Showing papers in "Synthesis in 1990"
TL;DR: In this paper, the most important developments in the use of activated DMSO for the oxidation of alcohols since 1981 through 1989, but includes sufficient coverage of the earlier literature so as to be self-contained.
Abstract: The current review is intended to emphasize the most important developments in the use of activated DMSO for the oxidation of alcohols since 1981 through 1989, but includes sufficient coverage of the earlier literature so as to be self-contained. Only enough of the vast number of recent references are cited to highlight advances in the methodology and to provide recent examples of the application of these reactions.
353 citations
TL;DR: A review of the use of baker's yeast as a reagent in organic synthesis can be found in this article, with an emphasis on the developments of the last 15 years, and the transformations of various classes of compounds are examined, for example, reduction or formation of double bonds, acyloin condensation.
Abstract: The review examines the use of baker's yeast as a reagent in organic synthesis, with an emphasis on the developments of the last 15 years. The transformations of various classes of compounds are examined, for example, reduction or formation of double bonds, acyloin condensation. The equivalent microbial transformations are compared in relevant cases
340 citations
TL;DR: In this paper, the authors reviewed the new possibilities in organic synthesis offered by the electroreduction of organic halides in the presence of various electrophiles using sacrificial metallic anodes.
Abstract: This article reviews the new possibilities in organic synthesis offered by the electroreduction of organic halides in the presence of various electrophiles using sacrificial metallic anodes
188 citations
TL;DR: In this article, a review examines some typical examples that illustrate the significant developments reported recently, in which external chiral ligands have been used as asymmetric controllers in stoichiometric and catalytic amounts.
Abstract: This review examines some typical examples that illustrate the significant developments reported recently, in which external chiral ligands have been used as asymmetric controllers in stoichiometric and catalytic amounts
169 citations
TL;DR: 6-O-Monoesters of alkyl glucopyranosides have been prepared on a large scale in a more than 90% yield by direct enzyme-catalysed esterification of glucopyrsides with long chain fatty acids in a solvent-free process.
Abstract: 6-O-Monoesters of alkyl glucopyranosides have been prepared on a large scale in a more than 90% yield by direct enzyme-catalysed esterification of glucopyranosides with long chain fatty acids in a solvent-free process
159 citations
TL;DR: In this article, Georg Thieme et al. describe the generation of Benzyne and its reaction to Indolyliodonium salts and their reactions to perfluoroalkylation.
Abstract: PDF (1085 kb) Your Current IP Address: 184.170.131.156 © 2018 Georg Thieme Verlag KG | Imprint | Privacy policy statement | Smartphone Version Salts 11.3. Perfluoroalkylations 11.4. Reactions of Indolyliodonium salts 11.5. C-Arylation of Various Substrates Using Diaryliodonium Salts 11.6. Generation of Benzyne and Its Reactions 12. Conclusion
153 citations
TL;DR: Ketene dithioacetals are reviewed in this article as versatile building blocks in a multitude of synthetically useful transformations, including cyclizations, C-C bond formation and in the synthesis of heterocyclic systems.
Abstract: Ketene dithioacetals are reviewed as versatile building blocks in a multitude of synthetically useful transformations. After discussing the methods for preparation of ketene dithioacetals, their application in cyclizations, C-C bond formation and in the synthesis of heterocyclic systems will be described. Their use as carboxyl equivalents, which display an umpolung-type reactivity pattern will be emphasized
133 citations
TL;DR: In this paper, a title reaction gives pyridine derivatives corresponding to the title compounds in excellent yields, which are then used to synthesize pyridines. But they are not suitable for use in chemical synthesis.
Abstract: Title reaction gives pyridine derivatives corresponding to the title compounds in excellent yields
126 citations
TL;DR: In the presence of the diisopropyl azodicarboxylate/triphenylphosphine couple, alcohols react with zinc azide/bis-pyridine complex to give various azides via a Mitsunobu-type substitution as discussed by the authors.
Abstract: In the presence of the diisopropyl azodicarboxylate/triphenylphosphine couple, alcohols react with zinc azide/bis-pyridine complex to give various azides via a Mitsunobu-type substitution.
118 citations
TL;DR: In this paper, the authors show that (R)-Cyanohyrins, prepared in good to excellent yields with high optical purity by enzyme-catalyzed addition of hydrogen cyanide to aldehydes in organic solvents, are hydrolyzed with concentrated hydrochloric acid at ambient temperature, usually in very high yield, without any trace of racemization to give α-hydroxy carboxylic acids.
Abstract: In der vorliegenden Arbeit wird die Hydrolyse und die Hydrierung von (R)-Cyanhydrinen zu α-Hydroxycarbonsauren (R)-3 und 1- Amino-2-alkoholen (R)-6 beschrieben.
(R)-Cyanohyrins, prepared in good to excellent yields with high optical purity by enzyme-catalyzed addition of hydrogen cyanide to aldehydes in organic solvents, are hydrolyzed with concentrated hydrochloric acid at ambient temperature, usually in very high yield, without any trace of racemization to give (R)-α-hydroxy carboxylic acids. Likewise, no racemization is observed by direct reduction of the (R)-cyanohydrins with lithium aluminum hydride to give (2R)-1-amino-2-alkanols.
104 citations
TL;DR: N-Protected amino acids and peptides are converted to alcohols by chemoselective reduction of their corresponding mixed anhydrides with sodium borohydride in tetrahydrofuran with dropwise addition of methanol as mentioned in this paper.
Abstract: N-Protected amino acids and peptides are converted to alcohols by chemoselective reduction of their corresponding mixed anhydrides with sodium borohydride in tetrahydrofuran with dropwise addition of methanol
TL;DR: The transformations of carbon-sulfur bonds into carbon-hydrogen and carbon-carbon bonds under homogeneous conditions are discussed in this paper, where the reduction methods using metal carbonyls, low-valent transition metal complexes, metal hydrides, Grignard reagents and transition metal compounds as reducing agents are presented.
Abstract: The transformations of carbon-sulfur bonds into carbon-hydrogen and carbon-carbon bonds under homogeneous conditions are discussed. The reduction methods using metal carbonyls, low-valent transition metal complexes, metal hydrides, Grignard reagents and transition metal compounds as reducing agents are presented. The reactions leadsing to the carbon-carbon bond formation by coupling with main group organometallic nucleophioles, desulfurdimerization, carbonylation and related methods are reviewed. Some other synthetically useful reactions involving the cleavage of carbon-sulfur bonds are also briefly discussed
TL;DR: In this paper, recent progress in the methodology for stereoselective synthesis of 1,3-polyol functions is reviewed and strategies for the synthesis of the extended 1 3 polyol chain are also described.
Abstract: Recent progress in the methodology for stereoselective synthesis of the 1,3-polyol functions is reviewed. Strategies for the synthesis of the extended 1,3-polyol chain are also described
TL;DR: In this article, a survey of industrial applications of palladium catalysts as homogeneous and heterogeneous catalysts is surveyed, and some promising palladium-catalyzed reactions which may be used in commercial processes in future are included.
Abstract: Rapidly expanding industrial applications of palladium catalysts as homogeneous and heterogeneous catalysts are surveyed. They are classified into two types. The first type includes the oxidative reactions of olefins and aromatic compounds, and oxidative carbonylation. These reactions are catalyzed by Pd(II) salts and appropriate reoxidants. Reactions catalyzed by Pd(0) complexes are the second type, which includes reactions of organic halides and reactions via π-allylpalladium complexes. Also some promising palladium-catalyzed reactions, which may be used in commercial processes in future, are included. 1. Introduction 2. Oxidative Reactions Catalyzed by Pd(II) Salts 2.1. Oxidative Reactions of Olefins 2.2. Oxidative Reactions of Aromatic Compounds 2.3. Oxidative Carbonylation and Other Reactions 2.4. Summary 3. Reactions Catalyzed by Pd(0) Complexes 3.1. Reactions of Alkenyl and Aryl Halides 3.2. Catalytic Reactions of Allylic Compounds and Conjugated Dienes via π-Allylpalladium Complexes 3.3. Carbonylation of Olefins 4. Concluding Remarks
TL;DR: Palladium-catalyzed cyclization of β-(2-halophenyl)amino substituted α,β-unsaturated ketones and esters, prepared from 2-haloanilines by three different methods, gave 2,3-disubstituted indoles as discussed by the authors.
Abstract: Palladium-catalyzed cyclization of β-(2-halophenyl)amino substituted α,β-unsaturated ketones and esters, prepared from 2-haloanilines by three different methods, gave 2,3-disubstituted indoles.
TL;DR: In contrast to other methods of reduction, catalytic transfer hydrogenation allows debenzylation of a phenolic hydroxyl in a carbinolamine-containing pyrolo[2,1-c][1,4]benzodiazepine, while leaving the biologically important carbinoline moiety intact as mentioned in this paper.
Abstract: In contrast to other methods of reduction, catalytic transfer hydrogenation allows debenzylation of a phenolic hydroxyl in a carbinolamine-containing pyrolo[2,1-c][1,4]benzodiazepine, while leaving the biologically-important carbinolamine moiety intact. This has been demonstrated by synthesis of the naturally occurring antitumour antibiotic DC-81 (10). An efficient synthesis of 4-benzyloxy-5-methoxy-2-nitrobenzoic acid (5), an important intermediate in the production of certain pyrrolobenzodiazepine antitumour agents, is also reported
TL;DR: In this article, a large scale synthesis of complicated dipyrrinones, such as xanthobilirubic acid methyl ester (9), can be obtained from simple, inexpensive starting materials like ethyl acetoacetate, 2,4-pentanedione, and ethyl acrylate in 8 steps with an average yield of 80% at each step and an overall 17% yield.
Abstract: Structurally interesting and complicated dipyrrinones, such as xanthobilirubic acid methyl ester (9), can be synthesized on a large scale from simple, inexpensive starting materials like ethyl acetoacetate, 2,4-pentanedione (1) and ethyl acrylate in 8 steps with an average yield of 80% at each step and an overall 17% yield
TL;DR: In this article, the major (αR) isomers with Grignard reagents yield the products of displacement of chloride by alkyl (S)-3, (1R,2R)-25, ( 1R, 2R)-26, (R,R)-27, respectively in 98% diastereoisomeric excess.
Abstract: (S,S)-Diisopropylethanediol (S) 6, (S,S)-DIPED] boronic esters 1? (S)-3, (S)-9, 11 with (dichloromethyl)lithium yield the chain extended (αR)-(α-chloroalkyl)boronic esters (S)-2, (1R,2R)-24, (1R,2S)-24, (R)-27, respectively in 98% diastereoisomeric excess. The major (αR) isomers with Grignard reagents yield the products of displacement of chloride by alkyl (S)-3, (1R,2R)-25, (1R,2S)-25, (S)-9. The enantiomers have been made from (R,R)-DIPED. Contrakinetic (S,S)-DIPED (αS)-(α-chloroalkyl)boronate (S)-7 has been prepared indirectly and found to undergo a different major reaction with methylmagnesium bromide which leads to B-methyl-1,4,2-dioxaborinane 10. Thus, in the two-step formation of a new chiral center, the minor isomer is twice discriminated against. The utility of this new chemistry has been demonstrated with the asymmetric synthesis of each of the four stereoisomers of 4-methyl-3-heptanol (26) in very high purity. Diastereoselectivities measured at 350:1 to 1000:1 per chiral center have been achieved
TL;DR: In this article, the structure of these products as ketene N,S-acetals is confirmed by spectroscopic data, and they are shown to react with esters of α,β-yunsaturated acids to give thiazolo[3,2-a]pyrid-5-one derivatives.
Abstract: Ketene S,S-acetals 2 react with 2-almino-1-ethanethiol to afford the substituted 2-methylenethiazolidines 3. The structure of these products as ketene N,S-acetals is confirmed by spectroscopic data. Compounds 3a-f react with esters of α,β-yunsaturated acids to give thiazolo[3,2-a]pyrid-5-one derivatives 4, 6, and 7 through an electrophilic addition and cyclocondensation sequences
TL;DR: In this article, N α -tert-butoxycarbonyl α,ω-alkanediamine hydrochlorides 3a-e were prepared from the amino alcohols in yields of 66-87%.
Abstract: N α -tert-butoxycarbonyl α,ω-alkanediamine hydrochlorides 3a-e are prepared from the amino alcohols in yields of 66-87%. Reaction of the free amine with di-tert-butyl dicarbonate gives the N-tert-butoxycarbonylamino alcohol 1a-e. One-pot conversion to the azide 2a-e via the mesylate under phase-transfer conditions followed by hydrogenolysis in the presence of chloroform yields the tittle compounds
TL;DR: Hetero-Diels-alder reaction of β,β-bis(trifluoroacetyl)vinyl ethers, which are prepared by acylation of vinyl ethers with trifluoracetic anhydride, with electron-rich alkenes such as vinyl ether, ethyl vinyl sulfide and 1,1-diphenoxyethylene proceed quite easily under mild conditions to afford 2,4-dialkoxy-, 2,ethoxy-4-phenoxy-, 3,4dihydro-2H
Abstract: Hetero-Diels-alder reaction of β,β-bis(trifluoroacetyl)vinyl ethers, which are prepared by acylation of vinyl ethers with trifluoroacetic anhydride, with electron-rich alkenes such as vinyl ethers, ethyl vinyl sulfide and 1,1-diphenoxyethylene proceed quite easily under mild conditions to afford 2,4-dialkoxy-, 2-ethoxy-4-phenoxy-, 2-ethylthio-4-alkoxy-, 2-2diphenoxy-4-ethoxy- and 2,4-diaryloxy-5-trifluoroacetyl-6-trifluoromethyl-3,4-dihydro-2H-pyrans in excellent yields
TL;DR: Trifluoromethylsulfonyl substituted aromatic compounds 3a-d are prepared from the corresponding sulfonyl fluorides 1a-D by reacting with (trifluorsyl)trimethylsilane (or-stannane) in the presence of a base under mild conditions in high yields as mentioned in this paper.
Abstract: Trifluoromethylsulfonyl substituted aromatic compounds 3a-d are prepared from the corresponding sulfonyl fluorides 1a-d by reacting with (trifluoromethyl)trimethylsilane (or-stannane) in the presence of a base under mild conditions in high yields
TL;DR: Both enantiomers of erythro-3-hydroxyleucine are available by asymmetric epoxidation of (E)-4-methyl-2-penten-1-ol (1) followed by ruthenium tetroxide catalyzed oxidation to the corresponding glycidic acid 3, epoxide opening by benzylamine, and hydrogenolysis using palladium hydroxide on carbon as mentioned in this paper.
Abstract: Both enantiomers of erythro-3-hydroxyleucine are available by asymmetric epoxidation of (E)-4-methyl-2-penten-1-ol (1) followed by ruthenium tetroxide catalyzed oxidation to the corresponding glycidic acid 3, epoxide opening by benzylamine, and hydrogenolysis using palladium hydroxide on carbon
TL;DR: In this paper, an efficient preparation procedure of optically pure Wieland-Miescher ketone, (8aR)-(−)-3,4,8,8a-tetrahydro-8amethyl-1,6(2H,7H)-naphthalenedione (1), is described, and its absolute stereochemistry is confirmed by the CD exciton chirality method to its derivatives.
Abstract: An efficient preparation procedure of optically pure Wieland-Miescher ketone, (8aR)-(−)-3,4,8,8a-tetrahydro-8a-methyl-1,6(2H,7H)-naphthalenedione (1), is described, and its absolute stereochemistry is confirmed by the application of the CD exciton chirality method to its derivatives
TL;DR: A simple and efficeint synthesis of protected D-ribonolactone, a key chiral precursor used in the syntheses of neplanocin A and cyclopentenylcytosine from readily available Dribose is reported in this paper.
Abstract: A simple and efficeint synthesis of protected D-ribonolactone, a key chiral precursor used in the syntheses of neplanocin A and cyclopentenylcytosine from readily available D-ribose is reported
TL;DR: In this article, the synthesis of stable acyloxymethyl carbonochloridates 7 has been accomplished in four steps from chloromethyl CO 3 to carbonothioate 6cc by chlorination with sulfuryl chloride.
Abstract: The synthesis of a number of stable acyloxymethyl carbonochloridates 7 has been accomplished in four steps from chloromethyl carbonochloridate 3. Each step has been optimized with propanoyl-oxymethyl carbonochloridate 7c as a model compound (64% overall yield). Diethyl ether-boron trifluoride catalyzes the conversion of carbonothioate 6cc to the carbonochloridate 7c by chlorination with sulfuryl chloride. Acylation of a few compounds containing hydroxy or amino groups by 7c is described
TL;DR: The reaction between internal alkynes and 1-iodo-8-dimethylaminonaphthalene in the presence of catalytic amounts of a cyclopalladated compound provides a new route to N-methyl-benzo[d, e]quinolines as discussed by the authors.
Abstract: The reaction between internal alkynes and 1-iodo-8-dimethylaminonaphthalene in the presence of catalytic amounts of a cyclopalladated compound provides a new route to N-methyl-benzo[d,e]quinolines
TL;DR: In this article, the title ring system was derived in enantiomerically pure form from trans-4-hydroxy-L-proline and the target compounds were precursors of antibacterial quinolone carboxylic acids.
Abstract: Derivatives of the title ring system are prepared in enantiomerically pure form from trans-4-hydroxy-L-proline . The target compounds are precursors of antibacterial quinolone carboxylic acids.