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Search for "acetals" in Full Text gives 114 result(s) in Beilstein Journal of Organic Chemistry.
Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides
- Kartik Temburnikar and
- Katherine L. Seley-Radtke
Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65
- condensation of alkyl-substituted silyl ketene acetals (32) with enantioenriched α-2,2,6,6-tetramethylpiperidinyl-β-benzyloxypropionaldehyde (33) in presence of TiCl2(OiPr)2 to give the β-hydroxyester 34 that is diastereomerically enriched [75][95]. Reductive cleavage of the 2,2,6,6-tetramethylpiperidinyl (TMP
- ) group by Zn and trifloroacetic acid results in cyclization and formation of the C2'- substituted ribonolactone (35). TiCl2(OiPr)2 has been identified as the optimal Lewis acid for the synthesis of most ribonolactones with the exception of unsubstituted silyl ketene acetals (R = R' = H) that leads to
Graphical Abstract
Figure 1: Structural components of nucleic acids. Shown is the monomeric building block of nucleic acids. Cha...
Figure 2: Formation of oxocarbenium ion during glycosidic bond cleavage in nucleosides [31]. The extent of leavin...
Figure 3: Structural modifications to nucleobase-sugar connectivity. The O–C–N bond between nucleobase and su...
Figure 4: Examples of natural and synthetic C-nucleosides. Pseudouridine and formcycin are among several natu...
Figure 5: Synthetic approaches to C-nucleosides. A. Two common strategies for C-nucleoside synthesis involve ...
Figure 6: Steroselective C-nucleoside synthesis using D-ribonolactone. A. Nucleophilic substitution of D-ribo...
Figure 7: Synthesis of C1'-substituted 4-aza-7,9-dideazaadenine C-nucleosides [63-65,69,70]. A. Reaction of D-ribonolacton...
Figure 8: Pyrrolo- and imidazo[2,1-f][1,2,4]triazine C-nucleosides. A series of sugar- and nucleobase-substit...
Figure 9: Synthesis of 1',2'-cyclopentyl C-nucleoside [73]. Functional groups at C1' and C2' were installed and e...
Figure 10: Anti-influenza C-nucleosides mimicking favipiravir riboside [74]. A. Structure of favipiravir and its r...
Figure 11: Alternative method for synthesis of 2'-substituted C-nucleosides [75]. A. Synthesis of C2'-substituted ...
Figure 12: Synthesis of carbocyclic C-nucleosides using cyclopentanone [53]. A. Nucleophlic substitution on cyclop...
Figure 13: Synthesis of carbocyclic C-nucleosides via Suzuki coupling [53]. A. Synthesis of OTf-cyclopentene that ...
Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ6-sulfanyl)acetic acid esters with aldehydes
- Anna-Lena Dreier,
- Andrej V. Matsnev,
- Joseph S. Thrasher and
- Günter Haufe
Beilstein J. Org. Chem. 2018, 14, 373–380, doi:10.3762/bjoc.14.25
- organic synthesis applied most successfully for the construction of natural products and their analogs [1][2]. Later this type of reaction was extended to enolized carboxylic acid derivatives, particularly to silylated ketene acetals, as reaction partners for carbonyl active compounds [3][4][5]. Mild and
Graphical Abstract
Scheme 1: Silicon-mediated Mukaiyama-type aldol reaction of octyl 2-(pentafluoro-λ6-sulfanyl)acetate (1) with ...
Figure 1: Newman projections of the syn- and the anti-diastereomeric aldol addition products.
Scheme 2: Mechanism of the formation of aldol addition products.
Scheme 3: Formation of (E)-configured aldol condensation products.
Scheme 4: Anticipated mechanism of formation of aldol condensation products.
Scheme 5: Synthesis of SF5-substituted acetmorpholide 8.
Scheme 6: Intermediate formation of the (Z)-ketene aminal from morpholide 8 with TMSOTf/ Et3N and subsequent ...
One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates
- Jun Ki Kim,
- Hwan Jung Lim,
- Kyung Chae Jeong and
- Seong Jun Park
Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16
- facile preparation of thienyl heterocycles 8. The mechanism for this reaction is based on the formation of a sulfur ylide-like intermediate. It was clearly suggested by (i) the intramolecular cyclization of ketene N,S-acetals 7 to the corresponding thiophenes 8, (ii) 1H NMR studies of Meldrum’s acid
- -substituted aminothioacetals 9, and (iii) substitution studies of the methoxy group on Meldrum’s acid containing N,S-acetals 9b. Notably, in terms of structural effects on the reactivity and stability of sulfur ylide-like intermediates, 2-pyridyl substituted compound 7a exhibited superior properties over
- primarily been prepared by base-catalyzed intramolecular Dieckmann-, Thorpe–Ziegler, and aldol-type condensations of the corresponding ketene-N,S-acetals [57][58][59][60][61][62][63][64][65][66][67]. These methods are still need strong bases [60], high temperatures [62][64][65], and are generally low
Graphical Abstract
Figure 1: The selected examples of sulfur(IV) and sulfur(VI) ylides 1 [1], 2 [5-7], 3 [6,7,9], 4 [11,12], 5 [33,34], 6 [35-38].
Figure 2: Metal-free synthesis of thiophene-based heterocycles (A) [54,55], (B) [56].
Scheme 1: One-pot sequential synthesis of the trisubstituted 5-(pyridine-2-yl)thiophenes 8a. Substrate: amalo...
Figure 3: X-ray crystal structures of 8ad and 8an [68].
Figure 4: The proposed structure of sulfur ylide-like intermediates; resonance contributors (mesomeric struct...
Scheme 2: The substitution reaction with MeOH.
Preparation and isolation of isobenzofuran
- Morten K. Peters and
- Rainer Herges
Beilstein J. Org. Chem. 2017, 13, 2659–2662, doi:10.3762/bjoc.13.263
- ) and methylated to DMIBF (7) [8]. However, yields in our hands are quite low. It is known that benzyl ethers are prone to oxidative functionalization [20]. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has been used to selectively oxidize benzyl ethers to acetals in the presence of alcohols [21
Graphical Abstract
Scheme 1: Diels–Alder reaction of isobenzofuran and formation of a benzene ring in the cycloadduct.
Scheme 2: Different approaches for the synthesis of IBF (1).
Scheme 3: Reaction of in situ prepared IBF (1) with DMAD (9).
1,3-Dibromo-5,5-dimethylhydantoin as promoter for glycosylations using thioglycosides
- Fei-Fei Xu,
- Claney L. Pereira and
- Peter H. Seeberger
Beilstein J. Org. Chem. 2017, 13, 1994–1998, doi:10.3762/bjoc.13.195
- ]. In synthetic chemistry, DBDMH acts as a thiophilic activator in the conversion of dithioacetals to the corresponding O,O-acetals [28][29][30], as well as in the synthesis of heparin mimetics [31]. We considered DBDMH as a readily available alternative promoter for glycosylations involving
Graphical Abstract
Scheme 1: DBDMH as promotor for automated glycan assembly. Modules: a) acidic wash; b) glycosylation using DB...
Scheme 2: Hydrolysis of glycosyl selenide 17 with DBDMH.
Accessing simply-substituted 4-hydroxytetrahydroisoquinolines via Pomeranz–Fritsch–Bobbitt reaction with non-activated and moderately-activated systems
- Marco Mottinelli,
- Mathew P. Leese and
- Barry V. L. Potter
Beilstein J. Org. Chem. 2017, 13, 1871–1878, doi:10.3762/bjoc.13.182
- , compounds bearing a different number of methoxy groups were selected in order to understand the electronic constrains that might render indole formation competitive. Upon treatment with 70% HClO4, acetals 9a and 9o yielded the respective THIQs 10a and 10o. However, the highly-activated acetal 9p exclusively
Graphical Abstract
Figure 1: Non-steroidal templates from estradiol.
Scheme 1: Pomeranz–Fritsch and Pomeranz–Fritsch–Bobbitt reactions. Conditions: (a) conc. H2SO4; (b) benzene, ...
Scheme 2: Designed synthesis of THIQ. Conditions: (a) NaBH(OAc)3, CHCl3, rt; (b) 6 M HCl or 70% HClO4 (see Table 1),...
Scheme 3: Side reaction during the double alkylation of 7 and possible reaction mechanism for the formation o...
Scheme 4: Competition between the formation of 5- and 7-substituted THIQs. Conditions: (a) 6 M HCl, rt.
Scheme 5: Formation of the 4-hydroxy and 4-methoxy-THIQs. Conditions: (a) 6 M HCl or 70% HClO4, rt (see Table 3).
Scheme 6: Competition between the formation of THIQs 10a,o,p and indoles 16a,o,p. Conditions: (a) 70% HClO4, ...
Scheme 7: Competition between 6- and 7-membered ring formation. Conditions: (a) NaBH(OAc)3, CHCl3, rt; (b) 2,...
Scheme 8: Competition between ring formation para- or meta- to an activating group. Conditions: (a) NaBH(OAc)3...
Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds
- M. Fernanda N. N. Carvalho,
- Rudolf Herrmann and
- Gabriele Wagner
Beilstein J. Org. Chem. 2017, 13, 1230–1238, doi:10.3762/bjoc.13.122
- orthoformates at room temperature in the presence of an acid. Thus, 3,3-dimethoxycamphersulfonylimine 16 and 3,3-diethoxycamphersulfonylimine 16’ were prepared [18][39]. The subsequent reaction of these acetals with one equivalent of lithium phenylacetylide or 1-heptynyllithium under conditions described above
Graphical Abstract
Scheme 1: Synthesis of 3-oxo-camphorsulfonylimine (3) [13,15] and its bis-alkynyl derivatives 4 from camphor-10-sulf...
Scheme 2: Reactions of bis-alkynyl camphor derivative 4a with TiCl4 and with Br2, respectively.
Scheme 3: Reactions of bis-alkynylcamphor derivatives 4a–e with catalytic amounts of PtCl2(PhCN)2.
Scheme 4: Attempted selective synthesis of 3-alkynyl derivatives via sulfonylimine reduction of oxoimide 3.
Scheme 5: Selective synthesis of 2-alkynyl derivatives by protection of the 3-oxo group as an acetal.
Scheme 6: Selective synthesis of 2-alkynyl derivatives by protection of the 3-oxo group as an imine.
Scheme 7: Synthesis of the bis-alkynyl derivatives bearing different alkyne substituents and their platinum-c...
Scheme 8: Proposed mechanism of the platinum-catalysed cycloisomerisation.
New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation
- Pavel Nagorny and
- Zhankui Sun
Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283
- -workers reported the use of N-alkylated 3,5-di(carbomethoxy)pyridinium ions L13 to catalyze the reaction between 1-chloroisochroman and silyl ketene acetals (Scheme 10A). Catalyst L13 with R3 = C6F5 was found to be particularly active, and was found to efficiently form the product at 2 mol % loading
- bond donors. However, catalytic halogen scavenging with halogen bond donors is also possible if the products are not inhibiting the catalyst. One of such transformations explored by the Huber group is the addition of ketene silyl acetals to 1-chloroisochroman (Scheme 17) [85][87]. The chloride anion
- -workers [52]. (A) Alkylpyridinium catalysts L13-catalyzed reaction of 1-isochroman and silyl ketene acetals by Berkessel and co-workers. (B) Evidence of L13 C–H···X– hydrogen bonding in solid state [55]. Mixed N–H/C–H two hydrogen bond donors L14 and L15 as organocatalysts for ROP of lactide by Bibal and
Graphical Abstract
Figure 1: Electrophile Activation by Hydrogen Bond Donors [1-16].
Figure 2: Early examples of C–H hydrogen bonds and their recent use in supramolecular chemistry [18,19,32-34].
Scheme 1: Design of 1,2,3-triazole-based catalysts for trityl group transfer through chloride anion binding b...
Scheme 2: Examples of chiral triazole-based catalysts for anion activation designed by Mancheno and co-worker...
Scheme 3: Application of chiral triazole-based catalysts L3 and L4 for counterion activation of pyridinium, q...
Scheme 4: Ammonium salt anion binding via C–H hydrogen bonds in solid state [40-45,50,51].
Scheme 5: Early examples of ammonium salts being used for electrophilic activation of imines in aza-Diels–Ald...
Scheme 6: Ammonium salts as hydrogen bond-donor catalysts by Bibal and co-workers [53,54].
Scheme 7: Tetraalkylammonium catalyst (L6)-catalyzed dearomatization of isoquinolinium salts [50].
Scheme 8: Tetraalkylammonium catalyst L6 complexation to halogen-containing substrates [51].
Scheme 9: Tetraalkylammonium-catalyzed aza-Diels–Alder reaction by Maruoka and co-workers [52].
Scheme 10: (A) Alkylpyridinium catalysts L13-catalyzed reaction of 1-isochroman and silyl ketene acetals by Be...
Scheme 11: Mixed N–H/C–H two hydrogen bond donors L14 and L15 as organocatalysts for ROP of lactide by Bibal a...
Scheme 12: Examples of stable complexes based on halogen bonding [68,69].
Scheme 13: Interaction between (−)-sparteine hydrobromide and (S)-1,2-dibromohexafluoropropane in the cocrysta...
Scheme 14: Iodine-catalyzed reactions that are computationally proposed to proceed through halogen bond to car...
Scheme 15: Transfer hydrogenation of phenylquinolines catalyzed by haloperfluoroalkanes by Bolm and co-workers ...
Scheme 16: Halogen bond activation of benzhydryl bromides by Huber and co-workers [82].
Scheme 17: Halogen bond-donor-catalyzed addition to oxocarbenium ions by Huber and co-workers [89].
Scheme 18: Halogen bond-donor activation of α,β-unsaturated carbonyl compounds in the [2 + 4] cycloaddition re...
Scheme 19: Halogen bond donor activation of imines in the [2 + 4] cycloaddition reaction of imine and Danishef...
Scheme 20: Transfer hydrogenation catalyzed by a chiral halogen bond donor by Tan and co-workers [91].
Scheme 21: Allylation of benzylic alcohols by Takemoto and co-workers [92].
Scheme 22: NIS induced semipinacol rearrangement via C–X bond cleavage [93].
Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations
- Serena Traboni,
- Emiliano Bedini and
- Alfonso Iadonisi
Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271
- stannylene acetals in the regioselective silylation of saccharide primary alcohols [37]. At this stage, it should be noted that pyridine is frequently employed as the solvent for silylations, but the conditions herein described can be referred to as “solvent-free” because of the very limited amount of
Graphical Abstract
Scheme 1: Multiple O-trimethylsilylations of saccharide compounds.
Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis
- Darcy J. Atkinson,
- Briar J. Naysmith,
- Daniel P. Furkert and
- Margaret A. Brimble
Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226
- aldol products 85 and 86 to acetals 87 and 88, respectively, was achieved using standard transformations and Goodman’s reagent (67) [67] was used to install the guanidine moiety. With both protected amino acids 87 and 88 in hand, the attention turned to the formation of tripeptide 78 (Scheme 17
Graphical Abstract
Figure 1: Structures of the enduracididine family of amino acids (1–6).
Figure 2: Enduracidin A (7) and B (8).
Figure 3: Minosaminomycin (9) and related antibiotic kasugamycin (10).
Figure 4: Enduracididine-containing compound 11 identified in a cytotoxic extract of Leptoclinides dubius [32].
Figure 5: Mannopeptimycins α–ε (12–16).
Figure 6: Regions of the mannopeptimycin structure investigated in structure–activity relationship investigat...
Figure 7: Teixobactin (17).
Scheme 1: Proposed biosynthesis of L-enduracididine (1) and L-β-hydroxyenduracididine (5).
Scheme 2: Synthesis of enduracididine (1) by Shiba et al.
Scheme 3: Synthesis of protected enduracididine diastereomers 31 and 32.
Scheme 4: Synthesis of the C-2 azido diastereomers 36 and 37.
Scheme 5: Synthesis of 2-azido-β-hydroxyenduracididine derivatives 38 and 39.
Scheme 6: Synthesis of protected β-hydroxyenduracididine derivatives 40 and 41.
Scheme 7: Synthesis of C-2 diastereomeric amino acids 46 and 47.
Scheme 8: Synthesis of protected β-hydroxyenduracididines 51 and 52.
Scheme 9: General transformation of alkenes to cyclic sulfonamide 54 via aziridine intermediate 53.
Scheme 10: Synthesis of (±)-enduracididine (1) and (±)-allo-enduracididine (3).
Scheme 11: Synthesis of L-allo-enduracididine (3).
Scheme 12: Synthesis of protected L-allo-enduracididine 63.
Scheme 13: Synthesis of β-hydroxyenduracididine derivative 69.
Scheme 14: Synthesis of minosaminomycin (9).
Scheme 15: Retrosynthetic analysis of mannopeptimycin aglycone (77).
Scheme 16: Synthesis of protected amino acids 87 and 88.
Scheme 17: Synthesis of mannopeptimycin aglycone (77).
Scheme 18: Synthesis of N-mannosylation model guanidine 92 and attempted synthesis of benzyl protected mannosy...
Scheme 19: Synthesis of benzyl protected mannosyl D-β-hydroxyenduracididine 97.
Scheme 20: Synthesis of L-β-hydroxyenduracididine 98.
Scheme 21: Total synthesis of mannopeptimycin α (12) and β (13).
Scheme 22: Synthesis of protected L-allo-enduracididine 102.
Scheme 23: The solid phase synthesis of teixobactin (17).
Scheme 24: Retrosynthesis of the macrocyclic core 109 of teixobactin (17).
Scheme 25: Synthesis of macrocycle 117.
Experimental and theoretical investigations into the stability of cyclic aminals
- Edgar Sawatzky,
- Antonios Drakopoulos,
- Martin Rölz,
- Christoph Sotriffer,
- Bernd Engels and
- Michael Decker
Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221
- their preparation and modification, it is remarkable that there is only little focus on the pH stability of these compounds in aqueous media. In general, the aminal moiety is known to undergo (similar to the corresponding O,O-acetals) acidic hydrolysis and can be considered as stable only within a
Graphical Abstract
Figure 1: Compounds described in the literature containing an aminal core for various applications. The amina...
Scheme 1: Synthetic approaches for the formation of the tetrahydroquinazoline moiety. Dashed lines indicate b...
Scheme 2: Oxidation and reduction reactions of tetrahydroquinazolines. Dashed lines indicate both cyclized or...
Figure 2: Hydrolysis of the aminal core of tetrahydroquinazolines 1 into the corresponding diamines 2 and ald...
Scheme 3: Reagents and conditions: (i) MeI, DIPEA, DMAc, 40 °C, 24 h; (ii) R1-NH2 or MeNH3Cl and Et3N, DMF, 4...
Scheme 4: Reagents and conditions: (a) (i) MeNH3Cl, Et3N, DMF, 70 °C, 3 h; (ii) AcOH, 70 °C, 4 h; (iii) n-PrB...
Figure 3: pH-Stability test of the aminal core toward hydrolysis in dependency of different substitution patt...
Figure 4: Kinetic analysis of hydrolysis of reference compound 8a in dependency of different pH values and ca...
Figure 5: Differences in energy along the reaction coordinate using the functional B3LYP-D3 for the hydrolysi...
Figure 6: Reaction equilibrium between tetrahydroquinazoline 1, the corresponding diamine 2 and aldehyde 3 in...
Figure 7: Minimum energy conformers in their neutral form with (a) an axial orientation of the phenyl system ...
Rearrangements of organic peroxides and related processes
- Ivan A. Yaremenko,
- Vera A. Vil’,
- Dmitry V. Demchuk and
- Alexander O. Terent’ev
Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162
- to alkyl-containing ketones to give the target products in yields of 30–91% and good regioselectivity 7:1 to 20:1 (Scheme 28) [261]. Asymmetric oxidation: Asymmetric Baeyer–Villiger oxidation reactions can be performed using chiral acetals, organic hydroperoxides, chiral metal complexes and
- observed with the peptide catalyst (Scheme 33) [285]. Versatility of the Baeyer–Villiger reaction with respect to starting reactants: The Baeyer–Villiger reaction cannot only be performed with ketones but also with acetals and aldimines as the starting substrates. The oxidation of cycloalkanone acetals
- involves the formation of solvolytically generated cyclobutyl hydroperoxides 177 followed by the rearrangement of the latter into oxa-bridged, hydroperoxyhemiketals 176 (Scheme 53). The fragmentation of hydroperoxy acetals 178a–e in the presence of Ca(OCl)2 or t-BuOCl as the catalysts in CH3CN generating
Graphical Abstract
Figure 1: The named transformations considered in this review.
Scheme 1: The Baeyer–Villiger oxidation.
Scheme 2: The general mechanism of the peracid-promoted Baeyer–Villiger oxidation.
Scheme 3: General mechanism of the Lewis acid-catalyzed Baeyer–Villiger rearrangement.
Scheme 4: The theoretically studied mechanism of the BV oxidation reaction promoted by H2O2 and the Lewis aci...
Scheme 5: Proton movements in the transition states of the Baeyer–Villiger oxidation.
Scheme 6: The dependence of the course of the Baeyer–Villiger oxidation on the type of O–O-bond cleavage in t...
Scheme 7: The acid-catalyzed Baeyer–Villiger oxidation of cyclic epoxy ketones 22.
Scheme 8: Oxidation of isophorone oxide 29.
Scheme 9: Synthesis of acyl phosphate 32 from acyl phosphonate 31.
Scheme 10: Synthesis of aflatoxin B2 (36).
Scheme 11: The Baeyer–Villiger rearrangement of ketones 37 to lactones 38.
Scheme 12: Synthesis of 3,4-dimethoxybenzoic acid (40) via Baeyer–Villiger oxidation.
Scheme 13: Oxone transforms α,β-unsaturated ketones 43 into vinyl acetates 44.
Scheme 14: The Baeyer–Villiger oxidation of ketones 45 using diaryl diselenide and hydrogen peroxide.
Scheme 15: Baeyer–Villiger oxidation of (E)-2-methylenecyclobutanones.
Scheme 16: Oxidation of β-ionone (56) by H2O2/(BnSe)2 with formation of (E)-2-(2,6,6-trimethylcyclohex-1-en-1-...
Scheme 17: The mechanism of oxidation of ketones 58a–f by hydrogen peroxide in the presence of arsonated polys...
Scheme 18: Oxidation of ketone (58b) by H2O2 to 6-methylcaprolactone (59b) catalyzed by Pt complex 66·BF4.
Scheme 19: Oxidation of ketones 67 with H2O2 in the presence of [(dppb}Pt(µ-OH)]22+.
Scheme 20: The mechanism of oxidation of ketones 67 in the presence of [(dppb}Pt(µ-OH)]22+ and H2O2.
Scheme 21: Oxidation of benzaldehydes 69 in the presence of the H2O2/MeReO3 system.
Scheme 22: Oxidation of acetophenones 72 in the presence of the H2O2/MeReO3 system.
Scheme 23: Baeyer–Villiger oxidation of 2-adamantanone (45c) in the presence of Sn-containing mesoporous silic...
Scheme 24: Aerobic Baeyer–Villiger oxidation of ketones 76 using metal-free carbon.
Scheme 25: A regioselective Baeyer-Villiger oxidation of functionalized cyclohexenones 78 into a dihydrooxepin...
Scheme 26: The oxidation of aldehydes and ketones 80 by H2O2 catalyzed by Co4HP2Mo15V3O62.
Scheme 27: The cleavage of ketones 82 with hydrogen peroxide in alkaline solution.
Scheme 28: Oxidation of ketones 85 to esters 86 with H2O2–urea in the presence of KHCO3.
Scheme 29: Mechanism of the asymmetric oxidation of cyclopentane-1,2-dione 87a with the Ti(OiPr)4/(+)DET/t-BuO...
Scheme 30: The oxidation of cis-4-tert-butyl-2-fluorocyclohexanone (93) with m-chloroperbenzoic acid.
Scheme 31: The mechanism of the asymmetric oxidation of 3-substituted cyclobutanone 96a in the presence of chi...
Scheme 32: Enantioselective Baeyer–Villiger oxidation of cyclic ketones 98.
Scheme 33: Regio- and enantioselective Baeyer–Villiger oxidation of cyclic ketones 101.
Scheme 34: The proposed mechanism of the Baeyer–Villiger oxidation of acetal 105f.
Scheme 35: Synthesis of hydroxy-10H-acridin-9-one 117 from tetramethoxyanthracene 114.
Scheme 36: The Baeyer–Villiger oxidation of the fully substituted pyrrole 120.
Scheme 37: The Criegee rearrangement.
Scheme 38: The mechanism of the Criegee reaction of a peracid with a tertiary alcohol 122.
Scheme 39: Criegee rearrangement of decaline ethylperoxoate 127 into ketal 128.
Scheme 40: The ionic cleavage of 2-methoxy-2-propyl perester 129.
Scheme 41: The Criegee rearrangement of α-methoxy hydroperoxide 136.
Scheme 42: Synthesis of enol esters and acetals via the Criegee rearrangement.
Scheme 43: Proposed mechanism of the transformation of 1-hydroperoxy-2-oxabicycloalkanones 147a–d.
Scheme 44: Transformation of 3-hydroxy-1,2-dioxolanes 151 into diketone derivatives 152.
Scheme 45: Criegee rearrangement of peroxide 153 with the mono-, di-, and tri-O-insertion.
Scheme 46: The sequential Criegee rearrangements of adamantanes 157a,b.
Scheme 47: Synthesis of diaryl carbonates 160a–d from triarylmethanols 159a–d through successive oxygen insert...
Scheme 48: The synthesis of sesquiterpenes 162 from ketone 161 with a Criegee rearrangement as one key step.
Scheme 49: Synthesis of trans-hydrindan derivatives 164, 165.
Scheme 50: The Hock rearrangement.
Scheme 51: The general scheme of the cumene process.
Scheme 52: The Hock rearrangement of aliphatic hydroperoxides.
Scheme 53: The mechanism of solvolysis of brosylates 174a–c and spiro cyclopropyl carbinols 175a–c in THF/H2O2....
Scheme 54: The fragmentation mechanism of hydroperoxy acetals 178 to esters 179.
Scheme 55: The acid-catalyzed rearrangement of phenylcyclopentyl hydroperoxide 181.
Scheme 56: The peroxidation of tertiary alcohols in the presence of a catalytic amount of acid.
Scheme 57: The acid-catalyzed reaction of bicyclic secondary alcohols 192 with hydrogen peroxide.
Scheme 58: The photooxidation of 5,6-disubstituted 3,4-dihydro-2H-pyrans 196.
Scheme 59: The oxidation of tertiary alcohols 200a–g, 203a,b, and 206.
Scheme 60: Transformation of functional peroxide 209 leading to 2,3-disubstitued furans 210 in one step.
Scheme 61: The synthesis of carbazoles 213 via peroxide rearrangement.
Scheme 62: The construction of C–N bonds using the Hock rearrangement.
Scheme 63: The synthesis of moiety 218 from 217 which is a structural motif in the antitumor–antibiotic of CC-...
Scheme 64: The in vivo oxidation steps of cholesterol (219) by singlet oxygen.
Scheme 65: The proposed mechanism of the rearrangement of cholesterol-5α-OOH 220.
Scheme 66: Photochemical route to artemisinin via Hock rearrangement of 223.
Scheme 67: The Kornblum–DeLaMare rearrangement.
Scheme 68: Kornblum–DeLaMare transformation of 1-phenylethyl tert-butyl peroxide (225).
Scheme 69: The synthesis 4-hydroxyenones 230 from peroxide 229.
Scheme 70: The Kornblum–DeLaMare rearrangement of peroxide 232.
Scheme 71: The reduction of peroxide 234.
Scheme 72: The Kornblum–DeLaMare rearrangement of endoperoxide 236.
Scheme 73: The rearrangement of peroxide 238 under Kornblum–DeLaMare conditions.
Scheme 74: The proposed mechanism of rearrangement of peroxide 238.
Scheme 75: The Kornblum–DeLaMare rearrangement of peroxides 242a,b.
Scheme 76: The base-catalyzed rearrangements of bicyclic endoperoxides having electron-withdrawing substituent...
Scheme 77: The base-catalyzed rearrangements of bicyclic endoperoxides 249a,b having electron-donating substit...
Scheme 78: The base-catalyzed rearrangements of bridge-head substituted bicyclic endoperoxides 251a,b.
Scheme 79: The Kornblum–DeLaMare rearrangement of hydroperoxide 253.
Scheme 80: Synthesis of β-hydroxy hydroperoxide 254 from endoperoxide 253.
Scheme 81: The amine-catalyzed rearrangement of bicyclic endoperoxide 263.
Scheme 82: The base-catalyzed rearrangement of meso-endoperoxide 268 into 269.
Scheme 83: The photooxidation of 271 and subsequent Kornblum–DeLaMare reaction.
Scheme 84: The Kornblum–DeLaMare rearrangement as one step in the oxidation reaction of enamines.
Scheme 85: The Kornblum–DeLaMare rearrangement of 3,5-dihydro-1,2-dioxenes 284, 1,2-dioxanes 286, and tert-but...
Scheme 86: The Kornblum–DeLaMare rearrangement of epoxy dioxanes 290a–d.
Scheme 87: Rearrangement of prostaglandin H2 292.
Scheme 88: The synthesis of epicoccin G (297).
Scheme 89: The Kornblum–DeLaMare rearrangement used in the synthesis of phomactin A.
Scheme 90: The Kornblum–DeLaMare rearrangement in the synthesis of 3H-quinazolin-4-one 303.
Scheme 91: The Kornblum–DeLaMare rearrangement in the synthesis of dolabriferol (308).
Scheme 92: Sequential transformation of 3-substituted 2-pyridones 309 into 3-hydroxypyridine-2,6-diones 311 in...
Scheme 93: The Kornblum–DeLaMare rearrangement of peroxide 312 into hydroxy enone 313.
Scheme 94: The Kornblum–DeLaMare rearrangement in the synthesis of polyfunctionalized carbonyl compounds 317.
Scheme 95: The Kornblum–DeLaMare rearrangement in the synthesis of (Z)-β-perfluoroalkylenaminones 320.
Scheme 96: The Kornblum–DeLaMare rearrangement in the synthesis of γ-ketoester 322.
Scheme 97: The Kornblum–DeLaMare rearrangement in the synthesis of diterpenoids 326 and 328.
Scheme 98: The synthesis of natural products hainanolidol (331) and harringtonolide (332) from peroxide 329.
Scheme 99: The synthesis of trans-fused butyrolactones 339 and 340.
Scheme 100: The synthesis of leucosceptroid C (343) and leucosceptroid P (344) via the Kornblum–DeLaMare rearra...
Scheme 101: The Dakin oxidation of arylaldehydes or acetophenones.
Scheme 102: The mechanism of the Dakin oxidation.
Scheme 103: A solvent-free Dakin reaction of aromatic aldehydes 356.
Scheme 104: The organocatalytic Dakin oxidation of electron-rich arylaldehydes 358.
Scheme 105: The Dakin oxidation of electron-rich arylaldehydes 361.
Scheme 106: The Dakin oxidation of arylaldehydes 358 in water extract of banana (WEB).
Scheme 107: A one-pot approach towards indolo[2,1-b]quinazolines 364 from indole-3-carbaldehydes 363 through th...
Scheme 108: The synthesis of phenols 367a–c from benzaldehydes 366a-c via acid-catalyzed Dakin oxidation.
Scheme 109: Possible transformation paths of the highly polarized boric acid coordinated H2O2–aldehyde adduct 3...
Scheme 110: The Elbs oxidation of phenols 375 to hydroquinones.
Scheme 111: The mechanism of the Elbs persulfate oxidation of phenols 375 affording p-hydroquinones 376.
Scheme 112: Oxidation of 2-pyridones 380 under Elbs persulfate oxidation conditions.
Scheme 113: Synthesis of 3-hydroxy-4-pyridone (384) via an Elbs oxidation of 4-pyridone (382).
Scheme 114: The Schenck rearrangement.
Scheme 115: The Smith rearrangement.
Scheme 116: Three main pathways of the Schenck rearrangement.
Scheme 117: The isomerization of hydroperoxides 388 and 389.
Scheme 118: Trapping of dioxacyclopentyl radical 392 by oxygen.
Scheme 119: The hypothetical mechanism of the Schenck rearrangement of peroxide 394.
Scheme 120: The autoxidation of oleic acid (397) with the use of labeled isotope 18O2.
Scheme 121: The rearrangement of 18O-labeled hydroperoxide 400 under an atmosphere of 16O2.
Scheme 122: The rearrangement of the oleate-derived allylic hydroperoxides (S)-421 and (R)-425.
Scheme 123: Mechanisms of Schenck and Smith rearrangements.
Scheme 124: The rearrangement and cyclization of 433.
Scheme 125: The Wieland rearrangement.
Scheme 126: The rearrangement of bis(triphenylsilyl) 439 or bis(triphenylgermyl) 441 peroxides.
Scheme 127: The oxidative transformation of cyclic ketones.
Scheme 128: The hydroxylation of cyclohexene (447) in the presence of tungstic acid.
Scheme 129: The oxidation of cyclohexene (447) under the action of hydrogen peroxide.
Scheme 130: The reaction of butenylacetylacetone 455 with hydrogen peroxide.
Scheme 131: The oxidation of bridged 1,2,4,5-tetraoxanes.
Scheme 132: The proposed mechanism for the oxidation of bridged 1,2,4,5-tetraoxanes.
Scheme 133: The rearrangement of ozonides.
Scheme 134: The acid-catalyzed oxidative rearrangement of malondialdehydes 462 under the action of H2O2.
Scheme 135: Pathways of the Lewis acid-catalyzed cleavage of dialkyl peroxides 465 and ozonides 466.
Scheme 136: The mechanism of the transformation of (tert-butyldioxy)cyclohexanedienones 472.
Scheme 137: The synthesis of Vitamin K3 from 472a.
Scheme 138: Proposed mechanism for the transformation of 478d into silylated endoperoxide 479d.
Scheme 139: The rearrangement of hydroperoxide 485 to form diketone 486.
Scheme 140: The base-catalyzed rearrangement of cyclic peroxides 488a–g.
Scheme 141: Synthesis of chiral epoxides and aldols from peroxy hemiketals 491.
Scheme 142: The multistep transformation of (R)-carvone (494) to endoperoxides 496a–e.
Scheme 143: The decomposition of anthracene endoperoxide 499.
Scheme 144: Synthesis of esters 503 from aldehydes 501 via rearrangement of peroxides 502.
Scheme 145: Two possible paths for the base-promoted decomposition of α-azidoperoxides 502.
Scheme 146: The Story decomposition of cyclic diperoxide 506a.
Scheme 147: The Story decomposition of cyclic triperoxide 506b.
Scheme 148: The thermal rearrangement of endoperoxides A into diepoxides B.
Scheme 149: The transformation of peroxide 510 in the synthesis of stemolide (511).
Scheme 150: The possible mechanism of the rearrangement of endoperoxide 261g.
Scheme 151: The photooxidation of indene 517.
Scheme 152: The isomerization of ascaridole (523).
Scheme 153: The isomerization of peroxide 525.
Scheme 154: The thermal transformation of endoperoxide 355.
Scheme 155: The photooxidation of cyclopentadiene (529) at a temperature higher than 0 °C.
Scheme 156: The thermal rearrangement of endoperoxides 538a,b.
Scheme 157: The transformation of peroxides 541.
Scheme 158: The thermal rearrangements of strained cyclic peroxides.
Scheme 159: The thermal rearrangement of diacyl peroxide 551 in the synthesis of C4-epi-lomaiviticin B core 553....
Scheme 160: The 1O2 oxidation of tryptophan (554) and rearrangement of dioxetane intermediate 555.
Scheme 161: The Fe(II)-promoted cleavage of aryl-substituted bicyclic peroxides.
Scheme 162: The proposed mechanism of the Fe(II)-promoted rearrangement of 557a–c.
Scheme 163: The reaction of dioxolane 563 with Fe(II) sulfate.
Scheme 164: Fe(II)-promoted rearrangement of 1,2-dioxane 565.
Scheme 165: Fe(II) cysteinate-promoted rearrangement of 1,2-dioxolane 568.
Scheme 166: The transformation of 1,2-dioxanes 572a–c under the action of FeCl2.
Scheme 167: Fe(II) cysteinate-promoted transformation of tetraoxane 574.
Scheme 168: The CoTPP-catalyzed transformation of bicyclic endoperoxides 600a–d.
Scheme 169: The CoTPP-catalyzed transformation of epoxy-1,2-dioxanes.
Scheme 170: The Ru(II)-catalyzed reactions of 1,4-endoperoxide 261g.
Scheme 171: The Ru(II)-catalyzed transformation as a key step in the synthesis of elyiapyrone A (610) from 1,4-...
Scheme 172: Peroxides with antimalarial activity.
Scheme 173: The interaction of iron ions with artemisinin (616).
Scheme 174: The interaction of FeCl2 with 1,2-dioxanes 623, 624.
Scheme 175: The mechanism of reaction 623 and 624 with Fe(II)Cl2.
Scheme 176: The reaction of bicyclic natural endoperoxides G3-factors 631–633 with FeSO4.
Scheme 177: The transformation of terpene cardamom peroxide 639.
Scheme 178: The different ways of the cleavage of tetraoxane 643.
Scheme 179: The LC–MS analysis of interaction of tetraoxane 646 with iron(II)heme 647.
Scheme 180: The rearrangement of 3,6-epidioxy-1,10-bisaboladiene (EDBD, 649).
Scheme 181: Easily oxidized substrates.
Scheme 182: Biopathway of synthesis of prostaglandins.
Scheme 183: The reduction and rearrangements of isoprostanes.
Scheme 184: The partial mechanism for linoleate 658 oxidation.
Scheme 185: The transformation of lipid hydroperoxide.
Scheme 186: The acid-catalyzed cleavage of the product from free-radical oxidation of cholesterol (667).
Scheme 187: Two pathways of catechols oxidation.
Scheme 188: Criegee-like or Hock-like rearrangement of the intermediate hydroperoxide 675 in dioxygenase enzyme...
Scheme 189: Carotinoides 679 cleavage by carotenoid cleavage dioxygenases.
Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides
- Franziska Hemmerling and
- Frank Hahn
Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148
- presence of Lewis acids is a common synthetic strategy for making pyrans and furans. Hemiacetals are also biosynthesis intermediates where they are transformed into individually functionalised heterocycles or acetals. In many cases, these hemiacetals are also appropriately activated to react further
- 1.1.3. 1.3 Polycyclic systems During the biosynthesis of ionophoric terrestrial and marine polyethers, polyolefinic PKS products are first polyepoxidised and these epoxides are then opened in a so-called zipper mechanism that installs furan and/or pyran rings as well as cyclic acetals, if carbonyl
Graphical Abstract
Scheme 1: Schematic description of the cyclisation reaction catalysed by TE domains. In most cases, the nucle...
Scheme 2: Mechanisms for the formation of oxygen heterocycles. The degree of substitution can differ from tha...
Scheme 3: Pyran-ring formation in pederin (24) biosynthesis. Incubation of recombinant PedPS7 with substrate ...
Scheme 4: The domain AmbDH3 from ambruticin biosynthesis catalyses the dehydration of 25 and subsequent cycli...
Scheme 5: SalBIII catalyses dehydration of 29 and subsequent cyclisation to tetrahydropyran 30 [18].
Figure 1: All pyranonaphtoquinones contain either the naphtha[2,3-c]pyran-5,10-dione (32) or the regioisomeri...
Scheme 6: Pyran-ring formation in actinorhodin (34) biosynthesis. DNPA: 4-dihydro-9-hydroxy-1-methyl-10-oxo-3H...
Scheme 7: Pyran formation in granaticin (36) biosynthesis. DNPA: 4-dihydro-9-hydroxy-1-methyl-10-oxo-3H-napht...
Scheme 8: Pyran formation in alnumycin (37) biosynthesis. Adapted from [21].
Scheme 9: Biosynthesis of pseudomonic acid A (61). The pyran ring is initially formed in 57 after dehydrogena...
Scheme 10: Epoxidation–cyclisation leads to the formation of the tetrahydropyran ring in the western part of t...
Scheme 11: a) Nonactin (70) is formed from heterodimers of (−)(+)-dimeric nonactic acid and (+)(−)-dimeric non...
Figure 2: Pamamycins (73) are macrodiolide antibiotics containing three tetrahydrofuran moieties, which are a...
Scheme 12: A PS domain homolog in oocydin A (76) biosynthesis is proposed to catalyse furan formation via an o...
Scheme 13: Mechanism of oxidation–furan cyclisation by AurH, which converts (+)-deoxyaureothin (77) into (+)-a...
Scheme 14: Leupyrrin A2 (80) and the proposed biosynthesis of its furylidene moiety [69,70].
Scheme 15: Asperfuranone (93) biosynthesis, adapted from [75].
Figure 3: The four major aflatoxins produced by Aspergilli are the types B1, B2, G1 and G2 (94–97). In the di...
Scheme 16: Overview on aflatoxin B1 (94) biosynthesis. HOMST = 11-hydroxy-O-methylsterigmatocystin [78,79,82-106].
Scheme 17: A zipper mechanism leads to the formation of oxygen heterocycles in monensin biosynthesis [109-111].
Scheme 18: Formation of the 2,6-dioxabicyclo[3.2.1]octane (DBO) ring system in aurovertin B (118) biosynthesis ...
Figure 4: Structures of the epoxide-containing polyketides epothilone A (119) and oleandomycin (120) [123-125].
Scheme 19: Structures of phoslactomycin B (121) (a) and jerangolid A (122) (b). The heterocycle-forming steps ...
Scheme 20: a) Structures of rhizoxin (130) and cycloheximide (131). Model for the formation of δ-lactones (b) ...
Scheme 21: EncM catalyses a dual oxidation sequence and following processing of the highly reactive intermedia...
Figure 5: Mesomeric structures of tetronates [138,139].
Figure 6: Structures of tetronates for which gene clusters have been sequenced. The tetronate moiety is shown...
Scheme 22: Conserved steps for formation and processing in several 3-acyl-tetronate biosynthetic pathways were...
Scheme 23: In versipelostatin A (153) biosynthesis, VstJ is a candidate enzyme for catalysing the [4 + 2] cycl...
Scheme 24: a) Structures of some thiotetronate antibiotics. b) Biosynthesis of thiolactomycin (165) as propose...
Scheme 25: Aureusidine synthase (AS) catalyses phenolic oxidation and conjugate addition of chalcones leading ...
Scheme 26: a) Oxidative cyclisation is a key step in the biosynthesis of spirobenzofuranes 189, 192 and 193. b...
Scheme 27: A bicyclisation mechanism forms a β-lactone and a pyrrolidinone and removes the precursor from the ...
Scheme 28: Spontaneous cyclisation leads to off-loading of ebelactone A (201) from the PKS machinery [163].
Scheme 29: Mechanisms for the formation of nitrogen heterocycles.
Scheme 30: Biosynthesis of highly substituted α-pyridinones. a) Feeding experiments confirmed the polyketide o...
Scheme 31: Acridone synthase (ACS) catalyses the formation of 1,3-dihydroxy-N-methylacridone (224) by condensa...
Scheme 32: A Dieckmann condensation leads to the formation of a 3-acyl-4-hydroxypyridin-2-one 227 and removes ...
Scheme 33: a) Biosynthesis of the pyridinone tenellin (234). b) A radical mechanism was proposed for the ring-...
Scheme 34: a) Oxazole-containing PKS–NRPS-derived natural products oxazolomycin (244) and conglobatin (245). b...
Scheme 35: Structure of tetramic acids 251 (a) and major tautomers of 3-acyltetramic acids 252a–d (b). Adapted...
Scheme 36: Equisetin biosynthesis. R*: terminal reductive domain. Adapted from [202].
Scheme 37: a) Polyketides for which a similar biosynthetic logic was suggested. b) Pseurotin A (256) biosynthe...
Figure 7: Representative examples of PTMs with varying ring sizes and oxidation patterns [205,206].
Scheme 38: Ikarugamycin biosynthesis. Adapted from [209-211].
Scheme 39: Tetramate formation in pyrroindomycin aglycone (279) biosynthesis [213-215].
Scheme 40: Dieckmann cyclases catalyse tetramate or 2-pyridone formation in the biosynthesis of, for example, ...
From steroids to aqueous supramolecular chemistry: an autobiographical career review
- Bruce C. Gibb
Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69
- aromatic macrocycle [25]. Interestingly, as these hosts are tetra-acetals we initially tried removing the template under acidic conditions. However, even reflux in 1:1 EtOH/H2SO4 for a week failed to affect the starting material. Evidently, under reversible conditions, a broken acetal can easily reform
Graphical Abstract
Scheme 1: The formation of a 1:1 complex and a 2:1 supramolecular nano-capsule complex from bowl-shaped “cavi...
Scheme 2: Abbreviated synthesis of 7-amino-2-phenyl-6-azaindolizine.
Figure 1: My two favorite compounds for my Ph.D. dissertation, “The Synthesis and Structural Examination of 3...
Scheme 3: An inspiring chlorination from the group of Ronald Breslow.
Scheme 4: The carceplex reaction.
Figure 2: Schematic of a cavitein.
Figure 3: General structure of zinc-TPA complexes.
Scheme 5: Stereoselective bridging of a resorcinarene with benzal halides.
Scheme 6: An eight-fold Ullman ether “weaving” reaction.
Scheme 7: Directed ortho-metallation of the deep-cavity cavitands, showing the mono-endo substituted to tetra-...
Scheme 8: Macrocycle synthesis via resorcinarene covalent templates.
Figure 4: Tris-pyridyl hosts.
Figure 5: (Center) Chemical structure of the octa-acid host. (Left and right) Respective space-filling repres...
Figure 6: Cartoons of the 2:1 host–guest complexes of estradiol (left) and cholesterol (right).
Figure 7: Representative guests for the capsular complexes formed by octa-acid (stoichiometry shown in parent...
Figure 8: A dendrimer-coated cavitand.
Figure 9: Selective oxidation of olefins by singlet oxygen.
Figure 10: a) Preferred packing motifs of methyl, pentyl and octyl guests. b) Product distribution observed fo...
Figure 11: Schematic of the competition of two esters for the capsule formed by octa-acid. The ester that bind...
Figure 12: Schematic of the inter-phase separation of propane and butane; the latter binds more strongly to th...
Figure 13: Structure of tetra-endo-methyl octa-acid (TEMOA).
Figure 14: Assembly properties of TEMOA.
Figure 15: How salts influence the association constant (Ka) for the binding of ClO4– to octa-acid (Figure 4). The ind...
(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers
- Giorgos Koutoulogenis,
- Nikolaos Kaplaneris and
- Christoforos G. Kokotos
Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48
Graphical Abstract
Scheme 1: Activation of carbonyl compounds via enamine and iminium intermediates [2].
Scheme 2: Electronic and steric interactions present in enamine activation mode [2].
Scheme 3: Electrophilic activation of carbonyl compounds by a thiourea moiety.
Scheme 4: Asymmetric synthesis of dihydro-2H-pyran-6-carboxylate 3 using organocatalyst 4 [16].
Scheme 5: Possible hydrogen-bonding for the reaction of (E)-methyl 2-oxo-4-phenylbut-3-enoate [16].
Scheme 6: Asymmetric desymmetrization of 4,4-cyclohexadienones using the Michael addition reaction with malon...
Scheme 7: The enantioselective synthesis of α,α-disubstituted cycloalkanones using catalyst 11 [18].
Scheme 8: The enantioselective synthesis of indolo- and benzoquinolidine compounds through aza-Diels–Alder re...
Scheme 9: Enantioselective [5 + 2] cycloaddition [20].
Scheme 10: Asymmetric synthesis of oxazine derivatives 26 [21].
Scheme 11: Asymmetric synthesis of bicyclo[3.3.1]nonadienone, core 30 present in (−)-huperzine [22].
Scheme 12: Asymmetric inverse electron-demand Diels-Alder reaction catalyzed by amine-thiourea 34 [23].
Scheme 13: Asymmetric entry to morphan skeletons, catalyzed by amine-thiourea 37 [24].
Scheme 14: Asymmetric transformation of (E)-2-nitroallyl acetate [25].
Scheme 15: Proposed way of activation.
Scheme 16: Asymmetric synthesis of nitrobicyclo[3.2.1]octan-2-one derivatives [26].
Scheme 17: Asymmetric tandem Michael–Henry reaction catalyzed by 50 [27].
Scheme 18: Asymmetric Diels–Alder reactions of 3-vinylindoles 51 [29].
Scheme 19: Proposed transition state and activation mode of the asymmetric Diels–Alder reactions of 3-vinylind...
Scheme 20: Desymmetrization of meso-anhydrides by Chin, Song and co-workers [30].
Scheme 21: Desymmetrization of meso-anhydrides by Connon and co-workers [31].
Scheme 22: Asymmetric intramolecular Michael reaction [32].
Scheme 23: Asymmetric addition of malonate to 3-nitro-2H-chromenes 67 [33].
Scheme 24: Intramolecular desymmetrization through an intramolecular aza-Michael reaction [34].
Scheme 25: Enantioselective synthesis of (−)-mesembrine [34].
Scheme 26: A novel asymmetric Michael–Michael reaction [35].
Scheme 27: Asymmetric three-component reaction catalyzed by Takemoto’s catalyst 77 [46].
Scheme 28: Asymmetric domino Michael–Henry reaction [47].
Scheme 29: Asymmetric domino Michael–Henry reaction [48].
Scheme 30: Enantioselective synthesis of derivatives of 3,4-dihydro-2H-pyran 89 [49].
Scheme 31: Asymmetric addition of α,α-dicyano olefins 90 to 3-nitro-2H-chromenes 91 [50].
Scheme 32: Asymmetric three-component reaction producing 2,6-diazabicyclo[2.2.2]octanones 95 [51].
Scheme 33: Asymmetric double Michael reaction producing substituted chromans 99 [52].
Scheme 34: Enantioselective synthesis of multi-functionalized spiro oxindole dienes 106 [53].
Scheme 35: Organocatalyzed Michael aldol cyclization [54].
Scheme 36: Asymmetric synthesis of dihydrocoumarins [55].
Scheme 37: Asymmetric double Michael reaction en route to tetrasubstituted cyclohexenols [56].
Scheme 38: Asymmetric synthesis of α-trifluoromethyl-dihydropyrans 121 [58].
Scheme 39: Tyrosine-derived tertiary amino-thiourea 123 catalyzed Michael hemiaketalization reaction [59].
Scheme 40: Enantioselective entry to bicyclo[3.2.1]octane unit [60].
Scheme 41: Asymmetric synthesis of spiro[4-cyclohexanone-1,3’-oxindoline] 126 [61].
Scheme 42: Kinetic resolution of 3-nitro-2H-chromene 130 [62].
Scheme 43: Asymmetric synthesis of chromanes 136 [63].
Scheme 44: Wang’s utilization of β-unsaturated α-ketoesters 87 [64,65].
Scheme 45: Asymmetric entry to trifluoromethyl-substituted dihydropyrans 144 [66].
Scheme 46: Phenylalanine-derived thiourea-catalyzed domino Michael hemiaketalization reaction [67].
Scheme 47: Asymmetric synthesis of α-trichloromethyldihydropyrans 149 [68].
Scheme 48: Takemoto’s thiourea-catalyzed domino Michael hemiaketalization reaction [69].
Scheme 49: Asymmetric synthesis of densely substituted cyclohexanes [70].
Scheme 50: Enantioselective synthesis of polysubstituted chromeno [4,3-b]pyrrolidine derivatines 157 [71].
Scheme 51: Enantioselective synthesis of spiro-fused cyclohexanone/5-oxazolone scaffolds 162 [72].
Scheme 52: Utilizing 2-mercaptobenzaldehydes 163 in cascade processes [73,74].
Scheme 53: Proposed transition state of the initial sulfa-Michael step [74].
Scheme 54: Asymmetric thiochroman synthesis via dynamic kinetic resolution [75].
Scheme 55: Enantioselective synthesis of thiochromans [76].
Scheme 56: Enantioselective synthesis of chromans and thiochromans synthesis [77].
Scheme 57: Enantioselective sulfa-Michael aldol reaction en route to spiro compounds [78].
Scheme 58: Enantioselective synthesis of 4-aminobenzo(thio)pyrans 179 [79].
Scheme 59: Asymmetric synthesis of tetrahydroquinolines [80].
Scheme 60: Novel asymmetric Mannich–Michael sequence producing tetrahydroquinolines 186 [81].
Scheme 61: Enantioselective synthesis of biologically interesting chromanes 190 and 191 [82].
Scheme 62: Asymmetric tandem Henry–Michael reaction [83].
Scheme 63: An asymmetric synthesis of substituted cyclohexanes via a dynamic kinetic resolution [84].
Scheme 64: Three component-organocascade initiated by Knoevenagel reaction [85].
Scheme 65: Asymmetric Michael reaction catalyzed by catalysts 57 and 211 [86].
Scheme 66: Proposed mechanism for the asymmetric Michael reaction catalyzed by catalysts 57 and 211 [86].
Scheme 67: Asymmetric facile synthesis of hexasubstituted cyclohexanes [87].
Scheme 68: Dual activation catalytic mechanism [87].
Scheme 69: Asymmetric Michael–Michael/aldol reaction catalyzed by catalysts 57, 219 and 214 [88].
Scheme 70: Asymmetric synthesis of substituted cyclohexane derivatives, using catalysts 57 and 223 [89].
Scheme 71: Asymmetric synthesis of substituted piperidine derivatives, using catalysts 223 and 228 [90].
Scheme 72: Asymmetric synthesis of endo-exo spiro-dihydropyran-oxindole derivatives catalyzed by catalyst 232 [91]....
Scheme 73: Asymmetric synthesis of carbazole spiroxindole derivatives, using catalyst 236 [92].
Scheme 74: Enantioselective formal [2 + 2] cycloaddition of enal 209 with nitroalkene 210, using catalysts 23 ...
Scheme 75: Asymmetric synthesis of polycyclized hydroxylactams derivatives, using catalyst 242 [94].
Scheme 76: Asymmetric synthesis of product 243, using catalyst 246 [95].
Scheme 77: Formation of the α-stereoselective acetals 248 from the corresponding enol ether 247, using catalys...
Scheme 78: Selective glycosidation, catalyzed by Shreiner’s catalyst 23 [97].
Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin
- Daniel I. Hădărugă,
- Mustafa Ünlüsayin,
- Alexandra T. Gruia,
- Cristina Birău (Mitroi),
- Gerlinde Rusu and
- Nicoleta G. Hădărugă
Beilstein J. Org. Chem. 2016, 12, 179–191, doi:10.3762/bjoc.12.20
- profile of nondegraded and degraded ASO was obtained by GC–MS analysis of the corresponding methyl esters (as well as acetals and ketals of FA degradation compounds). For derivatization, approximately 20 mg of ASO or the corresponding sample was dissolved in 3 mL of boron trifluoride–methanol solution in
Graphical Abstract
Figure 1: Superimposed thermograms for β-CD (solid line) and (a) β-CD/ASO_1:1_a&b (duplicate) or (b) β-CD/ASO...
Figure 2: Superimposed DSC data for β-CD (solid line) and (a) β-CD/ASO_3:1_a&b (duplicate) or (b) β-CD/ASO_3:...
Figure 3: The equation of the KF chemical reaction.
Figure 4: Superimposed volume versus time linear correlations (all three specific intervals) from the KFT ana...
Figure 5: Superimposed volume versus time linear correlations (all three specific intervals) from the KFT ana...
Scope and limitations of the dual-gold-catalysed hydrophenoxylation of alkynes
- Adrián Gómez-Suárez,
- Yoshihiro Oonishi,
- Anthony R. Martin and
- Steven P. Nolan
Beilstein J. Org. Chem. 2016, 12, 172–178, doi:10.3762/bjoc.12.19
- (3ad), acetals (3ae) and naphthyls (3af) were well tolerated and the corresponding vinyl ethers were obtained in moderate to high yields (50–98%). On the contrary, the use of azide (3ag) or boronic ester (3ah) functionalities did not afford the desired products [29]. The latter case can be explained
- . 50 substrates, thus demonstrating the robustness and synthetic versatility of the methodology. The protocol tolerates a wide range of functional groups, such as nitriles, ketones, esters, aldehydes, acetals, naphthyls or allyls. Furthermore, we have successfully used polyphenols in a milder and more
Graphical Abstract
Scheme 1: Dual-gold-catalysed hydrophenoxylation of alkynes.
Scheme 2: Exploring the functional group tolerance. Reaction conditions: 1a (0.50 mmol, 1 equiv), 2a–o (0.55 ...
Scheme 3: Hydrophenoxylation using polyphenols. Reaction conditions: 1a (1 mmol, 2 equiv), 2p–s (0.50 mmol, 1...
Scheme 4: Hydrophenoxylation of (un)symmetrical alkynes. Reaction conditions: 1b–k (0.50 mmol, 1 equiv), 2t (...
Scheme 5: Regioselective hydrophenoxylation of unsymmetrical alkynes. Reaction conditions: 1l–p (1 equiv), 2a...
Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions
- Jixin Liu,
- Srimoyee Dasgupta and
- Mary P. Watson
Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290
- /BnBox catalyst, moderate to high yields and enantioselectivities were achieved in the addition of arylalkynes. Both yields and ee’s drop with vinyl- or alkylalkynes. Recently, we have demonstrated that enantioselective, copper-catalyzed alkynylations of oxocarbenium ions derived from chromene acetals 43
- can also be achieved in high yields and ee’s (Scheme 16) [56]. In this case, the reaction concentration has a significant impact on the enantioselectivity. We also observed that the alkynylation of chromene acetals with electron-donating substituents proceeds in higher ee’s than less electron-rich
Graphical Abstract
Figure 1: Chiral ligands utilized in copper-catalyzed alkynylations of cyclic iminium and oxocarbenium ions.
Scheme 1: Li’s alkynylation of acyclic N-arylimines.
Scheme 2: Knochel’s alkynylation of acyclic N-alkylenamines.
Scheme 3: Li’s CDC of tetrahydroisoquinolines and alkynes.
Scheme 4: Li’s alkynylation of N-aryldihydroisoquinolinium ions.
Scheme 5: Schreiber’s alkynylation of N-alkylisoquinolinium ions.
Scheme 6: Ma’s alkynylation of pyridium ions.
Scheme 7: Arndtsen’s alkynylation of cyclic iminium ions.
Scheme 8: Maruoka’s alkynylation of azomethine imines.
Scheme 9: Su’s CDC of tetrahydroisoquinolines and alkynes under ball milling conditions.
Scheme 10: Ma’s A3-coupling.
Scheme 11: Li’s CDC reaction using photoredox catalysis.
Scheme 12: Liu’s CDC reaction of N-carbamoyltetrahydroisoquinolines. T+BF4– = 2,2,6,6-tetramethylpiperidine N-...
Scheme 13: Aponick’s alkynylation of N-carbomoylquinolinium ions using StackPhos as ligand.
Scheme 14: Carreira’s enantioselective, catalytic alkynylation of aldehydes.
Scheme 15: Watson’s alkynylation of isochroman oxocarbenium ions.
Scheme 16: Watson’s alkynylation of chromene oxocarbenium ions.
Scheme 17: Watson’s alkynylation to set diaryl tetrasubstituted stereocenters.
C–H bond halogenation catalyzed or mediated by copper: an overview
- Wenyan Hao and
- Yunyun Liu
Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230
- alkenes via C–H cleavage is much less known in literature. In 2014, Yu and co-workers [66] reported the cascade synthesis of functionalized pyrrolones 66 via the dual C–H functionalization of α-alkenoylketene N,S-acetals 65. The construction of the products involved the oxidative alkene C–H amination and
Graphical Abstract
Scheme 1: Copper-catalyzed C–H bond halogenation of 2-arylpyridine.
Scheme 2: ortho-Chlorination of 2-arylpridines with acyl chlorides.
Scheme 3: Copper-catalyzed chlorination of 2-arylpyridines using LiCl.
Scheme 4: Copper-catalyzed C–H halogenation of 2-arylpyridines using LiX.
Scheme 5: Copper-mediated selective C–H halogenations of 2-arylpyridine.
Scheme 6: Copper-catalyzed C–H o-halogenation using removable DG.
Scheme 7: Copper-catalyzed C–H halogenations using PIP as DG.
Scheme 8: Copper-catalyzed quinoline C–H chlorination.
Scheme 9: Copper-catalyzed arene C–H fluorination of benzamides.
Scheme 10: Copper-catalyzed arene C–H iodination of 1,3-azoles.
Scheme 11: Copper-catalyzed C–H halogenations of phenols.
Scheme 12: Proposed mechanism for the C–H halogenation of phenols.
Scheme 13: Copper-catalyzed halogenation of electron enriched arenes.
Scheme 14: Copper-catalyzed C–H bromination of arenes.
Scheme 15: CuI-mediated synthesis of iododibenzo[b,d]furans via C–H functionalization.
Scheme 16: Cu-Mn spinel oxide-catalyzed phenol and heteroarene halogenation.
Scheme 17: Copper-catalyzed halogenations of 2-amino-1,3thiazoles.
Scheme 18: Copper-mediated chlorination and bromination of indolizines.
Scheme 19: Copper-catalyzed three-component synthesis of bromoindolizines.
Scheme 20: Copper-mediated C–H halogenation of azacalix[1]arene[3]pyridines.
Scheme 21: Copper-mediated cascade synthesis of halogenated pyrrolones.
Scheme 22: Copper-mediated alkene C–H chlorination in spirothienooxindole.
Scheme 23: Copper-catalyzed remote C–H chlorination of alkyl hydroperoxides.
Scheme 24: Copper-catalyzed C–H fluorination of alkanes.
Scheme 25: Copper-catalyzed or mediated C–H halogenations of active C(sp3)-bonds.
An efficient synthesis of N-substituted 3-nitrothiophen-2-amines
- Sundaravel Vivek Kumar,
- Shanmugam Muthusubramanian,
- J. Carlos Menéndez and
- Subbu Perumal
Beilstein J. Org. Chem. 2015, 11, 1707–1712, doi:10.3762/bjoc.11.185
- transformation generates two C–C bonds in a single operation and presumably proceeds through a reaction sequence comprising 2-mercaptoacetaldehyde generation, nucleophilic carbonyl addition, annelation and elimination steps. Keywords: C–C bond generation; nitroarenes; nitroketene acetals; sulfur heterocycles
Graphical Abstract
Figure 1: Selected examples of biologically active 2-aminothiophene derivatives.
Scheme 1: Some strategies for the synthesis of 2-aryl/alkylaminothiophenes and 3-nitrothiophenes.
Scheme 2: Our plan for the synthesis of N-substituted 3-nitrothiophen-2-amines.
Scheme 3: Synthesis of N-substituted 3-nitrothiophen-2-amines.
Figure 2: X-ray diffraction study of compound 3p.
Scheme 4: Proposed reaction sequence leading to the formation of 3.
A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones
- Marcelo Isidoro P. Reis,
- Vinícius R. Campos,
- Jackson A. L. C. Resende,
- Fernando C. Silva and
- Vitor F. Ferreira
Beilstein J. Org. Chem. 2015, 11, 1235–1240, doi:10.3762/bjoc.11.137
- equivalents of alkyl- or aryl-formimines in situ. The latter compounds may serve as electrophilic agents for aminoalkylation reactions. Our research group also investigated the aminoalkylation of 2-amino-1,4-naphthoquinone with formaldehyde under microwave irradiation to produce two series of N,O-acetals and
- N,S-acetals. These compounds were obtained in good yields, and several of them showed promising antibacterial activity [42]. The structures of the synthesized 1,3,5-triazinanes were confirmed by spectroscopic techniques such as NMR, 1H and 13C-APT, infrared spectroscopy (FTIR) and high resolution
Graphical Abstract
Figure 1: General template for heterocycle-fused 1,4-naphthoquinones.
Scheme 1: Methods for the preparation of hexahydropyrimidine-fused 1,4-naphthoquinones.
Scheme 2: Synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones 13 and 21–25.
Figure 2: ORTEP diagram of compound 18 depicted with ellipsoids drawn at the 50% probability level and the at...
Figure 3: ORTEP diagram of compound 23 depicted with ellipsoids drawn at the 50% probability level and the at...
Scheme 3: Proposed mechanism for the formation of 13 and 21–25.
Synthesis of a hexasaccharide partial sequence of hyaluronan for click chemistry and more
- Marina Bantzi,
- Stephan Rigol and
- Athanassios Giannis
Beilstein J. Org. Chem. 2015, 11, 604–607, doi:10.3762/bjoc.11.67
- TBS group at O-4''' in 59% yield [22]. The excess amount of pyridine is necessary in order to avoid cleavage of the benzylidene acetals. Following the same concept, fully protected hexasaccharide 7 was synthesized. Therefore, thioglycoside 4 was activated with NIS and TfOH and subsequently combined
Graphical Abstract
Scheme 1: Synthesis of hexasaccharide 10. Conditions: a) TfOH, NIS, 4 Å molecular sieves, DCM, 0 °C to rt; b)...
Cross-dehydrogenative coupling for the intermolecular C–O bond formation
- Igor B. Krylov,
- Vera A. Vil’ and
- Alexander O. Terent’ev
Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13
- -pyridylsulfoximines 88. Using the N-(quinolin-8-yl)amide directing group Pd(OAc)2 catalyzed the double sp3 C–H alkoxylation of 96 for the synthesis of symmetric acetals 97 and unsymmetric acetals [84] (Scheme 20). The method demonstrates good functional group tolerance and the applicability in the synthesis of
Graphical Abstract
Scheme 1: Cross-dehydrogenative coupling.
Scheme 2: Cross-dehydrogenative C–O coupling.
Scheme 3: Regioselective ortho-acetoxylation of meta-substituted arylpyridines and N-arylamides.
Scheme 4: ortho-Acyloxylation and alkoxylation of arenes directed by pyrimidine, benzoxazole, benzimidazole a...
Scheme 5: Cu(OAc)2/AgOTf/O2 oxidative system in the ortho-alkoxylation of arenes.
Scheme 6: Pd(OAc)2/persulfate oxidative system in the ortho-alkoxylation and acetoxylation of arenes with nit...
Scheme 7: ortho-Acetoxylation and methoxylation of O-methyl aryl oximes, N-phenylpyrrolidin-2-one, and (3-ben...
Scheme 8: Ruthenium-catalyzed ortho-acyloxylation of acetanilides.
Scheme 9: Acetoxylation and alkoxylation of arenes with amide directing group using Pd(OAc)2/PhI(OAc)2 oxidat...
Scheme 10: Alkoxylation of azoarenes, 2-aryloxypyridines, picolinamides, and N-(1-methyl-1-(pyridin-2-yl)ethyl...
Scheme 11: Acetoxylation of compounds containing picolinamide and quinoline-8-amine moieties using the Pd(OAc)2...
Scheme 12: (CuOH)2CO3 catalyzed oxidative ortho-etherification using air as oxidant.
Scheme 13: Copper-catalyzed aerobic alkoxylation and aryloxylation of arenes containing pyridine-N-oxide moiet...
Scheme 14: Cobalt-catalyzed aerobic alkoxylation of arenes and alkenes containing pyridine N-oxide moiety.
Scheme 15: Non-symmetric double-fold C–H ortho-acyloxylation.
Scheme 16: N-nitroso directed ortho-alkoxylation of arenes.
Scheme 17: Selective alkoxylation and acetoxylation of alkyl groups.
Scheme 18: Acetoxylation of 2-alkylpyridines and related compounds.
Scheme 19: Acyloxylation and alkoxylation of alkyl fragments of substrates containing amide or sulfoximine dir...
Scheme 20: Palladium-catalyzed double sp3 C–H alkoxylation of N-(quinolin-8-yl)amides for the synthesis of sym...
Scheme 21: Copper-catalyzed acyloxylation of methyl groups of N-(quinolin-8-yl)amides.
Scheme 22: One-pot acylation and sp3 C–H acetoxylation of oximes.
Scheme 23: Possible mechanism of oxidative esterification catalyzed by N-heterocyclic nucleophilic carbene.
Scheme 24: Oxidative esterification employing stoichiometric amounts of aldehydes and alcohols.
Scheme 25: Selective oxidative coupling of aldehydes with alcohols in the presence of amines.
Scheme 26: Iodine mediated oxidative esterification.
Scheme 27: Oxidative C–O coupling of benzyl alcohols with methylarenes under the action of Bu4NI/t-BuOOH syste...
Scheme 28: Oxidative coupling of methyl- and ethylarenes with aromatic aldehydes under the action of Bu4NI/t-B...
Scheme 29: Cross-dehydrogenative C–O coupling of aldehydes with t-BuOOH in the presence of Bu4NI.
Scheme 30: Bu4NI-catalyzed α-acyloxylation reaction of ethers and ketones with aldehydes and t-BuOOH.
Scheme 31: Oxidative coupling of aldehydes with N-hydroxyimides and hexafluoroisopropanol.
Scheme 32: Oxidative coupling of alcohols with N-hydroxyimides.
Scheme 33: Oxidative coupling of aldehydes and primary alcohols with N-hydroxyimides using (diacetoxyiodo)benz...
Scheme 34: Proposed mechanism of the oxidative coupling of aldehydes and N-hydroxysuccinimide under action of ...
Scheme 35: Oxidative coupling of aldehydes with pivalic acid (172).
Scheme 36: Oxidative C–O coupling of aldehydes with alkylarenes using the Cu(OAc)2/t-BuOOH system.
Scheme 37: Copper-catalyzed acyloxylation of C(sp3)-H bond adjacent to oxygen in ethers using benzyl alcohols.
Scheme 38: Oxidative C–O coupling of aromatic aldehydes with cycloalkanes.
Scheme 39: Ruthenium catalyzed cross-dehydrogenative coupling of primary and secondary alcohols.
Scheme 40: Cross-dehydrogenative C–O coupling reactions of β-dicarbonyl compounds with sulfonic acids, acetic ...
Scheme 41: Acyloxylation of ketones, aldehydes and β-dicarbonyl compounds using carboxylic acids and Bu4NI/t-B...
Scheme 42: Acyloxylation of ketones using Bu4NI/t-BuOOH system.
Scheme 43: Cross-dehydrogenative C–O coupling of β-dicarbonyl compounds and their heteroanalogues with N-hydro...
Scheme 44: Cross-dehydrogenative C–O coupling of β-dicarbonyl compounds and their heteroanalogues with t-BuOOH....
Scheme 45: Oxidative C–O coupling of 2,6-dialkylphenyl-β-keto esters and thioesters with tert-butyl hydroxycar...
Scheme 46: α’-Acyloxylation of α,β-unsaturated ketones using KMnO4.
Scheme 47: Possible mechanisms of the acetoxylation at the allylic position of alkenes by Pd(OAc)2.
Scheme 48: Products of the oxidation of terminal alkenes by Pd(II)/AcOH/oxidant system.
Scheme 49: Acyloxylation of terminal alkenes with carboxylic acids.
Scheme 50: Synthesis of linear E-allyl esters by cross-dehydrogenative coupling of terminal alkenes wih carbox...
Scheme 51: Pd(OAc)2-catalyzed acetoxylation of Z-vinyl(triethylsilanes).
Scheme 52: α’-Acetoxylation of α-acetoxyalkenes with copper(II) chloride in acetic acid.
Scheme 53: Oxidative acyloxylation at the allylic position of alkenes and at the benzylic position of alkylare...
Scheme 54: Copper-catalyzed alkoxylation of methylheterocyclic compounds using di-tert-butylperoxide as oxidan...
Scheme 55: Oxidative C–O coupling of methylarenes with β-dicarbonyl compounds or phenols.
Scheme 56: Copper-catalyzed esterification of methylbenzenes with cyclic ethers and cycloalkanes.
Scheme 57: Oxidative C–O coupling of carboxylic acids with toluene catalyzed by Pd(OAc)2.
Scheme 58: Oxidative acyloxylation at the allylic position of alkenes with carboxylic acids using the Bu4NI/t-...
Scheme 59: Cross-dehydrogenative C–O coupling of carboxylic acids with alkylarenes using the Bu4NI/t-BuOOH sys...
Scheme 60: Oxidative C–O cross-coupling of methylarenes with ethyl or isopropylarenes.
Scheme 61: Phosphorylation of benzyl C–H bonds using the Bu4NI/t-BuOOH oxidative system.
Scheme 62: Selective C–H acetoxylation of 2,3-disubstituted indoles.
Scheme 63: Acetoxylation of benzylic position of alkylarenes using DDQ as oxidant.
Scheme 64: C–H acyloxylation of diarylmethanes, 3-phenyl-2-propen-1-yl acetate and dimethoxyarene using DDQ.
Scheme 65: Cross-dehydrogenative C–O coupling of 1,3-diarylpropylenes and 1,3-diarylpropynes with alcohols.
Scheme 66: One-pot azidation and C–H acyloxylation of 3-chloro-1-arylpropynes.
Scheme 67: Cross-dehydrogenative C–O coupling of 1,3-diarylpropylenes, (E)-1-phenyl-2-isopropylethylene and is...
Scheme 68: Cross-dehydrogenative C–O coupling of alkylarenes and related compounds with N-hydroxyphthalimide.
Scheme 69: Acetoxylation at the benzylic position of alkylarenes mediated by N-hydroxyphthalimide.
Scheme 70: C–O coupling of methylarenes with aromatic carboxylic acids employing the NaBrO3/NaHSO3 system.
Scheme 71: tert-Butyl peroxidation of allyl, propargyl and benzyl ethers catalyzed by Fe(acac)3.
Scheme 72: Cross-dehydrogenative C–O coupling of ethers with carboxylic acids mediated by Bu4NI/t-BuOOH system....
Scheme 73: Oxidative acyloxylation of dimethylamides and dioxane with 2-aryl-2-oxoacetic acids accompanied by ...
Scheme 74: tert-Butyl peroxidation of N-benzylamides and N-allylbenzamide using the Bu4NI/t-BuOOH system.
Scheme 75: Cross-dehydrogenative C–O coupling of aromatic carboxylic acids with ethers using Fe(acac)3 as cata...
Scheme 76: Cross-dehydrogenative C–O coupling of cyclic ethers with 2-hydroxybenzaldehydes using iron carbonyl...
Scheme 77: Cross-dehydrogenative C–O coupling of ethers with β-dicarbonyl compounds and phenols using copper c...
Scheme 78: Cross-dehydrogenative C–O coupling of 2-hydroxybenzaldehyde with dioxane catalyzed by Cu2(BPDC)2(BP...
Scheme 79: Ruthenium chloride-catalyzed acyloxylation of β-lactams.
Scheme 80: Ruthenium-catalyzed tert-butyl peroxydation amides and acetoxylation of β-lactams.
Scheme 81: PhI(OAc)2-mediated α,β-diacetoxylation of tertiary amines.
Scheme 82: Electrochemical oxidative methoxylation of tertiary amines.
Scheme 83: Cross-dehydrogenative C–O coupling of ketene dithioacetals with carboxylic acids in the presence of...
Scheme 84: Cross-dehydrogenative C–O coupling of enamides with carboxylic acids using iodosobenzene as oxidant....
Scheme 85: Oxidative alkoxylation, acetoxylation, and tosyloxylation of acylanilides using PhI(O(O)CCF3)2 in t...
Scheme 86: Proposed mechanism of the oxidative C–O coupling of actetanilide with O-nucleophiles in the presenc...
Scheme 87: Three-component coupling of aldehydes, anilines and alcohols involving oxidative intermolecular C–O...
Scheme 88: Oxidative coupling of phenols with alcohols.
Scheme 89: 2-Acyloxylation of quinoline N-oxides with arylaldehydes in the presence of the CuOTf/t-BuOOH syste...
Scheme 90: Cross-dehydrogenative C–O coupling of azoles with primary alcohols.
Scheme 91: Oxidation of dipyrroles to dipyrrins and subsequent oxidative alkoxylation in the presence of Na3Co...
Scheme 92: Oxidative dehydrogenative carboxylation of alkanes and cycloalkanes to allylic esters.
Scheme 93: Pd-catalyzed acetoxylation of benzene.
Recent advances in the electrochemical construction of heterocycles
- Robert Francke
Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303
- coupling. In addition to enol ethers 1, vinyl sulfides and ketene acetals have successfully been cyclized according to Scheme 2 [34][35][36]. An interesting modification of this anodic coupling method was achieved by Yoshida, Nokami and co-workers using the “cation pool” concept [37][38][39]. In this
- 24 [72]. In this example, 1,2-benzoquinone derivatives are generated in the presence of ketene N,O-acetals 70. Out of four possible regioisomers, 71a and 71b are exclusively formed (in ratios 71a/71b between 1:1 and 1:2). In a follow-up study, unreacted α-arylated ketene N,O-acetal intermediates (63
- , Scheme 24) have been identified as byproducts [73][74]. Furthermore, it was demonstrated that ketene N,S-acetals can also be employed for indole synthesis, although the use of these substrates is associated with lower yields compared to N,O-acetals [75]. 2.3 Acyl iminium ions and alkoxycarbenium ions in
Graphical Abstract
Figure 1: Common types of electrochemically induced cyclization reactions.
Scheme 1: Principle of indirect electrolysis.
Scheme 2: Anodic intramolecular cyclization of olefines in methanol.
Scheme 3: Anodic cyclization of olefines in CH2Cl2/DMSO.
Scheme 4: Intramolecular coupling of 1,6-dienes in CH2Cl2/DMSO.
Scheme 5: Cyclization of bromopropargyloxy ester 12.
Scheme 6: Proposed mechanism for the radical cyclization of bromopropargyloxy ester 12.
Scheme 7: Preparation of pyrrolidines and tetrahydrofurans via Kolbe-type electrolysis of unsaturated carboxy...
Scheme 8: Anodic cyclization of chalcone oximes 19.
Scheme 9: Generation of N-acyliminium (23) and alkoxycarbenium species (24) from amides and ethers with and w...
Scheme 10: Anodic cyclization of dipeptide 25.
Scheme 11: Anodic cyclization of a dipeptide using an electroauxiliary.
Scheme 12: Anodic cyclization of hydroxyamino compound 29.
Scheme 13: Cyclization of unsaturated thioacetals using the ArS(ArSSAr)+ mediator.
Scheme 14: Cyclization of biaryl 35 to carbazol 36 as key-step of the synthesis of glycozoline (37).
Scheme 15: Electrosynthesis of 39 as part of the total synthesis of alkaloids 40 and 41.
Scheme 16: Wacker-type cyclization of alkenyl phenols 42.
Scheme 17: Cathodic synthesis of indol derivatives.
Scheme 18: Fluoride mediated anodic cyclization of α-(phenylthio)acetamides.
Scheme 19: Synthesis of 2-substituted benzoxazoles from Schiff bases.
Scheme 20: Synthesis of euglobal model compounds via electrochemically induced Diels–Alder cycloaddition.
Scheme 21: Cycloaddition of anodically generated N-acyliminium species 58 with olefins and alkynes.
Scheme 22: Electrochemical aziridination of olefins.
Scheme 23: Proposed mechanism for the aziridination reaction.
Scheme 24: Electrochemical synthesis of benzofuran and indole derivatives.
Scheme 25: Anodic anellation of catechol derivatives 66 with different 1,3-dicarbonyl compounds.
Scheme 26: Electrosynthesis of 1,2-fused indoles from catechol and ketene N,O-acetals.
Scheme 27: Reaction of N-acyliminium pools with olefins having a nucleophilic substituent.
Scheme 28: Synthesis of thiochromans using the cation-pool method.
Scheme 29: Electrochemical synthesis and diversity-oriented modification of 73.
Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative
- Bernd Schmidt and
- Sylvia Hauke
Beilstein J. Org. Chem. 2014, 10, 1023–1031, doi:10.3762/bjoc.10.102
- dealkoxylation of acetals [65] and for desilylation reactions of silyl ethers [66]. With in situ generated Pd/C (obtained from Pd(OAc)2 and charcoal according to Felpin’s protocol) [67] an improved selectivity was observed as the cleavage of the silyl groups could be suppressed. However, reductive dealkoxylation
Graphical Abstract
Figure 1: Structures of kigamicin B and aclacinomycin A as representative examples for antineoplastic glycoco...
Scheme 1: RCM-isomerization approach to L-amicetal 4 and alternative CM approaches to L-amicetose.
Scheme 2: Two step desilylation–acetal hydrolysis.
Scheme 3: Deprotection of 11 and 12 to L-amicetose derivative 16.
Scheme 4: Synthesis of a cinerulose-TBS ether 22.
Scheme 5: Deprotection of 24.
