Showing papers in "Synthesis in 1994"
TL;DR: In this paper, a review of the oxidations of a wide range of molecules with tetrapropylammonium perruthenate including examples of both double oxidations and selective oxidations is presented.
Abstract: This article reviews the oxidations of a wide range of molecules with tetrapropylammonium perruthenate including examples of both double oxidations and selective oxidations. Mechanistic studies are discussed and general experimental procedures are reported. In addition several interesting developments in the chemistry of this reagent are outlined, that is, heteroatom oxidation, cleavage reactions and also its use in sequential reaction processes. In order to present a complete picture examples of failed reactions have been included
1,029 citations
390 citations
TL;DR: The reactions reviewed in this article are those that show an unusual outcome when performed in water or in an aqueous medium, except when they are clearly due to the polarity as for example in nucleophilic substitution reactions.
Abstract: The reactions reviewed herein are those showing an unusual outcome when performed in water or in an aqueous medium. Notably, transformations are included for which the hydrophobic effect might be invoked as the activation factor, as well as cases where water leads to valuable chan- ges compared to traditional solvents, except when they are clearly due to the polarity as for example in nucleophilic substitution reactions and except when the effect comes from the addition of a few equivalents of water
351 citations
TL;DR: In this paper, a review summarizes the progress which has been made in the development of efficient chiral auxiliary groups and catalysts for steric steering of aza, oxa and thia Diels-Alder cycloadditions and thereby describes the current state of the art.
Abstract: Asymmetric hetero Diels-Alder reactions provide a multitude of oppor- tunities for the highly efficient regio- and stereoselective construc- tion of various heterocycles in enantiomerically pure form. Despite the great potential of this synthetic methodology, its development was for a long time restrited to only a few efforts. However, during the last decade this field has been the subject of intense and successful acti- vities. This review summarizes the progress which has been made in the development of efficient chiral auxiliary groups and catalysts for the steric steering of aza, oxa and thia Diels-Alder cycloadditions and thereby describes the current state of the art
232 citations
221 citations
TL;DR: In this paper, a number of new methodologies have been successfully applied to the preparation of optically active fragments toward the synthesis to more complex molecules and natural products. But none of these methods are suitable for the synthesis of complex molecules.
Abstract: Recent developments in the regio-, chemo- and stereoselective oxirane cleavage by new halogenating reagents allow obtention of various vicinal halohydrins. Also, epoxy alcohols and other functionalized oxiranes can be conveniently converted into the corresponding halohydrins. Some of the new methodologies have been successfully applied to the preparation of optically active fragments toward the synthesis to more complex molecules and natural products
178 citations
TL;DR: An improved and efficient synthesis of tetrathiafulvalene-2,3,6,7-te-trathiolate (TTFTT) was reported in this paper.
Abstract: An improved and efficient synthesis of tetrathiafulvalene-2,3,6,7-te- trathiolate (TTFTT) (5) is reported. TTF-tetrathiolate (5) was generated from 2,3,6,7-tetrakis(2'-cyanoethylthio)tetrathiafulvalene (11) under basic conditions at room temperature and was subsequently reacted with a range of electrophiles giving improved synthesis of known systems as well as new TTF-derivatives in excellent yields
174 citations
162 citations
TL;DR: Methods for the preparation of C-aryl glycosides, and their application to the total synthesis of naturally occurring C -aryl glycolysisides, are reviewed in this article.
Abstract: Methods for the preparation of C-aryl glycosides, and their application to the total synthesis of naturally occurring C-aryl glycosides, are reviewed
139 citations
131 citations
TL;DR: An improved procedure for the preparation of 1,1-dimethylethyl 2,2-dimethyl-4-(S)-formyloxazolidine-3-carboxylate (Garner aldehyde) is described in this article.
Abstract: An improved procedure for the preparation of 1,1-dimethylethyl 2,2-dimethyl-4-(S)-formyloxazolidine-3-carboxylate (Garner aldehyde) is described which avoids the need for methyl iodide and benzene. Elaboration of this aldehyde into the novel chiral building blocks mentioned in the title is also described
TL;DR: The most important classes of precursor molecules are 2-diazo-1, 3-diketones, 1,3dioxin-4-ones, 2,3-dihydrofuran-2, 3diones, and beta-ketoacid derivatives as mentioned in this paper.
Abstract: This review describes the methods of generation of alpha-oxoketenes and their use in synthesis. While the ketenes are often generated in situ without direct proof for their existence, methods used for their direct observation are also emphasized. The most important classes of precursor molecules are 2-diazo-1,3-diketones, 1,3-dioxin-4-ones, 2,3-dihydrofuran-2,3-diones, and beta-ketoacid derivatives. Synthetically useful reactions are nucleophilic additions to give carboxylic acid derivatives which can be subjected to further functional group manipulation, [2 + 2] cycloadditions to give four-membered rings, and [2 + 4] cycloaddition chemistry with a wide variety of double-and triple-bonded dienophiles, resulting in numerous six-membered heterocyclic ring systems.
TL;DR: In this article, the synthesis of the title compounds 2-4, which are important precursors of highly functionalised tetrathiafulvalene derivatives and multistage redox assemblies, are described.
Abstract: Reproducible, high-yielding synthesis of the title compounds 2-4, which are important precursors of highly functionalised tetrathiafulvalene derivatives and multistage redox assemblies, are described. This is demonstrated by the subsequent reactions of 3 and 4 to prepare compounds 9-16; the single crystal X-ray structure of TTF derivative 15 is described
TL;DR: 1-H-Pyrazole-1-[N,N-bis(tert-butoxycarbonyl)]carboxamidine (1) reacts under mild conditions with a number of amines and amino acids to give the respective protected guanidines in moderate to high isolated yields as mentioned in this paper.
Abstract: 1-H-Pyrazole-1-[N,N'-bis(tert-butoxycarbonyl)]carboxamidine (1) reacts under mild conditions with a number of amines and amino acids to give the respective protected guanidines in moderate to high isolated yields
TL;DR: In this article, a review describes the methods of preparation and use of isomunchnones and thioisomunknones to synthesize furans, 2-pyridones, functionalized lactams and other heterocyclic ring systems.
Abstract: This review describes the methods of preparation and use of isomunchnones and thioisomunchnones to synthesize furans, 2-pyridones, functionalized lactams and other heterocyclic ring systems. Some promising intramolecular dipolar cycloadditions of these mesoionic compounds, and their potential for natural product syntheses, are presented
TL;DR: In this paper, a solvent free reaction in the presence of carefully adjusted amounts of piperidine leads to Knoevenagel products in good yields, within 3 to 15 minutes under microwave irradiation by a solvent-free reaction.
Abstract: Condensation of carbonyl derivatives 2 with active methylene compounds 1 is efficiently achieved, within 3 to 15 minutes under microwave irradiation by a solvent free reaction in the presence of carefully adjusted amounts of piperidine leading to Knoevenagel products 3 in good to excellent yields.
TL;DR: The use of benzotriazole as a synthetic auxiliary for the preparation of numerous organic derivatives is reviewed in this article, where it is proved to be efficient amino-alkylation, amidoalkylization, alkoxyalkylations, acyloxyalkyation, and thioalkylating agents for many classes of compounds.
Abstract: Recent advances in the use of benzotriazole as a synthetic auxiliary for the preparation of numerous organic derivatives are reviewed. Benzotriazolyl derivatives are converted into other benzotriazolyl intermediates for further transformations. The displacement of the benzotriazole moiety by nucleophiles affords many useful organic compounds. Thus, (α-heteroalkyl)benzotriazoles are proved to be efficient aminoalkylation, amidoalkylation, alkoxyalkylation, acyloxyalkylation, and thioalkylation agents for many classes of compounds
TL;DR: In this paper, the improved synthesis of hexaazatriphenylene (HAT) derivatives in good yields, high purity, and without the use of expensive solvents is reported.
Abstract: The synthesis of hexaazatriphenylene (HAT) derivatives, including the title compound, have been reported previously. However, due to problems with purity, low yields and expensive solvents, their potential utility has yet to be fully realized. We now report the improved synthesis of HAT derivatives in good yields, high purity, and without the use of expensive solvents
TL;DR: In this paper, the base-catalyzed condensation of benzyl isocyanoacetate with α-acetoxynitro compounds, or nitroalkenes, in refluxing tetrahydrofuran was described.
Abstract: Benzyl esters of 5-unsubstituted pyrrole-2-carboxylic acids were prepared in excellent yields by the base-catalyzed condensation of benzyl isocyanoacetate with α-acetoxynitro compounds, or nitroalkenes, in refluxing tetrahydrofuran. These pyrrolic products are important intermediates in the synthesis of porphyrins and related compounds
TL;DR: A reagent prepared from a 1: 2 molar ratio of (diacetoxy)iodobenzene [PhI(OAc) 2 ] and trifluoromethanesulfonic acid (TfOH) reacts with aromatic compounds to give diaryliodonium triflates in fairly good yields as discussed by the authors.
Abstract: A reagent prepared from a 1: 2 molar ratio of (diacetoxy)iodobenzene [PhI(OAc) 2 ] and trifluoromethanesulfonic acid (TfOH) reacts with aromatic compounds to give diaryliodonium triflates in fairly good yields. The high reactivity and high para selectivity of the reagent [PhI(OAc) 2 -2TfOH] are described