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Search for "ketals" in Full Text gives 30 result(s) in Beilstein Journal of Organic Chemistry.
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.
Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives
- Carolin Regenbrecht and
- Siegfried R. Waldvogel
Beilstein J. Org. Chem. 2012, 8, 1721–1724, doi:10.3762/bjoc.8.196
- Carolin Regenbrecht Siegfried R. Waldvogel Institute for Organic Chemistry, Mainz University, Duesbergweg 10–14, 55128 Mainz, Germany 10.3762/bjoc.8.196 Abstract 2,3,6,7,10,11-Hexahydroxytriphenylene of good quality and purity can be obtained via anodic treatment of catechol ketals and subsequent
- . The shift of potentials is supported by cyclic voltammetry studies. Keywords: catechol; electrochemical oxidation; hexahydroxytriphenylene; ketals; propylene carbonate; Introduction The unique spectroscopic and geometric features of triphenylenes give rise to a variety of applications for this very
- Anodic oxidation of catechol ketals We report a simple protocol for the anodic oxidation of catechol ketals forming triphenylene ketals (Scheme 1). Best results were obtained in PC and TMABF4 (method A) or TBABF4 (method B) as electrolytes. Performing the reaction in PC is beneficial for several reasons
Graphical Abstract
Scheme 1: Experimental conditions for the anodic oxidation of catechol ketals.
Figure 1: Cyclic voltammograms of catechol ketal 1a in ACN and PC and triphenylene ketal 2a in ACN, for magni...
Scheme 2: Acid-catalyzed cleavage of ketal moieties.
Synthetic applications of gold-catalyzed ring expansions
- David Garayalde and
- Cristina Nevado
Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87
- . Acyloxylated alkynyl oxiranes 28 and 30 have also proved to be versatile building blocks for the synthesis of divinyl ketones 29 [29], 2,5-disubstituted furans 31 [30] and difurylmethane derivatives 32 [31], respectively (Scheme 10). Epoxy alkynes can also be transformed with high stereoselectivity into ketals
- the alkyne and intramolecular nucleophilic attack of the alcohol function to give 34. Reactivation of the olefin and subsequent incorporation of a second molecule of nucleophile (intramolecularly in the case of water, intermolecularly in the case of alcohols) affords ketals 35 and 36, respectively
- oxiranes. Transformations of alkynyl oxiranes into ketals. Gold-catalyzed cycloisomerization of cyclopropyl alkynes. Gold-catalyzed synthesis of substituted furans. Proposed mechanism for the isomerization of alkynyl cyclopropyl ketones. Cycloisomerization of cyclobutylazides. Cycloisomerization of alkynyl
Graphical Abstract
Scheme 1: Transition metal promoted rearrangements of bicyclo[1.1.0]butanes.
Scheme 2: Gold-catalyzed rearrangements of strained rings.
Scheme 3: Gold-catalyzed ring expansions of cyclopropanols and cyclobutanols.
Scheme 4: Mechanism of the cycloisomerization of alkynyl cyclopropanols and cyclobutanols.
Scheme 5: Proposed mechanism for the Au-catalyzed isomerization of alkynyl cyclobutanols.
Scheme 6: Gold-catalyzed cycloisomerization of 1-allenylcyclopropanols.
Scheme 7: Gold-catalyzed cycloisomerization of cyclopropylmethanols.
Scheme 8: Gold-catalyzed cycloisomerization of aryl alkyl epoxides.
Scheme 9: Gold-catalyzed synthesis of furans.
Scheme 10: Transformations of alkynyl oxiranes.
Scheme 11: Transformations of alkynyl oxiranes into ketals.
Scheme 12: Gold-catalyzed cycloisomerization of cyclopropyl alkynes.
Scheme 13: Gold-catalyzed synthesis of substituted furans.
Scheme 14: Proposed mechanism for the isomerization of alkynyl cyclopropyl ketones.
Scheme 15: Cycloisomerization of cyclobutylazides.
Scheme 16: Cycloisomerization of alkynyl aziridines.
Scheme 17: Gold-catalyzed synthesis of disubstituted cyclohexadienes.
Scheme 18: Gold-catalyzed synthesis of indenes.
Scheme 19: Gold-catalyzed [n + m] annulation processes.
Scheme 20: Gold-catalyzed generation of 1,4-dipoles.
Scheme 21: Gold-catalyzed synthesis of repraesentin F.
Scheme 22: Gold-catalyzed ring expansion of cyclopropyl 1,6-enynes.
Scheme 23: Gold-catalyzed synthesis of ventricos-7(13)-ene.
Scheme 24: 1,2- vs 1,3-Carboxylate migration.
Scheme 25: Gold-catalyzed cycloisomerization of vinyl alkynyl cyclopropanes.
Scheme 26: Proposed mechanism for the cycloisomerization of vinyl alkynyl cyclopropanes.
Scheme 27: Gold-catalyzed 1,2-acyloxy rearrangement/cyclopropanation/cycloisomerization cascades.
Scheme 28: Formal total synthesis of frondosin A.
Scheme 29: Gold-catalyzed rearrangement/cycloisomerization of cyclopropyl propargyl acetates.
An efficient partial synthesis of 4′-O-methylquercetin via regioselective protection and alkylation of quercetin
- Nian-Guang Li,
- Zhi-Hao Shi,
- Yu-Ping Tang,
- Jian-Ping Yang and
- Jin-Ao Duan
Beilstein J. Org. Chem. 2009, 5, No. 60, doi:10.3762/bjoc.5.60
- available for the cleavage of such diphenylmethylene ketals: hydrogenolysis or hydrolysis. Under hydrogenation conditions the ketal could be cleaved selectively. The best results were obtained with 10% palladium on carbon as the catalyst in THF/EtOH. TLC showed that the reaction was complete after 8 h. This
Graphical Abstract
Figure 1: Structures of quercetin and methylated metabolites.
Scheme 1: Synthesis of 4′-O-methylquercetin (2, tamarixetin). a) Ph2CCl2, Ph2O, 175 °C, 30 min, 86%; b) MOMCl...
Figure 2: ROESY correlations of compound 2.
Part 1. Reduction of S-alkyl- thionocarbonates and related compounds in the presence of trialkylboranes/air
- Jean Boivin and
- Van Tai Nguyen
Beilstein J. Org. Chem. 2007, 3, No. 45, doi:10.1186/1860-5397-3-45
- ]. Secondary xanthates 7a and 8a, bearing an acetyl group, were also reduced, but in slightly lower yields (entries 6, 7). The reduction with Et3B/air is also adapted to S-alkylxanthates which are a part of fragile compounds such as ketals or carbonyl derivatives that contain a leaving group in the β-position
Graphical Abstract
Figure 1: Reaction of α-acylxanthate 1a with 1-decene and Et3B/air.
Figure 2: Xanthates and thionoimidazolides 2–16 and their reduced derivatives.
Scheme 1: Reduction of xanthate 17a at different temperatures with Et3B (5 equiv.)/air.
Scheme 2: Reduction of S-alkylxanthates and O-alkylxanthates.
Scheme 3: Reduction of O-alkyl-S-methyl xanthate 19, thionoimidazolide 21 and iodide 22 by Et3B/air at 20°C.
Scheme 4: Products formed through a putative 1,5-hydrogen atom transfer.
