure of cellobiose 63.9 and maltose 63.10 ana...
Figure 64: A) Synthesis of maltosyl glycerolipid 64.7; B) structure of lactose analogue 64.8 prepared followin...
Figure 65: A) Asymmetric synthesis of the aglycone moiety starting from allyl 4-methoxyphenyl ether; B) glycos...
Figure 66: A) Synthesis of ohmline possessing a lactose moiety. B) Structure of other glyco glycero lipids pre...
Figure 67: A) Synthesis of lactose-glycerol ether lipid 67.5; B) analogues possessing a maltose (67.6) or meli...
Figure 68: Synthesis of digalactosyl EL 68.6, A) by using trityl, benzyl and acetyl protecting groups, B) by u...
Figure 69: A) Synthesis of α-ohmline; B) structure of disaccharide ether lipids prepared by using similar meth...
Figure 70: Synthesis of lactose ether lipid 70.3 and its analogue 70.6 featuring a carbamate function as linke...
Figure 71: Synthesis of rhamnopyranoside diether 71.4 [196].
Figure 72: Synthesis of 1-O-hexadecyl-2-O-methyl-3-S-(α-ᴅ-1'-thioglucopyranosyl)-sn-glycerol (72.5) [225].
Figure 73: A) Preparation of lipid intermediate 73.4; B) synthesis of 2-desoxy-C-glycoside 73.10 [226].
Figure 74: Synthesis of galactose-pyridinium salt 74.3 [228].
Figure 75: Synthesis of myo-inositol derivative Ino-C2-PAF (75.10) [230].
Figure 76: A) Synthesis of myo-inositol phosphate building block 76.7; B) synthesis of myo-inositolphosphate d...
Figure 77: A) Synthesis of phosphatidyl-3-desoxy-inositol 77.4; B) synthesis of phosphono-3-desoxyinositol 77.9...
Figure 78: A) Structure of diether phosphatidyl-myo-inositol-3,4-diphosphate 78.1; B) synthesis of phosphatidy...
Figure 79: A) Synthesis of diether-phosphatidyl derivative 79.4 featuring a hydroxymethyl group in place of a ...
Figure 80: Synthesis of Glc-amine-PAF [78].
Figure 81: Synthesis of glucosamine ether lipid 81.4 and its analogues functionalized in position 3 of the ami...
Figure 82: Synthesis of fully deprotected aminoglucoside ether lipid 82.5 [246].
Figure 83: Synthesis of C-aminoglycoside 83.12 using Ramberg–Bäcklund rearrangement as a key step [250].
Figure 84: A) List of the most important glyco lipids and amino glyco lipids included in the study of Arthur a...
Figure 85: Synthesis of mannosamine ether lipid 85.6 [254].
Figure 86: A) Synthesis of glucosamine ether lipids with a non-natural ʟ-glucosamine moiety; B) synthesis of e...
Figure 87: A) Structure of the most efficient anticancer agents 87.1–87.4 featuring a diamino glyco ether lipi...
Figure 88: A) Synthesis of diamino glyco ether lipid 87.4; B) synthesis of bis-glycosylated ether lipid 88.10 [256]....
Figure 89: Synthesis of triamino ether lipid 89.4 [260].
Figure 90: Synthesis of chlorambucil conjugate 90.7 [261].
Figure 91: Three main methods for the preparation of glycerol ether lipid 91.3; A) from solketal and via a tri...
Figure 92: Four different methods for the installation of the phosphocholine polar head group; A) method using...
Figure 93: Illustration of two methods for the installation of saccharides or aminosaccharides; A) O-glycosyla...
Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach
- Dileep Kumar Singh and
- Rajesh Kumar
Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71
- synthesis of N-substituted pyrroles 29 in the yields of 85–97% using squaric acid as catalyst. In this reaction, various amines 28 and 2,5-DMTHF (2) were reacted in greener solvents like water, deep eutectic solvent (DEC) and polyethylene glycol (PEG) under thermal or ultrasonic irradiation (Scheme 13a
Graphical Abstract
Figure 1: Various pyrrole containing molecules.
Scheme 1: Various synthestic protocols for the synthesis of pyrroles.
Figure 2: A tree-diagram showing various conventional and green protocols for Clauson-Kaas pyrrole synthesis.
Scheme 2: A general reaction of Clauson–Kaas pyrrole synthesis and proposed mechanism.
Scheme 3: AcOH-catalyzed synthesis of pyrroles 5 and 7.
Scheme 4: Synthesis of N-substituted pyrroles 9.
Scheme 5: P2O5-catalyzed synthesis of N-substituted pyrroles 11.
Scheme 6: p-Chloropyridine hydrochloride-catalyzed synthesis of pyrroles 13.
Scheme 7: TfOH-catalyzed synthesis of N-sulfonylpyrroles 15, N-sulfonylindole 16, N-sulfonylcarbazole 17.
Scheme 8: Scandium triflate-catalyzed synthesis of N-substituted pyrroles 19.
Scheme 9: MgI2 etherate-catalyzed synthesis and proposed mechanism of N-arylpyrrole derivatives 21.
Scheme 10: Nicotinamide catalyzed synthesis of pyrroles 23.
Scheme 11: ZrOCl2∙8H2O catalyzed synthesis and proposed mechanism of pyrrole derivatives 25.
Scheme 12: AcONa catalyzed synthesis of N-substituted pyrroles 27.
Scheme 13: Squaric acid-catalyzed synthesis and proposed mechanism of N-substituted pyrroles 29.
Figure 3: Reusability of catalyst γ-Fe2O3@SiO2-Sb-IL in six cycles.
Scheme 14: Magnetic nanoparticle-supported antimony catalyst used in the synthesis of N-substituted pyrroles 31...
Scheme 15: Iron(III) chloride-catalyzed synthesis of N-substituted pyrroles 33.
Scheme 16: Copper-catalyzed Clauson–Kaas synthesis and mechanism of pyrroles 35.
Scheme 17: β-CD-SO3H-catalyzed synthesis and proposed mechanism of pyrroles 37.
Figure 4: Recyclability of β-cyclodextrin-SO3H.
Scheme 18: Solvent-free and catalyst-free synthesis and plausible mechanism of N-substituted pyrroles 39.
Scheme 19: Nano-sulfated TiO2-catalyzed synthesis of N-substituted pyrroles 41.
Figure 5: Plausible mechanism for the formation of N-substituted pyrroles catalyzed by nano-sulfated TiO2 cat...
Scheme 20: Copper nitrate-catalyzed Clauson–Kaas synthesis and mechanism of N-substituted pyrroles 43.
Scheme 21: Synthesis of N-substituted pyrroles 45 by using Co catalyst Co/NGr-C@SiO2-L.
Scheme 22: Zinc-catalyzed synthesis of N-arylpyrroles 47.
Scheme 23: Silica sulfuric acid-catalyzed synthesis of pyrrole derivatives 49.
Scheme 24: Bismuth nitrate-catalyzed synthesis of pyrroles 51.
Scheme 25: L-(+)-tartaric acid-choline chloride-catalyzed Clauson–Kaas synthesis and plausible mechanism of py...
Scheme 26: Microwave-assisted synthesis of N-substituted pyrroles 55 in AcOH or water.
Scheme 27: Synthesis of pyrrole derivatives 57 using a nano-organocatalyst.
Figure 6: Nano-ferric supported glutathione organocatalyst.
Scheme 28: Microwave-assisted synthesis of N-substituted pyrroles 59 in water.
Scheme 29: Iodine-catalyzed synthesis and proposed mechanism of pyrroles 61.
Scheme 30: H3PW12O40/SiO2-catalyzed synthesis of N-substituted pyrroles 63.
Scheme 31: Fe3O4@-γ-Fe2O3-SO3H-catalyzed synthesis of pyrroles 65.
Scheme 32: Mn(NO3)2·4H2O-catalyzed synthesis and proposed mechanism of pyrroles 67.
Scheme 33: p-TsOH∙H2O-catalyzed (method 1) and MW-assisted (method 2) synthesis of N-sulfonylpyrroles 69.
Scheme 34: ([hmim][HSO4]-catalyzed Clauson–Kaas synthesis of pyrroles 71.
Scheme 35: Synthesis of N-substituted pyrroles 73 using K-10 montmorillonite catalyst.
Scheme 36: CeCl3∙7H2O-catalyzed Clauson–Kaas synthesis of pyrroles 75.
Scheme 37: Synthesis of N-substituted pyrroles 77 using Bi(NO3)3∙5H2O.
Scheme 38: Oxone-catalyzed synthesis and proposed mechanism of N-substituted pyrroles 79.
Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities
- Jorge de Lima Neto and
- Paulo Henrique Menezes
Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31
- . Subsequent one-step reaction using sodium borohydride and polyethylene glycol gave directly alcohol 124, which was subjected to the Mitsunobu reaction with the carboxylic acid 112. The obtained ester 125 was then used in an intramolecular Ullmann reaction to yield the benzylated combretastatin D-4, 109 in
Graphical Abstract
Figure 1: Structures of some members of the combretastatin D series, corniculatolides, and isocorniculatolide...
Scheme 1: Biosynthetic pathway proposed by Pettit and co-workers.
Scheme 2: Biosynthetic pathway towards corniculatolides or isocorniculatolides proposed by Ponnapalli and co-...
Scheme 3: Retrosynthetic approaches.
Scheme 4: Attempt of total synthesis of 2 by Boger and co-workers employing the Mitsunobu approach [27].
Scheme 5: Total synthesis of combretastatin D-2 (2) reported by Boger and co-workers employing an intramolecu...
Scheme 6: Formal synthesis of combretastatin D-2 (2) by Deshpande and co-workers using the Mitsunobu conditio...
Scheme 7: Total synthesis of combretastatin D-2 (2) by Rychnovsky and Hwang [36].
Scheme 8: Divergent synthesis of (±)-1 form combretastatin D-2 (2) by Rychnovsky and Hwang [36].
Scheme 9: Enantioselective synthesis of 1 by Rychnovsky and Hwang employing Jacobsen catalyst [41].
Scheme 10: Synthesis of fragment 57 by Couladouros and co-workers [43,45].
Scheme 11: Formal synthesis of compound 2 by Couladouros and co-workers [43,45].
Scheme 12: Synthesis of fragment 66 by Couladouros and co-workers [44,45].
Scheme 13: Synthesis of fragment 70 by Couladouros and co-workers [44,45].
Scheme 14: Synthesis of fragment 77 by Couladouros and co-workers [44,45].
Scheme 15: Synthesis of combretastatins 1 and 2 by Couladouros and co-workers [44,45].
Scheme 16: Formal synthesis of compound 2 by Gangakhedkar and co-workers [48].
Scheme 17: Synthesis of fragment 14 by Cousin and co-workers [50].
Scheme 18: Synthesis of fragment 91 by Cousin and co-workers [50].
Scheme 19: Formal synthesis of compound 2 by Cousin and co-workers [50].
Scheme 20: Synthesis of 2 diolide by Cousin and co-workers [50].
Scheme 21: Synthesis of combretastatin D-4 (4) by Nishiyama and co-workers [54].
Scheme 22: Synthesis of fragment 112 by Pettit and co-workers [55].
Scheme 23: Synthesis of fragment 114 by Pettit and co-workers [55].
Scheme 24: Attempt to the synthesis of compound 2 by Pettit and co-workers [55].
Scheme 25: Synthesis of combretastatin-D2 (2) starting from isovanilin (80) by Pettit and co-workers [55].
Scheme 26: Attempted synthesis of combretastatin-D2 (2) derivatives through an SNAr approach [55].
Scheme 27: Synthesis of combretastatin D-4 (4) by Pettit and co-workers [55].
Scheme 28: Synthesis of combretastatin D-2 (2) by Harras and co-workers [57].
Scheme 29: Synthesis of combretastatin D-4 (4) by Harras and co-workers [57].
Scheme 30: Formal synthesis of combretastatin D-1 (1) by Harras and co-workers [57].
Scheme 31: Synthesis of 11-O-methylcorniculatolide A (5) by Raut and co-workers [69].
Scheme 32: Synthesis of isocorniculatolide A (7) and O-methylated isocorniculatolide A 8 by Raut and co-worker...
Scheme 33: Synthesis of isocorniculatolide B (10) and hydroxyisocorniculatolide B 175 by Kim and co-workers [71].
Scheme 34: Synthesis of compound 9, 178, and 11 by Kim and co-workers [71].
Scheme 35: Synthesis of combretastatin D-2 prodrug salts [55].
Figure 2: ED50 values of the combretastatin D family against murine P388 lymphocytic leukemia cell line (appr...
Figure 3: IC50 of compounds against α-glucosidase [19].
Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis
- Nicoleta G. Hădărugă,
- Gabriela Popescu,
- Dina Gligor (Pane),
- Cristina L. Mitroi,
- Sorin M. Stanciu and
- Daniel Ioan Hădărugă
Beilstein J. Org. Chem. 2023, 19, 380–398, doi:10.3762/bjoc.19.30
- -based ternary complexes, but they do not deal with triglyceride-based vegetable oils or with flavonoid glycosides/flavonolignans. Most of these studies are related to controlled release of various drugs from the CD complexes such as diosmin and polyethylene glycol, haloperidol and lactic acid
Graphical Abstract
Figure 1: Hypothetical interactions between the β-cyclodextrin host and guest molecules (flavonoid glycoside/...
Figure 2: Superposition of the FTIR spectra for the β-cyclodextrin/Corylus avellana oil/hesperidin ternary co...
Figure 3: Superposition of the FTIR spectra for the β-cyclodextrin/Corylus avellana oil/hesperidin ternary co...
Figure 4: PC2 versus PC1 scores plot from the FTIR–PCA analysis of the flavonoid glycoside and flavonolignan ...
Figure 5: PC2 versus PC1 scores plot from the FTIR–PCA analysis of the β-CD/hazelnut oil/flavonoid ternary co...
Figure 6: PC2 versus PC1 scores plot from the FTIR–PCA analysis of the β-CD/hazelnut oil/flavonoid ternary co...
Figure 7: PC2 versus PC1 scores plot from the FTIR–PCA analysis of the β-CD/hazelnut oil/flavonoid ternary co...
Figure 8: PC3 versus PC1 scores plot from the FTIR-PCA analysis of the β-CD/hazelnut oil/flavonoid ternary co...
Figure 9: PC3 versus PC2 scores plot from the FTIR–PCA analysis of the β-CD/hazelnut oil/flavonoid ternary co...
Figure 10: PC2 versus PC1 loadings plot from the FTIR–PCA analysis of the β-CD/hazelnut oil/flavonoid ternary ...
Figure 11: PC3 versus PC1 loadings plot from the FTIR–PCA analysis of the β-CD/hazelnut oil/flavonoid ternary ...
Figure 12: Eigenvalues of the correlation matrix from the FTIR–PCA analysis of the β-CD/hazelnut oil/flavonoid...
Investigation of cationic ring-opening polymerization of 2-oxazolines in the “green” solvent dihydrolevoglucosenone
- Solomiia Borova and
- Robert Luxenhofer
Beilstein J. Org. Chem. 2023, 19, 217–230, doi:10.3762/bjoc.19.21
- biomedical applications, in particular as an alternative to the hydrophilic poly(ethylene glycol) (PEG), which is the polymer of choice for many biomedical applications due to its high solubility, low cytotoxicity and biocompatibility [3][4][5][6][7][8][9]. However, an ongoing discussion about pre-existing
Graphical Abstract
Figure 1: Schematic representation of the mechanism of the cationic ring-opening polymerization (CROP) of 2-a...
Figure 2: (a) First-order kinetic plot for the 2-ethyl-2-oxazoline ring-opening polymerization in DLG at 90 °...
Figure 3: MALDI-TOF mass spectrometry analysis of the poly(2-ethyl-2-oxazoline) initiated with methyl triflat...
Figure 4: MALDI-TOF mass spectrometry analysis of the poly(2-ethyl-2-oxazoline) initiated with 2-ethyl-3-meth...
Figure 5: Schematic illustration of the side reactions that can occur during the polymerization of 2-alkyl-2-...
Figure 6: Investigation of 2-ethyl-2-oxazoline polymerization in DLG at 60 °C initiated with MeOTf (black), M...
Figure 7: Investigation of 2-ethyl-2-oxazoline polymerization initiated with EtOxMeOTf at different monomer/i...
Automated grindstone chemistry: a simple and facile way for PEG-assisted stoichiometry-controlled halogenation of phenols and anilines using N-halosuccinimides
- Dharmendra Das,
- Akhil A. Bhosle,
- Amrita Chatterjee and
- Mainak Banerjee
Beilstein J. Org. Chem. 2022, 18, 999–1008, doi:10.3762/bjoc.18.100
- relatively inferior results than EtOH (Table 1, entry 3). The use of ethylene glycol and glycerol as the grinding matrix showed improved yields with the monobromo product 2a formed in 81% and 85% yield, respectively within 10 min (Table 1, entries 4 and 5). Next, liquid polyethylene glycol, PEG-400 was
Graphical Abstract
Figure 1: Representative examples of important halogen-containing aryl derivatives.
Scheme 1: Strategies for halogenation of aromatic compounds using NXS.
Scheme 2: General scheme of PEG-400-assisted halogenation of phenols and anilines in an automated grinder usi...
Scheme 3: Monohalogenation of phenols and anilines by automated grinding with NXS. All yields refer to the is...
Scheme 4: Dihalogenation of phenols and anilines with NXS by automated grinding. All yields refer to the isol...
Scheme 5: Gram-scale monobromination of p-cresol by NBS in the automated grinder.
Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides
- Md Imran Hossain,
- Md Imdadul H. Khan,
- Seong Jong Kim and
- Hoang V. Le
Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47
- , Saugus, MA, USA). The DART ion source was operated with helium gas (approximately 4.0 L/min flow rate), the gas heater (350 °C), and the source grid (350 V). The data acquisition range was from m/z 50 to 1000. Polyethylene glycol (PEG 600) was used for the exact mass calibration. General synthetic
Graphical Abstract
Figure 1: Routes to isoxazoles.
Figure 2: Possible products of the reaction between nitrile oxides and 1,3-diketones. Path D (C-trapping) pro...
Figure 3: Reactions between various arylhydroximoyl chlorides and 1,3-diketones. The reactions were performed...
Figure 4: Reactions between various phenyl hydroximoyl chlorides and β-ketoesters or β-ketoamides. The reacti...
Figure 5: Reactions between 4-fluorophenyl hydroximoyl chloride (1a) and diethyl malonate (2j) or dibenzyl ma...
Figure 6: Reactions between phenyl hydroximoyl chlorides 1a,c and 4,4,4-trifluoro-1-phenyl- (2l) and 4,4,4-tr...
Figure 7: 1H NMR spectra of 1-phenyl-1,3-butanedione (2a) in methanol-d4 (top) and in CDCl3 (bottom).
Figure 8: A plausible mechanism for the formation of the 3,4,5-trisubstituted isoxazoles 3 in the presence of...
Figure 9: Structures of β-lactamase-resistant antibiotics oxacillin, cloxacillin, dicloxacillin, and flucloxa...
Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions
- Surendran Amrutha,
- Sankaran Radhika and
- Gopinathan Anilkumar
Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31
- catalytic efficiency than other catalytic systems. For studying the efficiency of the catalyst, they selected the reaction of 4-iodonitrobenzene and phenylacetylene in the presence of 0.5 mol % of Fe2O3 nanoparticle as catalyst and K2CO3 as base in ethylene glycol at 80 °C. Both, the electrophilic character
- latter with salts of Pd(II) and Co(II) in ethylene glycol and water at pH 11 afforded the desired PdCo nanoparticles-3D graphene nanocomposite. The catalyst was then studied in the Sonogashira coupling reaction of arylacetylenes and aryl halides in the presence of various bases and solvents. The maximum
- compatible with the catalyst and afforded the products with high yield. The efficiency of the catalyst in water was found to be increased by introducing polyethylene glycol (PEG) chains. From the mechanistic explanation, the reaction proceeds via an oxidative addition and reductive elimination route. Fe3O4
Graphical Abstract
Scheme 1: One pot Sonogashira coupling of aryl iodides with arylynols in the presence of iron(III) chloride h...
Scheme 2: The iron-catalyzed Sonogashira coupling of aryl iodides with terminal acetylenes in water under aer...
Scheme 3: Sonogashira coupling of aryl halides and phenylacetylene in the presence of iron nanoparticles.
Scheme 4: Sonogashira coupling catalyzed by a silica-supported heterogeneous Fe(III) catalyst.
Scheme 5: Suggested catalytic cycle for the Sonogashira coupling using a silica-supported heterogeneous Fe(II...
Scheme 6: Chemoselective iron-catalyzed cross coupling of 4-bromo-1-cyclohexen-1-yltrifluromethane sulfonate ...
Scheme 7: Fe-catalyzed Sonogashira coupling between terminal alkynes and aryl iodides.
Scheme 8: Iron-catalyzed domino Sonogashira coupling and hydroalkoxylation.
Scheme 9: Sonogashira coupling of aryl halides and phenylacetylene in the presence of Fe(III) acetylacetonate...
Scheme 10: Sonogashira coupling of aryl iodides and alkynes with Fe(acac)3/2,2-bipyridine catalyst.
Scheme 11: Sonogashira cross-coupling of terminal alkynes with aryl iodides in the presence of Fe powder/ PPh3...
Scheme 12: α-Fe2O3 nanoparticles-catalyzed coupling of phenylacetylene with aryl iodides.
Scheme 13: Sonogashira cross-coupling reaction between phenylacetylene and 4-substituted iodobenzenes catalyze...
Scheme 14: One-pot synthesis of 2-arylbenzo[b]furans via tandem Sonogashira coupling–cyclization protocol.
Scheme 15: Suggested mechanism of the Fe(III) catalyzed coupling of o-iodophenol with acetylene derivatives.
Scheme 16: Fe3O4@SiO2/Schiff base/Fe(II)-catalyzed Sonogashira–Hagihara coupling reaction.
Scheme 17: Sonogashira coupling using the Fe(II)(bdmd) catalyst in DMF/1,4-dioxane.
Scheme 18: Synthesis of 7-azaindoles using Fe(acac)3 as catalyst.
Scheme 19: Plausible mechanistic pathway for the synthesis of 7-azaindoles.
Scheme 20: Synthesis of Co@imine-POP catalyst.
Scheme 21: Sonogashira coupling of various arylhalides and phenylacetylene in the presence of Co@imine-POP cat...
Scheme 22: Sonogashira coupling of aryl halides and phenylacetylene using Co-DMM@MNPs/chitosan.
Scheme 23: Sonogashira cross-coupling of aryl halides with terminal acetylenes in the presence of Co-NHC@MWCNT...
Scheme 24: Sonogashira cross-coupling of aryl halides with terminal acetylenes in the presence of Co nanoparti...
Scheme 25: Sonogashira coupling reaction of aryl halides with phenylacetylene in the presence of Co nanopartic...
Scheme 26: PdCoNPs-3DG nanocomposite-catalyzed Sonogashira cross coupling of aryl halide and terminal alkynes.
Scheme 27: Sonogashira cross-coupling of aryl halides and phenylacetylene in the presence of graphene-supporte...
Scheme 28: Sonogashira cross-coupling with Pd/Co ANP-PPI-graphene.
Scheme 29: Pd-Co-1(H)-catalyzed Sonogashira coupling reaction.
Scheme 30: The coupling of aryl halides with terminal alkynes using cobalt hollow nanospheres as catalyst.
Scheme 31: A plausible mechanism for the cobalt-catalyzed Sonogashira coupling reaction.
Scheme 32: Sonogashira cross-coupling reaction of arylhalides with phenylacetylene catalyzed by Fe3O4@PEG/Cu-C...
Scheme 33: Plausible mechanism of Sonogashira cross-coupling reaction catalyzed by Fe3O4@PEG/Cu-Co.
Scheme 34: Sonogashira coupling reaction of para-substituted bromobenzenes with phenylacetylene in the presenc...
Scheme 35: Possible mechanism for the visible light-assisted cobalt complex-catalyzed Sonogashira coupling. (R...
Scheme 36: Sonogashira cross-coupling of aryl halides and phenylacetylene using cobalt as additive.
Scheme 37: Plausible mechanism of Sonogashira cross-coupling reaction over [LaPd*]. (Reproduced with permissio...
1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis
- Ruan Carlos B. Ribeiro,
- Patricia G. Ferreira,
- Amanda de A. Borges,
- Luana da S. M. Forezi,
- Fernando de Carvalho da Silva and
- Vitor F. Ferreira
Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5
- °C, and method B was carried out with t-BuOK in polyethylene glycol (PEG300) at room temperature. In both methods, the reaction conditions were mild and produced the product in moderate to good yields. The same group investigated this reaction with substituted acetonitriles to obtain 2
Graphical Abstract
Figure 1: Naphthoquinones are commonly used in organic synthesis.
Figure 2: Some important natural and synthetic naphthoquinones.
Scheme 1: Synthetic studies of BNQs and reactions with amines.
Scheme 2: Methods described for the synthesis of β-NQS.
Figure 3: Drugs detected using β-NQSNa.
Scheme 3: Reactions between β-NQS and amines.
Scheme 4: Isomerization of 4-arylamino-1,2-naphthoquinones.
Scheme 5: Synthesis of unsymmetrical 2-amino-4-imino compounds.
Scheme 6: Synthesis of bis(isoxazolyl)naphthoquinones from β-NQS.
Scheme 7: The reaction of β-NQS with 30 followed by cycle condensation.
Scheme 8: Synthesis of 4-(2-amino-5-selenothiazoles)-1,2-naphthoquinones.
Scheme 9: Synthesis of amino- and phenoxy-1,2-naphthoquinones.
Scheme 10: Synthesis of 4-semicarbazide-1,2-naphthoquinone.
Scheme 11: Reactions of 4-azido-1,2-naphthoquinone.
Figure 4: Modifications that can be easily carried out from the products of β-NQS 8.
Scheme 12: Derivatives of 1,2-naphthoquinones obtained from β-NQS.
Scheme 13: Oximes as well as 4-amino- and 4-phenoxy-1,2-naphthoquinone as potential anti-inflammatory agents.
Scheme 14: Synthesis of triazoles from β-NQS.
Scheme 15: Synthesis of naphtho[1,2-d]oxazoles from β-NQS.
Scheme 16: A) Arylation and vinylation of β-NQS catalyzed by Ni(II) salts. B) Transformation of the 1,2-dicarb...
Scheme 17: Benzo[a]carbazole and benzo[c]carbazoles fused with 1,2-naphthoquinone.
Scheme 18: Synthesis of 1,2-naphthoquinones having a C=C bond from β-NQS. Method A: NaOH, EtOH/H2O, 40 °C, 2 h...
Scheme 19: C=C bond formation from β-NQS and substituted acetonitriles.
Stepwise PEG synthesis featuring deprotection and coupling in one pot
- Logan Mikesell,
- Dhananjani N. A. M. Eriyagama,
- Yipeng Yin,
- Bao-Yuan Lu and
- Shiyue Fang
Beilstein J. Org. Chem. 2021, 17, 2976–2982, doi:10.3762/bjoc.17.207
- method is expected to significantly lower PEG synthesis cost. Keywords: base-labile; monodisperse; PEG; polyethylene glycol; protecting group; Introduction Polyethylene glycols and derivatives (PEGs) have found wide applications in many areas [1][2][3][4][5][6]. For some applications, polydisperse PEGs
Graphical Abstract
Scheme 1: A comparison of the new PEG synthesis method with a typical known PEG synthesis method.
Scheme 2: Screening base-labile protecting groups for stepwise PEG synthesis. All compounds (3a–l) underwent ...
Scheme 3: Synthesis of monomer 2.
Scheme 4: PEG synthesis using the one-pot PEG elongation approach.
Scheme 5: A proposed route for the synthesis of long and asymmetric PEGs using a base-labile protecting group....
