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Search for "titanium" in Full Text gives 113 result(s) in Beilstein Journal of Organic Chemistry.
On the mechanism of photocatalytic reactions with eosin Y
- Michal Majek,
- Fabiana Filace and
- Axel Jacobi von Wangelin
Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97
- with arenediazonium salts are often more selective than traditional methods such as copper(II)-mediated Meerwein arylations [11] or protocols employing stoichiometric iron(II) or titanium(III) reductants in aqueous media [12][13][14]. This renaissance of arene diazonium chemistry has recently led to
Graphical Abstract
Scheme 1: Oxidative quenching of eosin Y with arenediazonium salts and reactions of the resultant aryl radica...
Scheme 2: Proposed general reaction mechanism of eosin Y-catalyzed substitutions with arene diazonium salts.
Figure 1: UV–vis spectra of the photoborylation reaction mixture (RM).
Figure 2: Fluorescence spectra of the photoborylation reaction mixture (RM). Ex. = excitation wavelength.
Scheme 3: Acid–base behaviour of eosin Y.
Figure 3: UV–vis spectrum of p-bromobenzenediazonium tetrafluoroborate (pBrPhN2) and bispinacolato diboron (B2...
Scheme 4: Eosin Y-catalyzed and dye-free photolytic borylation.
Scheme 5: Eosin Y-catalyzed and dye-free reactions with ethyl propiolate.
Figure 4: UV–vis spectra of ortho-biphenyldiazonium tetrafluoroborate (biPhN2) in acetonitrile.
Scheme 6: Quantum yield determinations of selected visible-light-driven aromatic substitutions.
Synthesis of chiral N-phosphinyl α-imino esters and their application in asymmetric synthesis of α-amino esters by reduction
- Yiwen Xiong,
- Haibo Mei,
- Lingmin Wu,
- Jianlin Han,
- Yi Pan and
- Guigen Li
Beilstein J. Org. Chem. 2014, 10, 653–659, doi:10.3762/bjoc.10.57
- tetraisopropoxytitanium was used as condensing reagent (Table 1, entries 5–8). Further treatment with titanium tetrachloride/triethyl amine gave a positive result and 46% chemical yield was obtained (Table 1, entry 9). Then, further investigation revealed that the best yield (47%) was observed when the reaction was
Graphical Abstract
Figure 1: Typical sulfinyl (a), phosphonyl aldimines (b) and phosphinyl imino esters (c).
Scheme 1: Synthesis of α-imino ester by rearrangement.
Scheme 2: Cleavage of the chiral auxiliary.
Silica: An efficient catalyst for one-pot regioselective synthesis of dithioethers
- Samir Kundu,
- Babli Roy and
- Basudeb Basu
Beilstein J. Org. Chem. 2014, 10, 26–33, doi:10.3762/bjoc.10.5
- and also as spacers in metal-organic frameworks [9][10][11][12][13][14]. For example, vicinal dithioether-based zirconium and titanium complexes have been used for alkene polymerization and hydroamination [15][16][17][18]. Chiral dithioethers have been prepared and their iridium complexes have been
Graphical Abstract
Scheme 1: Sequential substitution-addition reactions of thiols with allyl halides leading to the formation of...
Scheme 2: Plausible mechanisms for the regioselective formation of vicinal and 1,3-dithioethers by using dry ...
Recent advances in transition metal-catalyzed Csp2-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation
- Grégory Landelle,
- Armen Panossian,
- Sergiy Pazenok,
- Jean-Pierre Vors and
- Frédéric R. Leroux
Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287
- iodide and generate the corresponding radical (Scheme 13). Titanium dioxide was used as heterogeneous photocatalyst in the perfluoroalkylation of α-methylstyrene with perfluorohexyl iodide by M. Yoshida et al. [120]. While the main product arose from the formal perfluoroalkylation of a methyl sp3-C–H
Graphical Abstract
Scheme 1: Pd-catalyzed monofluoromethylation of pinacol phenylboronate [44].
Scheme 2: Cu-catalyzed monofluoromethylation with 2-PySO2CHFCOR followed by desulfonylation [49].
Scheme 3: Cu-catalyzed difluoromethylation with α-silyldifluoroacetates [57].
Figure 1: Mechanism of the Cu-catalyzed C–CHF2 bond formation of α,β-unsaturated carboxylic acids through dec...
Scheme 4: Fe-catalyzed decarboxylative difluoromethylation of cinnamic acids [62].
Scheme 5: Preliminary experiments for investigation of the mechanism of the C–H trifluoromethylation of N-ary...
Figure 2: Plausible catalytic cycle proposed by Z.-J. Shi et al. for the trifluoromethylation of acetanilides ...
Figure 3: Plausible catalytic cycle proposed by M. S. Sanford et al. for the perfluoroalkylation of simple ar...
Figure 4: Postulated reaction pathway for the Ag/Cu-catalyzed trifluoromethylation of aryl iodides by Z. Q. W...
Figure 5: Postulated reaction mechanism for Cu-catalyzed trifluoromethylation reaction using MTFA as trifluor...
Scheme 6: Formal Heck-type trifluoromethylation of vinyl(het)arenes by M. Sodeoka et al. [83].
Figure 6: Proposed catalytic cycle for the copper-catalyzed trifluoromethylation of (het)arenes in presence o...
Figure 7: Proposed catalytic cycle for the copper-catalyzed trifluoromethylation of N,N-disubstituted (hetero...
Figure 8: Proposed catalytic cycle by Y. Zhang and J. Wang et al. for the copper-catalyzed trifluoromethylati...
Figure 9: Mechanistic rationale for the trifluoromethylation of arenes in presence of Langlois’s reagent and ...
Scheme 7: Trifluoromethylation of 4-acetylpyridine with Langlois’s reagent by P. S. Baran et al. (* Stirring ...
Scheme 8: Catalytic copper-facilitated perfluorobutylation of benzene with C4F9I and benzoyl peroxide [90].
Figure 10: F.-L. Qing et al.’s proposed mechanism for the copper-catalyzed trifluoromethylation of (hetero)are...
Figure 11: Mechanism of the Cu-catalyzed/Ru-photocatalyzed trifluoromethylation and perfluoroalkylation of ary...
Figure 12: Proposed mechanism for the Cu-catalyzed trifluoromethylation of aryl- and vinyl boronic acids with ...
Figure 13: Possible mechanism for the Cu-catalyzed decarboxylative trifluoromethylation of cinnamic acids [62].
Scheme 9: Ruthenium-catalyzed perfluoroalkylation of alkenes and (hetero)arenes with perfluoroalkylsulfonyl c...
Figure 14: N. Kamigata et al.’s proposed mechanism for the Ru-catalyzed perfluoroalkylation of alkenes and (he...
Figure 15: Proposed mechanism for the Ru-catalyzed photoredox trifluoromethylation of (hetero)arenes with trif...
Figure 16: Late-stage trifluoromethylation of pharmaceutically relevant molecules with trifluoromethanesulfony...
Figure 17: Proposed mechanism for the trifluoromethylation of alkenes with trifluoromethyl iodide under Ru-bas...
Scheme 10: Formal perfluoroakylation of terminal alkenes by Ru-catalyzed cross-metathesis with perfluoroalkyle...
Figure 18: One-pot Ir-catalyzed borylation/Cu-catalyzed trifluoromethylation of complex small molecules by Q. ...
Figure 19: Mechanistic proposal for the Ni-catalyzed perfluoroalkylation of arenes and heteroarenes with perfl...
Scheme 11: Electrochemical Ni-catalyzed perfluoroalkylation of 2-phenylpyridine (Y. H. Budnikova et al.) [71].
Scheme 12: Fe(II)-catalyzed trifluoromethylation of arenes and heteroarenes with trifluoromethyl iodide (T. Ya...
Figure 20: Mechanistic proposal by T. Yamakawa et al. for the Fe(II)-catalyzed trifluoromethylation of arenes ...
Scheme 13: Ytterbium-catalyzed perfluoroalkylation of dihydropyran with perfluoroalkyl iodide (Y. Ding et al.) ...
Figure 21: Mechanistic proposal by A. Togni et al. for the rhenium-catalyzed trifluoromethylation of arenes an...
Figure 22: Mechanism of the Cu-catalyzed oxidative trifluoromethylthiolation of arylboronic acids with TMSCF3 ...
Scheme 14: Removal of the 8-aminoquinoline auxiliary [136].
Figure 23: Mechanism of the Cu-catalyzed trifluoromethylthiolation of C–H bonds with a trifluoromethanesulfony...
An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles
- Marcus Baumann and
- Ian R. Baxendale
Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265
- -picoline can be readily oxidised via another gas-phase protocol using a fixed-bed reactor charged with vanadium pentoxide on high surface titanium dioxide (5–50 wt % vanadium). A modification of the sequence utilises a dehydrative amminolysis (ammoxidation) to furnish the corresponding 3-cyanopyridine
Graphical Abstract
Scheme 1: Scaled industrial processes for the synthesis of simple pyridines.
Scheme 2: Synthesis of nicotinic acid from 2-methyl-5-ethylpyridine (1.11).
Scheme 3: Synthesis of 3-picoline and nicotinic acid.
Scheme 4: Synthesis of 3-picoline from 2-methylglutarodinitrile 1.19.
Scheme 5: Picoline-based synthesis of clarinex (no yields reported).
Scheme 6: Mode of action of proton-pump inhibitors and structures of the API’s.
Scheme 7: Hantzsch-like route towards the pyridine rings in common proton pump inhibitors.
Figure 1: Structures of rosiglitazone (1.40) and pioglitazone (1.41).
Scheme 8: Synthesis of rosiglitazone.
Scheme 9: Syntheses of 2-pyridones.
Scheme 10: Synthesis and mechanism of 2-pyrone from malic acid.
Scheme 11: Polymer-assisted synthesis of rosiglitazone.
Scheme 12: Synthesis of pioglitazone.
Scheme 13: Meerwein arylation reaction towards pioglitazone.
Scheme 14: Route towards pioglitazone utilising tyrosine.
Scheme 15: Route towards pioglitazone via Darzens ester formation.
Scheme 16: Syntheses of the thiazolidinedione moiety.
Scheme 17: Synthesis of etoricoxib utilising Negishi and Stille cross-coupling reactions.
Scheme 18: Synthesis of etoricoxib via vinamidinium condensation.
Figure 2: Structures of nalidixic acid, levofloxacin and moxifloxacin.
Scheme 19: Synthesis of moxifloxacin.
Scheme 20: Synthesis of (S,S)-2,8-diazabicyclo[4.3.0]nonane 1.105.
Scheme 21: Synthesis of levofloxacin.
Scheme 22: Alternative approach to the levofloxacin core 1.125.
Figure 3: Structures of nifedipine, amlodipine and clevidipine.
Scheme 23: Mg3N2-mediated synthesis of nifedipine.
Scheme 24: Synthesis of rac-amlodipine as besylate salt.
Scheme 25: Aza Diels–Alder approach towards amlodipine.
Scheme 26: Routes towards clevidipine.
Figure 4: Examples of piperidine containing drugs.
Figure 5: Discovery of tiagabine based on early leads.
Scheme 27: Synthetic sequences to tiagabine.
Figure 6: Structures of solifenacin (2.57) and muscarine (2.58).
Scheme 28: Enantioselective synthesis of solifenacin.
Figure 7: Structures of DPP-4 inhibitors of the gliptin-type.
Scheme 29: Formation of inactive diketopiperazines from cis-rotameric precursors.
Figure 8: Co-crystal structure of carmegliptin bound in the human DPP-4 active site (PDB 3kwf).
Scheme 30: Improved route to carmegliptin.
Figure 9: Structures of lamivudine and zidovudine.
Scheme 31: Typical routes accessing uracil, thymine and cytosine.
Scheme 32: Coupling between pyrimidones and riboses via the Vorbrüggen nucleosidation.
Scheme 33: Synthesis of lamivudine.
Scheme 34: Synthesis of raltegravir.
Scheme 35: Mechanistic studies on the formation of 3.22.
Figure 10: Structures of selected pyrimidine containing drugs.
Scheme 36: General preparation of pyrimidines and dihydropyrimidones.
Scheme 37: Synthesis of imatinib.
Scheme 38: Flow synthesis of imatinib.
Scheme 39: Syntheses of erlotinib.
Scheme 40: Synthesis of erlotinib proceeding via Dimroth rearrangement.
Scheme 41: Synthesis of lapatinib.
Scheme 42: Synthesis of rosuvastatin.
Scheme 43: Alternative preparation of the key aldehyde towards rosuvastatin.
Figure 11: Structure comparison between nicotinic acetylcholine receptor agonists.
Scheme 44: Syntheses of varenicline and its key building block 4.5.
Scheme 45: Synthetic access to eszopiclone and brimonidine via quinoxaline intermediates.
Figure 12: Bortezomib bound in an active site of the yeast 20S proteasome ([114], pdb 2F16).
Scheme 46: Asymmetric synthesis of bortezomib.
Figure 13: Structures of some prominent piperazine containing drugs.
Figure 14: Structural comparison between the core of aplaviroc (4.35) and a type-1 β-turn (4.36).
Scheme 47: Examplary synthesis of an aplaviroc analogue via the Ugi-MCR.
Scheme 48: Syntheses of azelastine (5.1).
Figure 15: Structures of captopril, enalapril and cilazapril.
Scheme 49: Synthesis of cilazapril.
Figure 16: Structures of lamotrigine, ceftriaxone and azapropazone.
Scheme 50: Synthesis of lamotrigine.
Scheme 51: Alternative synthesis of lamotrigine (no yields reported).
Figure 17: Structural comparison between imiquimod and the related adenosine nucleoside.
Scheme 52: Conventional synthesis of imiquimod (no yields reported).
Scheme 53: Synthesis of imiquimod.
Scheme 54: Synthesis of imiquimod via tetrazole formation (not all yields reported).
Figure 18: Structures of various anti HIV-medications.
Scheme 55: Synthesis of abacavir.
Figure 19: Structures of diazepam compared to modern replacements.
Scheme 56: Synthesis of ocinaplon.
Scheme 57: Access to zaleplon and indiplon.
Scheme 58: Different routes towards the required N-methylpyrazole 6.65 of sildenafil.
Scheme 59: Polymer-supported reagents in the synthesis of key aminopyrazole 6.72.
Scheme 60: Early synthetic route to sildenafil.
Scheme 61: Convergent preparations of sildenafil.
Figure 20: Comparison of the structures of sildenafil, tadalafil and vardenafil.
Scheme 62: Short route to imidazotriazinones.
Scheme 63: Alternative route towards vardenafils core imidazotriazinone (6.95).
Scheme 64: Bayer’s approach to the vardenafil core.
Scheme 65: Large scale synthesis of vardenafil.
Scheme 66: Mode of action of temozolomide (6.105) as methylating agent.
Scheme 67: Different routes to temozolomide.
Scheme 68: Safer route towards temozolomide.
Figure 21: Some unreported heterocyclic scaffolds in top market drugs.
A reductive coupling strategy towards ripostatin A
- Kristin D. Schleicher and
- Timothy F. Jamison
Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175
- titanium-mediated, alkoxide-directed fragment coupling reaction between vinylcylopropanes and vinyldimethylchlorosilane (Scheme 3, reaction 4) in which the stereochemical outcome of the rearrangement is orchestrated by the adjacent alkoxide, which is believed to direct formation of a tricyclic
Graphical Abstract
Figure 1: Structures of the ripostatins.
Figure 2: Retrosynthesis of ripostatin A.
Scheme 1: Nickel-catalyzed reductive coupling of alkynes and epoxides.
Figure 3: Proposed retrosynthesis of ripostatin A featuring enyne–epoxide reductive coupling and rearrangemen...
Scheme 2: Potential transition states and stereochemical outcomes for a concerted 1,5-hydrogen rearrangement.
Scheme 3: Rearrangements of vinylcyclopropanes to acylic 1,4-dienes.
Scheme 4: Synthesis of cyclopropyl enyne.
Scheme 5: Synthesis of model epoxide for investigation of the nickel-catalyzed coupling reaction.
Scheme 6: Nickel-catalyzed enyne–epoxide reductive coupling reaction.
Scheme 7: Proposed mechanism for the nickel-catalyzed coupling reaction of alkynes or enynes with epoxides.
Scheme 8: Regioselectivity changes in reductive couplings of alkynes and 3-oxygenated epoxides.
Scheme 9: Enyne reductive coupling with 1,2-epoxyoctane.
Figure 4: Initial retrosynthesis of the epoxide fragment by using dithiane coupling.
Scheme 10: Synthesis of dithiane by Claisen rearrangement.
Scheme 11: Deuterium labeling reveals that the allylic/benzylic site is most acidic.
Scheme 12: Oxy-Michael addition to δ-hydroxy-α,β-enones.
Figure 5: Revised retrosynthesis of epoxide 5.
Scheme 13: Synthesis of functionalized ketone by oxy-Michael addition.
Figure 6: Retrosynthesis by using iodocylization to introduce the epoxide.
Scheme 14: Synthesis of ketone 57 using thiazolidinethione chiral auxiliary.
Figure 7: Retrosynthesis involving decarboxylation of a β-ketoester.
Scheme 15: Synthesis of β-ketoester 61.
Scheme 16: Decarboxylation of 61 under Krapcho conditions.
Scheme 17: Improved synthesis of 63 and attempted iodocyclization.
Figure 8: Retrosynthesis utilizing Rychnovsky’s cyanohydrin acetonide methodology.
Scheme 18: Synthesis of cyanohydrin acetonide and attempted alkylation with epoxide.
Scheme 19: Allylation of acetonide and conversion to aldehyde.
Scheme 20: Synthesis of the epoxide precursor by an aldol−decarboxylation sequence.
Homolytic substitution at phosphorus for C–P bond formation in organic synthesis
- Hideki Yorimitsu
Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143
- titanium complex (Scheme 23) [49]. This represents a unique direct method for preparing triorganophosphine without recourse to any trivalent phosphorus sources such as PCl3. Conclusion Introduction of a phosphorus atom by a radical process has offered an intriguing tool for the synthesis of
Graphical Abstract
Scheme 1: Representative C–P bond-forming reactions.
Scheme 2: General equation of homolytic substitution.
Scheme 3: Addition of diphenyl(triphenylstannyl)phosphine.
Scheme 4: Addition of diphenyl(trimethylstannyl)phosphine.
Scheme 5: Plausible mechanism of addition of R3Sn–PPh2.
Scheme 6: Addition of tetraorganodiphosphines to phenylacetylene.
Scheme 7: Plausible mechanism of anti-diphosphination.
Scheme 8: Radical diphosphination for synthesizing fluorescent material.
Scheme 9: Mechanism of thiophosphination with diphenyl(organosulfanyl)phosphine.
Scheme 10: Thiophosphination with S-thiophosphinyl O-ethyl dithiocarbonate.
Scheme 11: Photoinduced selenophosphination of allenes.
Scheme 12: Photoinduced tellurophosphination.
Scheme 13: Decarboxylative phosphorylation of carboxylic acid derivatives.
Scheme 14: Plausible mechanism of decarboxylative phosphorylation.
Scheme 15: Radical phosphination of PTOC esters with white phosphorus.
Scheme 16: Plausible mechanism of radical phosphination (Si = (Me3Si)3Si).
Scheme 17: Stereoselective phosphination leading to (S,S)-aminophosphine derivative.
Figure 1: Calculated reaction profile of homolytic substitution between Ph• and Me3Sn–PPh2 at the B2-PLYP-D/T...
Scheme 18: Phosphination with retention of axial chirality.
Scheme 19: Chemodivergent phosphination.
Scheme 20: Bis(phosphoryl)-bridged biphenyls by radical phosphination.
Scheme 21: Bis(phosphoryl)-bridged ladder triphenylene by radical phosphination.
Scheme 22: Photoinduced phosphination of perfluoroalkyl iodides with tetraphenyldiphosphine.
Scheme 23: Ti(III)-mediated radical phosphination of organic bromides with white phosphorus.
Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors
- Rahat Javaid,
- Shin-ichiro Kawasaki,
- Akira Suzuki and
- Toshishige M. Suzuki
Beilstein J. Org. Chem. 2013, 9, 1156–1163, doi:10.3762/bjoc.9.129
- acid (HNO3, 60%) and hydrogen peroxide (H2O2, 30%) were purchased from Wako Pure Chemical Industries Ltd. and were used without further purification. Fabrication of tubular reactors A double-layered tube (o.d. 1.6 mm, i.d. 0.5 mm, length 100 cm) composed of Inconel 625 and titanium (Ti) inner layer
- (thickness 120 μm) was fabricated by E.S.Q. Co., Japan, by elongation of the titanium inlaid Inconel 625 piece by stretch-draw process, and used as the reactor support [11]. The Ti inner surface was oxidized to TiO2 with H2O2 under supercritical water conditions (450 °C, 30 MPa). The TiO2 surface, which is
Graphical Abstract
Figure 1: (a) Graphical presentation of Pd–Ag co-plating and sequential removal of Ag to give a porous Pd sur...
Figure 2: Schematic diagram of experimental setup used for the catalytic hydrogenation of p-nitrophenol.
Scheme 1: Hydrogenation of p-nitrophenol with formic acid.
Figure 3: Influence of temperature on the conversion of 0.01 M p-nitrophenol with 0.1 M formic acid at 30 °C ...
Figure 4: Effect of residence time on the conversion of 0.01 M p-nitrophenol with 0.1 M formic acid at 30 °C ...
Figure 5: Effect of the concentration of formic acid on the conversion of 0.01 M p-nitrophenol. The formic ac...
Figure 6: Effect of pH on the conversion of 0.01 M p-nitrophenol by using 0.05 M formic acid. The porous PdO ...
Figure 7: Long-term testing for continuous hydrogenation of 0.01 M p-nitrophenol with 0.05 M formic acid in t...
Titanium-mediated reductive cross-coupling reactions of imines with terminal alkynes: An efficient route for the synthesis of stereodefined allylic amines
- Kebin Mao,
- Guoqin Fan,
- Yuanhong Liu,
- Shi Li,
- Xu You and
- Dan Liu
Beilstein J. Org. Chem. 2013, 9, 621–627, doi:10.3762/bjoc.9.69
- Chemical Technology, Shenyang 110142, People’s Republic of China 10.3762/bjoc.9.69 Abstract Low-valency titanium species, generated in situ by using Ti(OiPr)4/2 c-C5H9MgCl reagent, react with imines to give a titanium-imine complex that can couple with terminal alkynes to provide azatitanacyclopentenes
- undergoes an unexpected 1,3-amino migration on silica gel during the column chromatography. Keywords: allylic amine; azatitanacyclopentene; reductive cross-coupling; regioselectivity; terminal alkyne; titanium-imine complex; Introduction Allylic amines are fundamental three-carbon building blocks in
- alkynes produced an inseparable mixture of two regioisomers in some cases [33] or could not give the desired products [34]. Sato et al. reported that a divalent titanium reagent generated by the Ti(OiPr)4/2 iPrMgX system reacted with arylaldimines to provide the corresponding (η2-imine)Ti(OiPr)2 complex
Graphical Abstract
Scheme 1: Titanium-mediated cross-coupling of imines with terminal alkynes.
Scheme 2: Synthesis of allylic amine 5a by titanium-mediated coupling reaction of imine 2a with 1-heptyne.
Scheme 3: The regiochemistry of titanium-mediated cross-coupling of imine with terminal alkyne.
Figure 1: X-ray crystal structure of compound 5c.
Scheme 4: Synthesis of allylic amines 5q and 6q.
Figure 2: X-ray crystal structure of compound 8.
Scheme 5: Synthesis of allylic amine 9 by iodonolysis of azatitanacyclopentene 4g.
Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation
- Kei Murakami and
- Hideki Yorimitsu
Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34
- ]. As a result, Hoveyda’s zirconium-catalyzed reactions provided homobenzylmagnesium intermediates 4j, while Kambe’s titanium-catalyzed reactions afforded benzylmagnesium intermediates 4k. Kambe applied the titanocene-catalyzed reaction to a three-component coupling reaction involving a radical
- titanium-catalyzed allylmagnesiation of isoprene was reported in the 1970s, the scope of the reagents was limited to the allylic magnesium reagents [145][146]. Recently, Terao and Kambe reported copper-catalyzed regioselective carbomagnesiation of dienes and enynes using sec- or tert-alkylmagnesium
- . Zirconium-catalyzed alkylmagnesiation. Titanium-catalyzed carbomagnesiation. Three-component coupling reaction. Iron-catalyzed arylzincation reaction of oxabicyclic alkenes. Reaction of allenyl ketones with organomagnesium reagent. Regio- and stereoselective reaction of a 2,3-allenoate. Three-component
Graphical Abstract
Scheme 1: Variation of substrates for carbomagnesiation and carbozincation in this article.
Scheme 2: Copper-catalyzed arylmagnesiation and allylmagnesiation of alkynyl sulfone.
Scheme 3: Copper-catalyzed four-component reaction of alkynyl sulfoxide with alkylzinc reagent, diiodomethane...
Scheme 4: Rhodium-catalyzed reaction of aryl alkynyl ketones with arylzinc reagents.
Scheme 5: Allylmagnesiation of propargyl alcohol, which provides the anti-addition product.
Scheme 6: Negishi’s total synthesis of (Z)-γ-bisabolene by allylmagnesiation.
Scheme 7: Iron-catalyzed syn-carbomagnesiation of propargylic or homopropargylic alcohol.
Scheme 8: Mechanism of iron-catalyzed carbomagnesiation.
Scheme 9: Regio- and stereoselective manganese-catalyzed allylmagnesiation.
Scheme 10: Vinylation and alkylation of arylacetylene-bearing hydroxy group.
Scheme 11: Arylmagnesiation of (2-pyridyl)silyl-substituted alkynes.
Scheme 12: Synthesis of tamoxifen from 2g.
Scheme 13: Controlling regioselectivity of carbocupration by attaching directing groups.
Scheme 14: Rhodium-catalyzed carbozincation of ynamides.
Scheme 15: Synthesis of 4-pentenenitriles through carbometalation followed by aza-Claisen rearrangement.
Scheme 16: Uncatalyzed carbomagnesiation of cyclopropenes.
Scheme 17: Iron-catalyzed carbometalation of cyclopropenes.
Scheme 18: Enantioselective carbozincation of cyclopropenes.
Scheme 19: Copper-catalyzed facially selective carbomagnesiation.
Scheme 20: Arylmagnesiation of cyclopropenes.
Scheme 21: Enantioselective methylmagnesiation of cyclopropenes without catalyst.
Scheme 22: Copper-catalyzed carbozincation.
Scheme 23: Enantioselective ethylzincation of cyclopropenes.
Scheme 24: Nickel-catalyzed ring-opening aryl- and alkenylmagnesiation of a methylenecyclopropane.
Scheme 25: Reaction mechanism.
Scheme 26: Nickel-catalyzed carbomagnesiation of arylacetylene and dialkylacetylene.
Scheme 27: Nickel-catalyzed carbozincation of arylacetylenes and its application to the synthesis of tamoxifen....
Scheme 28: Bristol-Myers Squibb’s nickel-catalyzed phenylzincation.
Scheme 29: Iron/NHC-catalyzed arylmagnesiation of aryl(alkyl)acetylene.
Scheme 30: Iron/copper-cocatalyzed alkylmagnesiation of aryl(alkyl)acetylenes.
Scheme 31: Iron-catalyzed hydrometalation.
Scheme 32: Iron/copper-cocatalyzed arylmagnesiation of dialkylacetylenes.
Scheme 33: Chromium-catalyzed arylmagnesiation of alkynes.
Scheme 34: Cobalt-catalyzed arylzincation of alkynes.
Scheme 35: Cobalt-catalyzed formation of arylzinc reagents and subsequent arylzincation of alkynes.
Scheme 36: Cobalt-catalyzed benzylzincation of dialkylacetylene and aryl(alkyl)acetylenes.
Scheme 37: Synthesis of estrogen receptor antagonist.
Scheme 38: Cobalt-catalyzed allylzincation of aryl-substituted alkynes.
Scheme 39: Silver-catalyzed alkylmagnesiation of terminal alkyne.
Scheme 40: Proposed mechanism of silver-catalyzed alkylmagnesiation.
Scheme 41: Zirconium-catalyzed ethylzincation of terminal alkenes.
Scheme 42: Zirconium-catalyzed alkylmagnesiation.
Scheme 43: Titanium-catalyzed carbomagnesiation.
Scheme 44: Three-component coupling reaction.
Scheme 45: Iron-catalyzed arylzincation reaction of oxabicyclic alkenes.
Scheme 46: Reaction of allenyl ketones with organomagnesium reagent.
Scheme 47: Regio- and stereoselective reaction of a 2,3-allenoate.
Scheme 48: Three-component coupling reaction of 1,2-allenoate, organozinc reagent, and ketone.
Scheme 49: Proposed mechanism for a rhodium-catalyzed arylzincation of allenes.
Scheme 50: Synthesis of skipped polyenes by iterative arylzincation/allenylation reaction.
Scheme 51: Synthesis of 1,4-diorganomagnesium compound from 1,2-dienes.
Scheme 52: Synthesis of tricyclic compounds.
Scheme 53: Manganese-catalyzed allylmagnesiation of allenes.
Scheme 54: Copper-catalyzed alkylmagnesiation of 1,3-dienes and 1,3-enynes.
Scheme 55: Chromium-catalyzed methallylmagnesiation of 1,6-diynes.
Scheme 56: Chromium-catalyzed allylmagnesiation of 1,6-enynes.
Scheme 57: Proposed mechanism of the chromium-catalyzed methallylmagnesiation.
Towards a biocompatible artificial lung: Covalent functionalization of poly(4-methylpent-1-ene) (TPX) with cRGD pentapeptide
- Lena Möller,
- Christian Hess,
- Jiří Paleček,
- Yi Su,
- Axel Haverich,
- Andreas Kirschning and
- Gerald Dräger
Beilstein J. Org. Chem. 2013, 9, 270–277, doi:10.3762/bjoc.9.33
- by the Lahann group [35]. We believe that the copper-free approach described is of general importance and should be transferrable to (bio)polymers, inorganic materials or to metals such as titanium used in biomedical devices [36]. Schematic presentation of the artificial lung (A) and concept of
Graphical Abstract
Figure 1: Schematic presentation of the artificial lung (A) and concept of membrane functionalization (B) wit...
Scheme 1: Functionalization of poly(4-methylpent-1-ene) (TPX) 2.
Figure 2: Analyses of functionalized TPX membranes with UV light at 312 nm; left: derivative 4; right: nonfun...
Figure 3: Analyses of functionalized TPX 4 by XPS spectroscopy using hν = 1250 eV; (a) overview, (b) F 1s cor...
Scheme 2: Copper-catalyzed and copper-free azide–alkyne “click“ reaction between functionalized TPX membranes ...
Figure 4: UV spectra of TPX 8c and 8d functionalized with fluorescein revealing the efficiency of the 1,3-dip...
Figure 5: Cell seeding onto TPX derivatives (scale bar equals 500 µm) (a) 2 as control with heparin/albumin d...
Intramolecular carbolithiation of N-allyl-ynamides: an efficient entry to 1,4-dihydropyridines and pyridines – application to a formal synthesis of sarizotan
- Wafa Gati,
- Mohamed M. Rammah,
- Mohamed B. Rammah and
- Gwilherm Evano
Beilstein J. Org. Chem. 2012, 8, 2214–2222, doi:10.3762/bjoc.8.250
- the carbometallation of various carbon–carbon multiple bonds. Lithium, copper, zinc, magnesium, zirconium, titanium, palladium and other metals are suitable for this transformation and considerable progress has recently been made in this area. Among these systems, the carbometallation of alkynes
Graphical Abstract
Scheme 1: Strategy for the synthesis of (1,4-dihydro)pyridines by deprotonation/intramolecular carbolithiatio...
Scheme 2: Feasibility of the deprotonation/intramolecular carbolithiation.
Scheme 3: Synthesis of the starting N-allyl-ynamides.
Scheme 4: Intramolecular carbolithiation of N-allyl-ynamides to 1,4-dihydropyridines and pyridines.
Scheme 5: 2,3-Disubstituted pyridines by trapping of the intermediate metallated 1,4-dihydropyridine.
Scheme 6: Formal synthesis of the anti-dyskinesia agent, 5-HT1A receptor agonist, dopamine D2 receptor ligand...
Flow photochemistry: Old light through new windows
- Jonathan P. Knowles,
- Luke D. Elliott and
- Kevin I. Booker-Milburn
Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229
- efficient irradiation of the whole reaction media; this is especially useful if the photocatalyst is solid supported. The immobilised catalyst of choice is titanium dioxide, both with and without Pt doping, due to its photochemical stability. The photocatalyst can be effectively deposited onto a
- [44], perchloroethylene [45] and 4-chlorophenol [46], mainly with a view to air and water purification [47]. The following section will focus only on synthetic applications of such reactors. Photoexcitation of titanium dioxide semiconductors leads to the promotion of an electron to the conduction band
- , leaving behind a positive hole in the valence band. Thus titanium dioxide can function either as an oxidant by donation of an electron of a reacting molecule into an electron hole, or as a reductant by the donation of an electron in the conduction band of titanium dioxide to another molecule. One
Graphical Abstract
Figure 1: An immersion-well batch reactor with 125 W medium pressure Hg lamp.
Figure 2: Transmission profile of a 0.05 M solution, ε = 200 M−1 cm−1.
Figure 3: Schematic of a typical microflow photochemical reactor (above) and detail of a triple-channel micro...
Figure 4: Schematic of a typical macroflow photochemical reactor (above) and images of the FEP photochemical ...
Scheme 1: [2 + 2] photocycloadditions of enones with enol derivatives.
Scheme 2: Competing reactions in an intramolecular [2 + 2] photocycloaddition.
Scheme 3: Diastereocontrolled cycloaddition of a cyclic enone with cyclopentene.
Scheme 4: Comparison of yields and reaction times for a batch reactor with a microflow system.
Scheme 5: Intramolecular [2 + 2] photocycloaddition.
Scheme 6: Paterno–Büchi reaction of benzophenone with an allylic alcohol.
Scheme 7: Photooxygenation of cyclopentadiene.
Scheme 8: Preparation of the anthelmintic ascaridole 23.
Scheme 9: Production of rose oxide 27 from (−)-β-citronellol (24).
Scheme 10: Photocatalytic alkylation of benzylamine.
Scheme 11: Photocatalytic reduction of 4-nitroacetophenone.
Scheme 12: Conversion of L-lysine to L-pipecolinic acid.
Scheme 13: Photocatalytic hydrodehalogenation.
Scheme 14: Photocatalytic aza-Henry reactions.
Scheme 15: Photocatalytic α-alkylation of aliphatic ketones.
Scheme 16: Decarboxylative photochemical additions.
Scheme 17: Photochemical addition of isopropanol to furanones.
Scheme 18: Photochemical addition of methanol to limonene.
Scheme 19: Light-promoted reduction of flavone.
Scheme 20: Photoreduction of benzophenone with benzhydrol.
Scheme 21: Barton reaction in a microflow system.
Scheme 22: Microflow synthesis of vitamin D3.
Scheme 23: photochemical chlorination of cyclohexane.
Scheme 24: photochemical cyanation of pyrene.
Scheme 25: Intermolecular [2 + 2] cycloaddition of maleimide (76) and intramolecular [2 + 2] cycloaddition of ...
Scheme 26: Intramolecular [5 + 2] cycloaddition of maleimide under flow conditions.
Scheme 27: Intramolecular [5 + 2] cycloaddition as a key step in the synthesis of (±)-neostenine.
Scheme 28: In situ generation of a thioaldehyde by photolysis of a phenacyl sulfide.
Scheme 29: Photodimerisation of maleic anhydride.
Scheme 30: [2 + 2] cycloaddition of a chiral enone with ethylene.
Scheme 31: Intramolecular [2 + 2] cycloaddition of a cyclopentenone.
Scheme 32: Photochemical Wolff rearrangement and cyclisation to β-lactams.
Scheme 33: Photochemical rearrangement of aryl azides.
Scheme 34: Rearrangement of quinoline N-oxides to quinolones.
Scheme 35: Photochemical rearrangement of cyclobutenones.
Scheme 36: Photoisomerisation en route to a vitamin-D derivative.
Scheme 37: Schematic of the Seeberger photooxygenation apparatus and sensitised photooxygenation of citronello...
Scheme 38: Sensitised photooxygenation of dihydroartemisinic acid.
Scheme 39: Photochemical preparation of CpRu(MeCN)3PF6.
Scheme 40: In situ photochemical generation and reaction of a [CpRu]+ catalyst.
Scheme 41: Intermolecular alkene–alkyne coupling with photogenerated catalyst.
Scheme 42: PET deoxygenation of nucleosides.
Scheme 43: Photochemical defluorination of DABFT.
Scheme 44: Aromatic azide reduction by visible-light-mediated photocatalysis.
Scheme 45: Examples of visible-light-mediated reactions.
Scheme 46: Visible-light-mediated formation of iminium ions.
Scheme 47: Examples of visible-light-mediated photocatalytic reactions.
Scheme 48: Anhydride formation from a visible-light-mediated process.
Scheme 49: Light-mediated conjugate addition of glycosyl bromide 141 to acrolein.
Scheme 50: Visible-light-mediated photocyclisation to [5]helicene.
The chemistry of bisallenes
- Henning Hopf and
- Georgios Markopoulos
Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225
Graphical Abstract
Figure 1: Loschmidt’s structure proposal for benzene (1) (Scheme 181 from [3]) and the corresponding modern stru...
Figure 2: The first isolated bisallenes.
Figure 3: Carbon skeletons of selected bisallenes discussed in this review.
Scheme 1: The preparation of 1,2,4,5-hexatetraene (2).
Scheme 2: The preparation of a conjugated bisallene by the DMS-protocol.
Scheme 3: Preparation of the 3-deuterio- and 3,4-dideuterio derivatives of 24.
Scheme 4: A versatile method to prepare alkylated conjugated bisallenes and other allenes.
Scheme 5: A preparation of 3,4-dimethyl-1,2,4,5-hexatetraene (38).
Scheme 6: A (C6 + 0)-approach to 1,2,4,5-hexatetraene (2).
Scheme 7: The preparation of a fully alkylated bisallenes from a 2,4-hexadiyne-1,6-diol diacetate.
Scheme 8: The preparation of the first phenyl-substituted conjugated bisallenes 3 and 4.
Scheme 9: Selective hydrogenation of [5]cumulenes to conjugated bisallenes: another (C6 + 0)-route.
Scheme 10: Aryl-substituted conjugated bisallenes by a (C3 + C3)-approach.
Scheme 11: Hexaphenyl-1,2,4,5-hexatetraene (59) by a (C3 + C3)-approach.
Scheme 12: An allenation route to conjugated bisallenes.
Scheme 13: The preparation of 3,4-difunctionalized conjugated bisallenes.
Scheme 14: Problems during the preparation of sulfur-substituted conjugated bisallenes.
Scheme 15: The preparation of 3,4-dibromo bisallenes.
Scheme 16: Generation of allenolates by an oxy-Cope rearrangement.
Scheme 17: A linear trimerization of alkynes to conjugated bisallenes: a (C2 + C2 + C2)-protocol.
Scheme 18: Preparation of a TMS-substituted conjugated bisallene by a C3-dimerization route.
Scheme 19: A bis(trimethylsilyl)bisallene by a C3-coupling protocol.
Scheme 20: The rearrangement of highly substituted benzene derivatives into their conjugated bisallenic isomer...
Scheme 21: From fully substituted benzene derivatives to fully substituted bisallenes.
Scheme 22: From a bicyclopropenyl to a conjugated bisallene derivative.
Scheme 23: The conversion of a bismethylenecyclobutene into a conjugated bisallene.
Scheme 24: The preparation of monofunctionalized bisallenes.
Scheme 25: Preparation of bisallene diols and their cyclization to dihydrofurans.
Scheme 26: A 3,4-difunctionalized conjugated bisallene by a C3-coupling process.
Scheme 27: Preparation of a bisallenic diketone by a coupling reaction.
Scheme 28: Sulfur and selenium-substituted bisallenes by a [2.3]sigmatropic rearrangement.
Scheme 29: The biallenylation of azetidinones.
Scheme 30: The preparation of a fully ferrocenylated conjugated bisallene.
Scheme 31: The first isomerization of a 1,5-hexadiyne to a 1,2,4,5-hexatetraene.
Scheme 32: The preparation of alkynyl-substituted bisallenes by a C3-dimerization protocol.
Scheme 33: Preparation of another completely ferrocenylated bisallene.
Scheme 34: The cyclization of 1,5-hexadiyne (129) to 3,4-bismethylenecyclobutene (130) via 1,2,4,5-hexatetraen...
Scheme 35: Stereochemistry of the thermal cyclization of bisallenes to bismethylenecyclobutenes.
Scheme 36: Bisallene→bismethylenecyclobutene ring closures in the solid state.
Scheme 37: A bisallene cyclization/dimerization reaction.
Scheme 38: A selection of Diels–Alder additions of 1,2,4,5-hexatetraene with various double-bond dienophiles.
Scheme 39: The stereochemistry of the [2 + 4] cycloaddition to conjugated bisallenes.
Scheme 40: Preparation of azetidinone derivatives from conjugated bisallenes.
Scheme 41: Cycloaddition of heterodienophiles to a conjugated bisallene.
Scheme 42: Addition of triple-bond dienophiles to conjugated bisallenes.
Scheme 43: Sulfur dioxide addition to conjugated bisallenes.
Scheme 44: The addition of a germylene to a conjugated bisallene.
Scheme 45: Trapping of conjugated bisallenes with phosphinidenes.
Scheme 46: The cyclopropanantion of 1,2,4,5-hexatetraene (2).
Scheme 47: Photochemical reactions involving conjugated bisallenes.
Scheme 48: Base-catalyzed isomerizations of conjugated bisallenes.
Scheme 49: Ionic additions to a conjugated bisallene.
Scheme 50: Oxidation reactions of a conjugated bisallene.
Scheme 51: The mechanism of oxidation of the bisallene 24.
Scheme 52: CuCl-catalyzed cyclization of 1,2,4,5-hexatetraene (2).
Scheme 53: The conversion of conjugated bisallenes into cyclopentenones.
Scheme 54: Oligomerization of a conjugated bisallene by nickel catalysts.
Scheme 55: Generation of 1,2,5,6-heptatetraene (229) as a reaction intermediate.
Scheme 56: The preparation of a stable derivative of 1,2,5,6-heptatetraene.
Scheme 57: A bisallene with a carbonyl group as a spacer element.
Scheme 58: The first preparation of 1,2,6,7-octatetraene (242).
Scheme 59: Preparation of 1,2,6,7-octatetraenes by (C4 + C4)-coupling of enynes.
Scheme 60: Preparation of 1,2,6,7-octatetraenes by (C4 + C4)-coupling of homoallenyl bromides.
Scheme 61: Preparation of 1,2,6,7-octatetraenes by alkylation of propargylic substrates.
Scheme 62: Preparation of two highly functionalized 1,2,6,7-octatetraenes.
Scheme 63: Preparation of several higher α,ω-bisallenes.
Scheme 64: Preparation of different alkyl derivatives of α,ω-bisallenes.
Scheme 65: The preparation of functionalized 1,2,7,8-nonatetraene derivatives.
Scheme 66: Preparation of functionalized α,ω-bisallenes.
Scheme 67: The preparation of an α,ω-bisallene by direct homologation of an α,ω-bisalkyne.
Scheme 68: The gas-phase pyrolysis of 4,4-dimethyl-1,2,5,6-heptatetraene (237).
Scheme 69: Gas-phase pyrolysis of 1,2,6,7-octatetraene (242).
Scheme 70: The cyclopropanation of 1,2,6,7-octatetraene (242).
Scheme 71: Intramolecular cyclization of 1,2,6,7-octatetraene derivatives.
Scheme 72: The gas-phase pyrolysis of 1,2,7,8-nonatetraene (265) and 1,2,8,9-decatetraene (266).
Scheme 73: Rh-catalyzed cyclization of a functionalized 1,2,7,8-nonatetraene.
Scheme 74: A triple cyclization involving two different allenic substrates.
Scheme 75: Bicyclization of keto derivatives of 1,2,7,8-nonatetraene.
Scheme 76: The preparation of complex organic compounds from functionalized bisallenes.
Scheme 77: Cycloisomerization of an α,ω-bisallene containing a C9 tether.
Scheme 78: Organoborane polymers from α,ω-bisallenes.
Scheme 79: Preparation of trans- (337) and cis-1,2,4,6,7-octapentaene (341).
Scheme 80: The preparation of 4-methylene-1,2,5,6-heptatetraene (349).
Scheme 81: The preparation of acetylenic bisallenes.
Scheme 82: The preparation of derivatives of hydrocarbon 351.
Scheme 83: The construction of macrocyclic alleno-acetylenes.
Scheme 84: Preparation and reactions of 4,5-bismethylene-1,2,6,7-octatetraene (365).
Scheme 85: Preparation of 1,2-bis(propadienyl)benzene (370).
Scheme 86: The preparation of 1,4-bis(propadienyl)benzene (376).
Scheme 87: The preparation of aromatic and heteroaromatic bisallenes by metal-mediated coupling reactions.
Scheme 88: Double cyclization of an aromatic bisallene.
Scheme 89: Preparation of an allenic [15]paracyclophane by a ring-closing metathesis reaction of an aromatic α...
Scheme 90: Preparation of a macrocyclic ring system containing 1,4-bis(propadienyl)benzene units.
Scheme 91: Preparation of copolymers from 1,4-bis(propadienyl)benzene (376).
Scheme 92: A boration/copolymerization sequence of an aromatic bisallene and an aromatic bisacetylene.
Scheme 93: Formation of a layered aromatic bisallene.
Figure 4: The first members of the semicyclic bisallene series.
Scheme 94: Preparation of the first bis(vinylidene)cyclobutane derivative.
Scheme 95: Dimerization of strain-activated cumulenes to bis(vinylidene)cyclobutanes.
Scheme 96: Photodimerization of two fully substituted butatrienes in the solid state.
Scheme 97: Preparation of the two parent bis(vinylidene)cyclobutanes.
Scheme 98: The preparation of 1,3-bis(vinylidene)cyclopentane and its thermal isomerization.
Scheme 99: The preparation of the isomeric bis(vinylidene)cyclohexanes.
Scheme 100: Bi- and tricyclic conjugated bisallenes.
Scheme 101: A selection of polycyclic bisallenes.
Scheme 102: The first endocyclic bisallenes.
Figure 5: The stereochemistry of 1,2,6,7-cyclodecatetraene.
Scheme 103: The preparation of several endocyclic bisallenes.
Scheme 104: Synthesis of diastereomeric derivatives of 1,2,6,7-cyclodecatetraene.
Scheme 105: Preparation of a derivative of 1,2,8,9-cyclotetradecatetraene.
Scheme 106: The preparation of keto derivatives of cyclic bisallenes.
Scheme 107: The preparation of cyclic biscumulenic ring systems.
Scheme 108: Cyclic bisallenes in natural- and non-natural-product chemistry.
Scheme 109: The preparation of iron carbonyl complexes from cyclic bisallenes.
Figure 6: A selection of unknown exocyclic bisallenes that should have interesting chemical properties.
Scheme 110: The thermal isomerization of 1,2-diethynylcyclopropanes and -cyclobutanes.
Scheme 111: Intermediate generation of a cyclooctapentaene.
Scheme 112: Attempted preparation of a cyclodecahexaene.
Scheme 113: The thermal isomerization of 1,5,9-cyclododecatriyne (511) into [6]radialene (514).
Scheme 114: An isomerization involving a diketone derived from a conjugated bisallene.
Scheme 115: Typical reaction modes of heteroorganic bisallenes.
Scheme 116: Generation and thermal behavior of acyclic hetero-organic bisallenes.
Scheme 117: Generation of bis(propadienyl)thioether.
Scheme 118: The preparation of a bisallenic sulfone and its thermal isomerization.
Scheme 119: Bromination of the bisallenic sulfone 535.
Scheme 120: Metalation/hydrolysis of the bisallenic sulfone 535.
Scheme 121: Aromatic compounds from hetero bisallenes.
Scheme 122: Isomerization/cyclization of bispropargylic ethers.
Scheme 123: The preparation of novel aromatic systems by base-catalyzed isomerization of bispropargyl ethers.
Scheme 124: The isomerization of bisacetylenic thioethers to bicyclic thiophenes.
Scheme 125: Aromatization of macrocyclic bispropargylic sulfides.
Scheme 126: Preparation of ansa-compounds from macrocyclic bispropargyl thioethers.
Scheme 127: Alternate route for cyclization of a heterorganic bisallene.
Scheme 128: Multiple isomerization/cyclization of “double” bispropargylic thioethers.
Scheme 129: Preparation of a bisallenyl disulfide and its subsequent bicyclization.
Scheme 130: Thermal cyclization of a bisallenyl thiosulfonate.
Scheme 131: Some reactions of heteroorganic bisallenes with two sulfur atoms.
Scheme 132: Further methods for the preparation of heteroorganic bisallenes.
Scheme 133: Cyclization reactions of heteroorganic bisallenes.
Scheme 134: Thermal cycloadditions of bisallenic tertiary amines.
Scheme 135: Cyclization of a bisallenic tertiary amine in the presence of a transition-metal catalyst.
Scheme 136: A Pauson–Khand reaction of a bisallenic ether.
Scheme 137: Formation of a 2:1adduct from two allenic substrates.
Scheme 138: A ring-forming silastannylation of a bisallenic tertiary amine.
Scheme 139: A three-component cyclization involving a heterorganic bisallene.
Scheme 140: Atom-economic construction of a complex organic framework from a heterorganic α,ω-bisallene.
A novel asymmetric synthesis of cinacalcet hydrochloride
- Veera R. Arava,
- Laxminarasimhulu Gorentla and
- Pramod K. Dubey
Beilstein J. Org. Chem. 2012, 8, 1366–1373, doi:10.3762/bjoc.8.158
- 2695 chromatograph with a 2487 UV detector. Preparation of 2-methylpropane-2-sulfinic acid (1-naphthalen-1-ylethyl)amide (4): (R)-tert-Butanesulfinamide (2) (16.14 g, 0.133 mol) was added to a solution of titanium tetraethoxide (54.0 g, 0.236 mol) and 1-acetylnaphthalene (3, 20.0 g, 0.117 mol) in THF
Graphical Abstract
Figure 1: Cinalcet hydrochloride (CNC·HCl, 1).
Scheme 1: Asymmetric synthesis of 1.
Scheme 2: Synthesis of the intermediates 5 and 6 from 8.
Scheme 3: Asymmetric synthesis of naphthylethylsulfinamide 4.
Scheme 4: Conversion of 8 to 10.
Scheme 5: Synthesis of alcohol intermediate 12 from 10.
Scheme 6: Synthesis of bromo 5 and iodo 6 derivatives.
Scheme 7: Regioselective N-alkylation of naphthyl ethyl sulfinamide 4a.
Scheme 8: Acid hydrolysis of N-tert-butanesulfinyl group in 7.
Recyclable fluorous cinchona alkaloid ester as a chiral promoter for asymmetric fluorination of β-ketoesters
- Wen-Bin Yi,
- Xin Huang,
- Zijuan Zhang,
- Dian-Rong Zhu,
- Chun Cai and
- Wei Zhang
Beilstein J. Org. Chem. 2012, 8, 1233–1240, doi:10.3762/bjoc.8.138
- employed chiral titanium Lewis acid TiCl2(TADDOLate) for the asymmetric fluorination of β-ketoesters (up to 96% ee) [17][18][19][20]. Most Selectfluor-promoted asymmetric fluorinations require a stoichiometric amount of chiral promoters to suppress the competitively direct achiral fluorination. Different
Graphical Abstract
Figure 1: Biologically interesting α-fluorinated β-ketoesters.
Scheme 1: Preparation of quinine ester C-1.
Figure 2: Promoters for asymmetric fluorination.
Scheme 2: Preparation of 2a by using recycled quinine ester C-1.
Figure 3: The asymmetric fluorination of various β-ketoesters.
Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step
- Dieter Enders,
- Jeanne Fronert,
- Tom Bisschops and
- Florian Boeck
Beilstein J. Org. Chem. 2012, 8, 1112–1117, doi:10.3762/bjoc.8.123
- -position, both hydroxy groups were allylated, followed by a selective, titanium tetrachloride/tetra-n-butylammonium iodide mediated deprotection of the salicylic hydroxy group. The selectivity of this deprotection is caused by the chelating effect of the carbonyl oxygen towards titanium [12], directing the
Graphical Abstract
Figure 1: Furocoumarins.
Scheme 1: Synthesis of smyrindiol (1) by Grande et al.
Scheme 2: Synthesis of smyrindiol by Snider et al.
Scheme 3: Proline-catalyzed intramolecular aldol reaction of O-acetonyl-salicylaldehydes.
Scheme 4: First retrosynthetic analysis.
Scheme 5: Attempted proline catalyzed aldol reaction.
Scheme 6: Second retrosynthetic analysis.
Scheme 7: Asymmetric total synthesis of smyrindiol (1).
Reduction of benzylic alcohols and α-hydroxycarbonyl compounds by hydriodic acid in a biphasic reaction medium
- Michael Dobmeier,
- Josef M. Herrmann,
- Dieter Lenoir and
- Burkhard König
Beilstein J. Org. Chem. 2012, 8, 330–336, doi:10.3762/bjoc.8.36
- -group tolerance during this reduction step is essential since various other groups are usually present. A number of synthetic procedures have been developed, which allow selective reduction, but only a few one-step transformations are known, which use either titanium(III) [5][6][7][8] or different metal
Graphical Abstract
Scheme 1: Mechanism of the alcohol reduction and recycling of iodine.
Derivatives of phenyl tribromomethyl sulfone as novel compounds with potential pesticidal activity
- Krzysztof M. Borys,
- Maciej D. Korzyński and
- Zbigniew Ochal
Beilstein J. Org. Chem. 2012, 8, 259–265, doi:10.3762/bjoc.8.27
- made an attempt at synthesizing 2-arylbenzimidazole 11f and 11g according to our patented method [16]. The cyclization of diamine 9 with benzoic acids was run in anhydrous xylene with titanium tetrachloride as a catalyst (Scheme 7). 2-Mercaptobenzimidazole 11h was obtained by the reaction of diamine 9
Graphical Abstract
Scheme 1: Retrosynthetic analysis of the designed target molecules.
Scheme 2: Synthetic routes for 4-chlorophenyl tribromomethyl sulfone (1).
Scheme 3: Halogenation/nitration sequence for 4-halogenphenyl methyl sulfones 4 and 4'.
Scheme 4: SNAr transformations of sulfone 6.
Scheme 5: Preparation of phenylhydrazones 8a–8l.
Scheme 6: Products of the nitro group reduction of sulfone 7a.
Scheme 7: Synthesis of benzimidazole derivatives 11a–11g.
Scheme 8: Preparation and further transformation of 2-mercaptobenzimidazole 11h.
Fifty years of oxacalix[3]arenes: A review
- Kevin Cottet,
- Paula M. Marcos and
- Peter J. Cragg
Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22
- ]arene was Hampton’s variable temperature 1H NMR investigation of the interactions between titanium(IV) species and 3a [55]. In the absence of crystallographic evidence the NMR splitting patterns were compared to simulated spectra. At ambient temperature the NMR-derived symmetry was C3v, matching that of
- the macrocycle, but upon cooling an asymmetric Cs symmetry emerged. It was proposed that rapid interconversion between isomers occurred by a “turnstile” or Berry-pseudorotation mechanism. A subsequent paper from the group reported the crystal structure of the titanium(IV) isopropoxide (Ti(iPrO)4
- ) complex [56]. The structure was dimeric; each macrocycle was present as the trianion bound to the titanium by all three oxygens and pulled slightly into the cavity by iPrO−. The paper also reported the result of a reaction between the lithium salt of 3b and vanadyl chloride (VOCl3). Based on powder
Graphical Abstract
Figure 1: Calixarenes and expanded calixarenes: p-tert-Butylcalix[4]arene (1), p-tert-butyldihomooxacalix[4]a...
Figure 2: Conventional nomenclature for oxacalix[n]arenes.
Scheme 1: Synthesis of oxacalix[3]arenes: (i) Formaldehyde (37% aq), NaOH (aq), 1,4-dioxane; glacial acetic a...
Figure 3: p-tert-Butyloctahomotetraoxacalix[4]arene (4a) [16].
Figure 4: X-ray crystal structure of 3a showing phenolic hydrogen bonding (IUCr ID AS0508) [17].
Scheme 2: Stepwise synthesis of asymmetric oxacalix[3]arenes: (i) MOMCl, Adogen®464; (ii) 2,2-dimethoxypropan...
Figure 5: X-ray crystal structure of heptahomotetraoxacalix[3]arene 5 (CCDC ID 166088) [21].
Scheme 3: Oxacalix[3]arene synthesis by reductive coupling: (i) Me3SiOTf, Et3SiH, CH2Cl2; R1, R2 = I, Br, ben...
Scheme 4: Oxacalix[3]naphthalene: (i) HClO4 (aq), wet CHCl3 (R = tert-butyl, 6a, H, 6b) [20].
Figure 6: Conformers of 3a.
Scheme 5: Origin of the 25:75 cone:partial-cone statistical distribution of O-substituted oxacalix[3]arenes (p...
Scheme 6: Synthesis of alkyl ethers 7–10: (i) Alkyl halide, NaH, DMF [24].
Scheme 7: Synthesis of a pyridyl derivative 11a: (i) Picolyl chloride hydrochloride, NaH, DMF [26,27].
Figure 7: X-ray crystal structure of partial-cone 11a (CCDC ID 150580) [26].
Scheme 8: Lower-rim ethyl ester synthesis: (i) Ethyl bromoacetate, NaH, t-BuOK or alkali metal carbonate, THF...
Scheme 9: Forming chiral receptor 13: (i) Ethyl bromoacetate, NaH, THF; (ii) NaOH, H2O/1,4-dioxane; (iii) S-P...
Figure 8: X-ray crystal structure of 16 (IUCr ID PA1110) [32].
Scheme 10: Lower rim N,N-diethylamide 17a: (i) N,N-Diethylchloroacetamide, NaH, t-BuOK or alkali metal carbona...
Scheme 11: Capping the lower rim: (i) N,N-Diethylchloroacetamide, NaH, THF; (ii) NaOH, H2O/1,4-dioxane; (iii) ...
Figure 9: X-ray crystal structure of 18 (CCDC ID 142599) [33].
Scheme 12: Extending the lower rim: (i) Glycine methyl ester, HOBt, dicyclohexycarbodiimide (DCC), CH2Cl2; (ii...
Scheme 13: Synthesis of N-hydroxypyrazinone derivative 23: (i) 1-[3-(Dimethylamino)propyl]-3-ethylcarbodiimide...
Scheme 14: Synthesis of 24: (i) 1-Adamantyl bromomethyl ketone, NaH, THF [39].
Scheme 15: Synthesis of 25 and 26: (i) (Diphenylphosphino)methyl tosylate, NaH, toluene; (ii) phenylsilane, to...
Figure 10: X-ray crystal structure of 27 in the partial-cone conformer (CCDC ID SUP 90399) [41].
Scheme 16: Synthesis of strapped oxacalix[3]arene derivatives 28 and 29: (i) N,N’-Bis(chloroacetyl)-1,2-ethyle...
Figure 11: A chiral oxacalix[3]arene [45].
Figure 12: X-ray crystal structure of asymmetric oxacalix[3]arene 30 incorporating t-Bu, iPr and Et groups (CC...
Scheme 17: Reactions of an oxacalix[3]arene incorporating an upper-rim Br atom with (i) Pd(OAc)2, PPh3, HCO2H,...
Scheme 18: Synthesis of acid 39: (i) NaOH, EtOH/H2O, HCl (aq) [47].
Figure 13: Two forms of dimeric oxacalix[3]arene 40 [47].
Scheme 19: Capping the upper rim: (i) t-BuLi, THF, −78 °C; (ii) NaBH4, THF/EtOH; (iii) 1,3,5-tris(bromomethyl)...
Figure 14: Oxacalix[3]arene capsules 46 and 47 formed through coordination chemistry [52,53].
Figure 15: X-ray crystal structure of the 3b-vanadyl complex (CCDC ID 240185) [57].
Scheme 20: Effect of Ti(IV)/SiO2 on 3a: (i) Ti(OiPr)4, toluene; (ii) triphenylsilanol, toluene; (iii) partiall...
Figure 16: X-ray crystal structures of oxacalix[3]arene complexes with rhenium: 3b∙Re(CO)3 (CCDC ID 620981, le...
Figure 17: X-ray crystal structure of the La2·3a2 complex (CSD ID TIXXUT) [60].
Figure 18: X-ray crystal structures of [3a∙UO2]− with a cavity-bound cation (CCDC ID 135575, left) and without...
Figure 19: X-ray crystal structure of a supramolecule comprising two [3g·UO2]− complexes that encapsulate a di...
Figure 20: X-ray crystal structure of oxacalix[3]arene 49 capable of chiral selectivity (CSD ID HIGMUF) [65].
Figure 21: The structure of derivative 50 incorporating a Reichardt dye [66].
Figure 22: Phosphorylated oxacalix[3]arene complexes with transition metals: (Left to right) 26∙Au, 26∙Mo(CO)3...
Figure 23: X-ray crystal structure of [17a·HgCl2]2 (CCDC ID 168653) [69].
Figure 24: X-ray crystal structures of 3f with C60 (CCDC ID 182801, left) [76] and a 1,4-bis(9-fluorenyl) C60 deri...
Figure 25: X-Ray crystal structure of 3i and 6a encapsulating C60 (CCDC ID 102473 and 166077) [23,79].
Figure 26: A C60 complexing cationic oxacalix[3]arene 51 [81].
Figure 27: An oxacalix[3]arene-C60 self-associating system 53 [87].
Scheme 21: Synthesis of fluorescent pyrene derivative 55: (i) Propargyl bromide, acetone; (ii) CuI, 1-azidomet...
Scheme 22: Synthesis of responsive rhodamine derivative 57: (i) DCC, CH2Cl2 [91].
Scheme 23: Synthesis of nitrobenzyl derivative 58: (i) 1-Bromo-4-nitrobenzyl acetate, K2CO3, refluxing acetone...
Figure 28: X-ray crystal structure of [Na2∙17a](PF6)2 (CCDC ID 116656) [97].
Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters
- Lukas Hintermann,
- Mauro Perseghini and
- Antonio Togni
Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166
- Lukas Hintermann Mauro Perseghini Antonio Togni Laboratorium für Anorganische Chemie, ETH Zürich, Wolfgang-Pauli-Str. 10, 8093 Zürich, Switzerland Department Chemie, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany 10.3762/bjoc.7.166 Abstract Titanium-based
- Lewis acids catalyze the α-fluorination of β-ketoesters by electrophilic N–F-fluorinating reagents. Asymmetric catalysis with TADDOLato–titanium(IV) dichloride (TADDOL = α,α,α',α'-tetraaryl-(1,3-dioxolane-4,5-diyl)-dimethanol) Lewis acids produces enantiomerically enriched α-fluorinated β-ketoesters in
- TADDOL ligand structure on the catalytic activity and enantioselectivity were investigated. The absolute configuration of several fluorination products was assigned through correlation. Evidence for ionization of the catalyst complex by chloride dissociation, followed by generation of titanium β
Graphical Abstract
Figure 1: Fluorinated substances of biomedical relevance.
Scheme 1: Enantioselective electrophilic fluorination catalyzed by TADDOLates K1, K2. TADDOL = α,α,α',α'-tetr...
Scheme 2: Halogenation of β-ketocarbonyl compounds: Importance of enolization and the potential role of a met...
Figure 2: Model substrates for catalytic fluorinations, with the degree of enolization determined by 1H NMR m...
Figure 3: 1H NMR (250 MHz) spectra of fluorination reaction mixtures diluted with CDCl3 and filtered. a) Full...
Scheme 3: Qualitative ordering of catalytic activity of several Lewis acids in the fluorination 1→1-F.
Scheme 4: Catalysis of the “neutral” fluorination of β-ketoesters with F–TEDA by Lewis acidic titanium comple...
Figure 4: Structure of the chiral ansa-metallocene [(EBTHI)Ti(OTf)2].
Figure 5: Electrophilic fluorinating reagents of the N–F-type. F–TEDA [27]; NFTh = 1-fluoro-4-hydroxy-1,4-diazoni...
Scheme 5: Synthesis of trifluoromethyl-substituted TADDOL ligands.
Scheme 6: Correlation experiments for the assignment of absolute configuration to fluorination products 11-F, ...
Scheme 7: Mechanistic scheme proposed, based on visual and spectroscopic observations. L = solvent, counterio...
Figure 6: 1H NMR spectra of a species of the type A, generated in CD3CN solution from K1 by ionization in the...
Figure 7: Steric model explaining the face selectivity observed in the titanium–TADDOLate complex catalyzed f...
Figure 8: Excerpt from the X-ray structure of a catalyst/substrate complex [Ti(1-naphthyl-TADDOLato)(β-ketoen...
Cyclization of 5-hexynoic acid to 3-alkoxy-2-cyclohexenones
- Anne T. Hylden,
- Eric J. Uzelac,
- Zeljko Ostojic,
- Ting-Ting Wu,
- Keely L. Sacry,
- Krista L. Sacry,
- Lin Xi and
- T. Nicholas Jones
Beilstein J. Org. Chem. 2011, 7, 1323–1326, doi:10.3762/bjoc.7.155
- (26%). Titanium(IV) chloride was also screened, however no cyclization was observed. A dramatic increase in yield (71%) was obtained with the aid of indium(III) chloride. Additional metal chloride salts have been screened under our cyclization conditions (Table 1, entries 5–8). Although these salts
Graphical Abstract
Scheme 1: 3-Alkoxy-2-cyclohexenones from the cyclization of 5-hexynoyl chloride.
Scheme 2: Preparation of 3-chloro-2-cyclohexenone (4).
Scheme 3: Proposed pathway for the one-pot conversion of 5-hexynoic acid to 3-alkoxy-2-cyclohexenones.
Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate
- Michael North and
- Marta Omedes-Pujol
Beilstein J. Org. Chem. 2010, 6, 1043–1055, doi:10.3762/bjoc.6.119
- gives unprotected cyanohydrins which are prone to racemization. Pre-eminent amongst the synthetic catalysts are metal(salen) complexes, especially those based on titanium (1) and vanadium (2) [1] (Figure 1). Titanium complex 1 will catalyse the asymmetric addition of TMSCN to aromatic aldehydes with 80
- asymmetric addition of TMSCN [26][27][28] and KCN [13] to aldehydes and are more enantioselective, but less reactive than the titanium based catalyst 1. Complexes 1 and 2 have been commercialized [10][29][30], immobilized to facilitate their recycling [31][32][33][34][35][36][37][38][39][40][41][42][43] and
- used by other groups as part of synthetic studies [44][45][46]. Mechanistically, the mode of action of catalyst 1 is well understood [15][20][47][48][49], involving a bimetallic transition state in which one titanium atom acts as a Lewis acid, coordinating to the aldehyde, and the other forms a
Graphical Abstract
Scheme 1: Synthesis and transformation of nonracemic silyl-protected cyanohydrins.
Figure 1: Highly active metal(salen) complexes for asymmetric cyanohydrin synthesis.
Scheme 2: Synthesis of cyclic carbonates.
Scheme 3: Synthesis of cyanohydrin trimethylsilyl ethers and acetates.
Scheme 4: Equilibrium between bimetallic and monometallic Ti(salen) complexes.
Figure 2: Second-order kinetics plot for the addition of TMSCN to benzaldehyde at 0 °C catalysed by complex 2...
Figure 3: Plot of k2obs against [2], showing that the reactions are first order with respect to the concentratio...
Figure 4: Eyring plot to determine the activation parameters for catalyst 2 in propylene carbonate. The red a...
Figure 5: 51V NMR spectra of complex 2 recorded at 50 °C. a) Spectrum in CDCl3; b) spectrum in CDCl3 with 500...
Figure 6: Structures consistent with the 51V NMR spectra.
Figure 7: Bimetallic aluminium(salen) complex for asymmetric cyanohydrin synthesis.
Figure 8: Rate determining transition states for asymmetric cyanohydrin synthesis: a) when Lewis base catalys...
Figure 9: Hammett correlations with catalyst 2 at 0 °C. Data in red are obtained in dichloromethane [52], whilst ...
Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al2O3 under inspection
- Franziska Bernhardt,
- Ronald Trotzki,
- Tony Szuppa,
- Achim Stolle and
- Bernd Ondruschka
Beilstein J. Org. Chem. 2010, 6, No. 7, doi:10.3762/bjoc.6.7
- titanium silicalite, TiSiO4, showed moderate conversions in the range of basic γ-Al2O3 SRS3. Contrary to microwave-assisted reactions, MgO showed only little conversion when used as a base under ball milling conditions [34], whereas neutral oxides SiO2 and CeO2 did not show any conversion. Since the
Graphical Abstract
Scheme 1: Suzuki–Miyaura reaction of phenylboronic acid (1) with aryl bromides 2 yielding substituted biaryls ...
Figure 1: Results of the Suzuki–Miyaura reaction of phenylboronic acid (1) with p-bromoacetophenone (2a; cf. Scheme 1...
Figure 2: Results of the Suzuki–Miyaura reaction according to Scheme 1 assisted by pure aluminas [5 g SRS1–3: cf. Table 2; b...
Figure 3: Influence of Pd(OAc)2 concentration on the results of the Suzuki–Miyaura reaction of phenylboronic ...
Figure 4: Results of the Suzuki–Miyaura reaction according to Scheme 1 assisted by KF-loaded aluminas [5 g SRS1a–4a, ...
Figure 5: Dependence of the yield of Suzuki–Miyaura cross-coupling product (Scheme 1) from water content (Karl-Fische...
Three step synthesis of single diastereoisomers of the vicinal trifluoro motif
- Vincent A. Brunet,
- Alexandra M. Z. Slawin and
- David O'Hagan
Beilstein J. Org. Chem. 2009, 5, No. 61, doi:10.3762/bjoc.5.61
- reactions following Sharpless’ methodology [16]. The anti-epoxy alcohols were easily generated, however it proved more difficult to prepare the syn-epoxides cleanly. Treatment with titanium isopropoxide (Ti(OiPr)4) and D-diisopropyl tartrate (D-DIPT) favoured formation of the anti-α,β-epoxy alcohols. In the
Graphical Abstract
Scheme 1: Previous six step route to the vicinal all-syn-trifluoro motif.
Scheme 2: Novel three step successive fluorination strategy from α,β-epoxy alcohols to different diastereoiso...
Scheme 3: Synthesis approach to the requisite α,β-epoxy alcohols 6b and 7b.
Figure 1: X-ray structure (CCDC 750307) and stereochemistry of α,β-epoxy alcohol 7b.
Figure 2: X-ray structure (CCDC 750306) and stereochemistry of α,β-epoxy alcohol 7a.
Scheme 4: Three step sequential fluorination from α,β-epoxy alcohols to eg. the vicinyltrifluoro tosylate 11.
Scheme 5: Unexpected cyclisation of 9b to furan 14 with HF·pyridine. An X-ray structure of 14 (CCDC 750309) r...
Scheme 6: Epoxide ring opening of 9b with 3HF·Et3N required forcing conditions. The structure and stereochemi...
Scheme 7: Three step sequential fluorination from α,β-epoxy alcohol 7b to vicinal trifluoro tosylate 17b.
Scheme 8: Epoxide ring opening with 3HF∙Et3N and synthesis of the all-syn vicinal trifluoro tosylate 17a.
