Palladium-catalyzed asymmetric allylic alkylation of meso- and dl-1,2-divinylethylene carbonate

The palladium-catalyzed asymmetric allylic alkylation of a 1:1 mixture of dl- and meso-1,2-divinylethylene carbonate is reported. For the first time, both the ionization and nucleophilic addition steps of the catalytic cycle act as enantiodiscriminating steps to give a single product in high enantiomeric excess. The reactions proceed in >98% ee to efficiently generate useful chiral building blocks from acrolein. The absolute and relative configurations of iso-cladospolide B and 11-epi-iso-cladospolide B were verified by total synthesis, solving an apparent discrepancy in the literature.     

Catalytic actions of alkaline salts in reactions between 1,2,3,4-butanetetracarboxylic acid and cellulose: I. Anhydride formation

1,2,3,4-Butanetetracarboxylic acid (BTCA) reacts with cellulose in two steps: anhydride formation of adjacent carboxyl groups in BTCA and esterification of anhydride with cellulose, which are generally catalyzed by alkaline salts including sodium hypophosphite. The role of the salts in the reactions has been unclear. As an effort in fully understanding the catalytic effects of the salts, reaction mechanisms of alkaline metal ions and acid anions of the salts were investigated in details in the reactions. In this research, functions of alkaline metal ions on the formation of anhydride were studied. Results indicated that the existence of lithium, sodium or potassium promoted the formation of anhydride, and potassium ion was the most efficient one among these three ions. Besides, the reactions of a BTCA molecule with cellulose undergo a step-by-step process, i.e. formation of one anhydride and esterification of the anhydride with cellulose, and then formation of another anhydride and esterification of it to establish cross-linking by the BTCA.     

Novel aromatic tetracarboxylic acid dianhydrides

The Diels-Alder reactions of 4,4′-bis(2,4,5-triphenylcyclopentadienon-3-yl)benzophenone with carboxylic anhydrides containing multiple carbon-carbon bonds afforded novel tetracarboxylic dianhydrides. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1966–1969, October, 1999.     

Acetale von 1,2,3,4-Tetraoxobutan: Herstellung und Struktur von rac- und meso-2,3,3,4,4,5-Hexamethoxy-tetrahydrofuran

Acetals of 1,2,3,4-tetraoxobutane: preparation and structure determination of rac- and meso-2,3,3,4,4,5-hexamethoxy-tetrahydrofuran Oxidation of 3,4-dimethoxyfuran with 2 equiv. of bromine at ?75° in the presence of triethylamine and methanol leads to a mixture of rac- and meso-2,3,3,4,4,5-hexamethoxy-tetrahydrofuran (cf. Scheme 1, 4 and 5 ). The structure of the crystalline rac-compound has been determined by X-ray analysis.     

Polyimides from diamine‐acid salts and tetracarboxylic dianhydrides

Polyimides can be synthesized from a diamine‐acid salt and a dianhydride in the presence of excess triethylamine, thereby avoiding the use of air‐sensitive aromatic diamine compounds as monomers.     

内消旋和外消旋-2,3-二异丁酰氧-2,3-二苯基丁二腈的晶体结构和分子结构: 受-授取代基效应对分子构象的影响

1979年Viehe等人提出了受-授取代基效应(capto-dative substituent effect)的概念,认为在六取代乙烷(1)中,除吸电子取代基CN外,有给电子取代基R,则1比较容易均裂成取代甲基自由基2。近年来,受-授取代基效应引起了许多研究者的兴趣,但对具有受-授取代基的多取代乙烷的分子结构和晶体结构,尚鲜见报道。     

Chemical studies of potential relevance to penicillin hypersensitivity. The synthesis of dl-2-phenoxymethylpenicillenic acid and of dl-2-(2,6-dimethoxyphenyl)penicillenic acid

Crystalline samples of DL-2-phenoxy melhylpenicillenic acid ( 14 ) and of DL -2-(2, 6-dimethoxyphenyl)penicillenic acid ( 21 ) have been synthesized by the reaction of DL -penicillamine with 2 phenoxymethyl-4-(methoxymethylene)oxazol-5-one and 2-(2, 6-dimethoxyphenyl)-4-(ethoxymethylene)oxazol-5-one, respectively. These key oxazol-5-one intermediates were synthesized by azlactonization of the appropriately substituted penaldic acid dialkyl acetals. The reaction of mercury(II) chloride with D-phenoxymethylpenicillin was studied and found to be inapplicable to the synthesis of D-14 . A comparison of crystalline DL - and of amorphous D-2-(2,6-dimethoxyphenyl)penicillenic acid (21), which were prepared by the “oxazolone” and “mercury(11) chloride” methods, respectively, suggests a marked improvement in the purity of the DL -material.     

High-temperature chemical transformations of tetracarboxylic acid dianhydrides with aromatic diamines in rolivsan matrix

Russian Journal of Applied Chemistry - Thermochemical transformations of ternary thermosetting systems consisting of rolivsans, aromatic tetracarboxylic acid dianhydrides, and aromatic diamines...     

Tungstophosphoric acid catalyzed synthesis of N-sulfonyl-1,2,3,4-tetrahydroisoquinoline analogs

An operationally simple and eco-friendly protocol has been developed for the synthesis of N-sulfonyl-1,2,3,4-tetrahydroisoquinolines 3 using the modified Pictet-Spengler reaction of N-sulfonylphenylethylamines 1 and various aldehydes 2 in the presence of tungstophosphoric acid hydrate.     

Preparation of the four stereoisomers of 3-bromo-2-butanol or their acetates via lipase-catalysed resolutions of the racemates derived from dl- or meso-2,3-butanediol

The four stereoisomeric 3-bromo-2-butanols and/or their acetates were prepared via lipase-catalysed kinetic resolution by hydrolyses of the acetates of the (±)-syn- and (±)-anti-3-bromo-2-butanols, or via esterifications of the alcohols. The diastereomeric bromoacetates were obtained by syntheses from the dl- and meso-2,3-butanediols, respectively. On a preparative scale, the four stereoisomers, either as the free alcohols or as their acetates, were obtained in >95% ee, and in 35–40% yield (based on the starting racemates).     

One-pot preparation of subnanometer-sized gold clusters via reduction and stabilization by meso-2,3-dimercaptosuccinic acid

We report herein a simple method to prepare subnanometer-sized gold clusters by the reactions between hydrogen tetrachloroaurate (HAuCl4) and meso-2,3-dimercaptosuccinic acid (DMSA; HO2CCH(SH)CH(SH)CO2H) in water. It is demonstrated that DMSA molecules efficiently reduce the Au(III) species and stabilize the resultant gold clusters. The Au:DMSA clusters, which tend to aggregate into assemblages in water, can be well-isolated from each other by ion-pair formation between the carboxyl groups of DMSA and tetraoctylammonium (TOA) cations. This surface modification enables us to examine the core size distributions of the individual clusters by mass spectrometry and TEM. It is revealed that the gold clusters comprised of 10-13 atoms (ca. 0.8 nm) are the main products of the reactions.     

Bisacylation of the anhydride and esters of 4-methyl-1,2,3,4-tetrahydrophthalic acid

The bisacylation of the anhydride and esters of 4-methyl-1,2,3,4-tetrahydrophthalic acid by anhydrides of carboxylic acids in the presence of perchloric acid results in the formation of derivatives of 1,3-dialkyl-6, 7-dicarboxy-5,6,7,8-tetrahydro-2-benzopyrylium salts. Some reactions of the salts obtained, including their recyclization under the action of nucleophiles, have been studied. A convenient preparative method for the synthesis of 6,7-dicarboalkoxy-5,6,7,8-tetrahydroixoquinolines has been developed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1318–1321, October, 1984.     

Coordination compounds based on 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid

Syntheses of 2,6-bis[((3S)-3-(methoxycarbonyl)-1,2,3,4-tetrahydroisoquinolin-2-yl)carbonyl]pyridine and its coordination compounds with Cu2+, Co2+, Co3+, or Fe3+ are described. By means of 1H- and 13C-NMR spectra it was proved that 2,6-bis[((3S)-3-(methoxycarbonyl)-1,2,3,4-tetrahydroisoquinolin-2-yl)carbonyl]pyridine as well as its coordination compound with Co3+ exist in the form of a mixture of three conformers, differing in the conformations at the two amide groups present. The prepared coordination compounds were tested in the enantioselective catalysis of the nitroaldol addition of nitromethane with 2-nitrobenzaldehyde or 4-nitrobenzaldehyde, and in the Michael addition of ethyl 2-oxocyclohexanecarboxylate to but-3-en-2-one.     

1,2,3,4-Tetrahydropyrimidines and some other compounds based on propiolic acid derivatives

The reactions of ethyl propiolate and propiolamide with methylene and benzaldehyde and anisaldehyde in an acidic medium, in which the corresponding 2-oxo-1,2,3,4-tetrahydropyrimidines and 1,4-dihydropyridines or a 3,4-dihydropyrimidine derivative are formed, were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 529–531, April, 1984.     

Lipase-catalyzed kinetic and dynamic kinetic resolution of 1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid

A dynamic kinetic resolution method for the preparation of enantiopure 1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid (R)-2 was developed involving the CAL-B-catalyzed enantioselective hydrolysis of the corresponding ethyl ester (±)-1 in toluene/acetonitrile (4:1) containing 1 equiv of added water and 0.25 equiv of dipropylamine. This method allowed the preparation of (R)-2 (ee = 96%) with 80% isolated yield. The kinetic resolution of (±)-1 in diisopropyl ether at 3 °C afforded both enantiomers with ee ⩾92%.