Mild and efficient method for the cleavage of cyclic and acyclic ethers by iodine under solvent-free conditions

Ethers undergo smooth cleavage with acyl chlorides in the presence of a catalytic amount of elemental iodine under extremely mild conditions to give the corresponding halo esters. This new procedure offers significant advantages such as high conversions, short reaction times and enhanced selectivity together with mild reaction conditions, which makes it an attractive strategy.     

(Tosylimino)phenyl-λ3-iodane as a reagent for the synthesis of methyl carbamates via Hofmann rearrangement of aromatic and aliphatic carboxamides

A new, mild procedure for the Hofmann rearrangement of aromatic and aliphatic carboxamides using (tosylimino)phenyl-λ(3)-iodane, PhINTs, as a reagent is reported. Because of the mild reaction conditions, this method is particularly useful for the Hofmann rearrangement of substituted benzamides, which usually afford complex reaction mixtures with other hypervalent iodine oxidants. The mild reaction conditions and high selectivity in the reaction of carboxamides with PhINTs allow the isolation of the initially formed labile isocyanates or their subsequent conversion to stable carbamates by treatment with alcohols.     

Operationally simple and highly (E)-styrenyl-selective Heck reactions of electronically nonbiased olefins

Simple, mild, and efficient conditions are reported for a Pd(0)-catalyzed Heck reaction that delivers high yields and selectivity for (E)-styrenyl products using electronically nonbiased olefin substrates bearing a range of useful functionality. Preliminary mechanistic studies demonstrate that the σ-donating DMA solvent is crucial for high selectivity. Further studies suggest that the catalyst distinguishes between β-hydrogens on the basis of their relative hydridic character, in contrast to previously reported Pd(II)-catalyzed oxidative reaction conditions.     

Converting wastes into added value products: from glycerol to glycerol carbonate, glycidol and epichlorohydrin using environmentally friendly synthetic routes

Glycerol carbonate, synthesised via a non-phosgene route using glycerol and CO₂ or urea in presence of a heterogeneous catalyst, was efficiently converted into a series of derivatives through the functionalization of the -OH moiety, using high yield, high selectivity synthetic routes not affecting the carbonate functionality. So, for example, glycerol carbonate was converted into epichlorohydrin, a product that has a large industrial application, under very mild conditions, using a two-step reaction with a 98% yield and 100% selectivity. The high yield and mild reaction conditions (very often close to the ambient conditions) make the environmentally friendly synthetic approach described in this work of potential applicative interest. All compounds prepared were fully characterized.     

Triflic acid-promoted aza-Prins-Ritter reaction sequence: a novel synthesis of 4-amidopiperidine derivatives

4-Amidopiperidine derivatives have been prepared for the first time in good yields and with high selectivity by means of aza-Prins-Ritter reaction sequence using 1.2 equiv of triflic acid under mild reaction conditions.     

Alder-ene reaction of aryne with olefins

A novel intermolecular Alder-ene reaction based on aryne and olefins was developed. We performed this transformation under mild conditions such as at room temperature, and this reaction displayed high selectivity and good yields only in the presence of CsF. Hence, the intermolecular Alder-ene reaction of aryne with olefins provides an effective route to synthesize derivatives of olefins.     

Montmorillonite clay catalyzed alkylation of pyrroles and indoles with cyclic hemi-acetals

Cyclic hemiacetals such as 2-deoxy-d-ribose and 2-deoxy-d-glucose react smoothly with pyrroles and indoles on the surface of montmorillonite KSF clay under extremely mild reaction conditions to afford optically active di-pyrrolyl and bis-indolyl alkanols in good yields with high selectivity.     

HMCM-22分子筛催化1,3-苯并二噁茂烷类化合物合成的研究

研究了HMCM-22分子筛催化邻苯二酚与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、异戊醛、正己醛、正辛醛、苯甲醛、二苯甲酮等十余种醛(酮)的缩合反应.考察了反应时间、酚与醛(酮)的配比、HMCM-22分子筛用量等因素对酚与醛(酮)反应的影响.结果表明,当酚与醛(酮)摩尔比为1∶1.4,催化剂用量为3.5 g/1mol醛(酮),反应5 h,选择性一般在97%以上,转化率也一般在70%以上,表明HMCM-22分子筛对邻苯二酚与醛(酮)的反应有较好的催化性能.     

Pd-catalyzed reductive cleavage of alkyl aryl sulfides with triethylsilane that is accelerated by trialkylsilyl chloride

The palladium-catalyzed reductive cleavage of alkyl aryl sulfides to afford the corresponding arenes in high yield, which is both accelerated and exhibits increased functional group selectivity in the presence of TMSCl, is described. This ligand-free reaction features mild conditions, easy operation, use of readily available reagents, and high functional group selectivity.     

单原子催化甲烷直接转化的研究进展

将甲烷直接转化(DMC)为高附加值化学品(如甲醇等化合物),是实现天然气高效利用的有效途径.因甲烷结构非常稳定,使其在温和条件下(反应温度≤150℃的非强酸介质体系)的高效活化极具挑战性.近年来,单原子催化剂(SACs)因其活性物种的高利用率和高选择性,已引起国内外研究者的广泛关注,并被尝试应用于多种反应.研究表明,S...     

AlCl3催化作用下苯胺与CS2的反应机理初探

二苯硫脲是重要的医药和染料的中间体。常温常压下，用AlCl3作催化剂催化苯胺和CS2进行反应，可以高收率和高选择性地得到二苯硫脲。反应产物经GC／MS进行了检测，并提出了AlCl3催化苯胺和CS2的可能反应机理。     

Amphiphilic poly(oxazoline)s – synthesis and application for micellar catalysis

Homogeneous and heterogeneous catalytic processes compete on industrial scale for more then three decades [1]. The advantages of homogeneous catalysis are beside others high activity, mild reaction conditions, high selectivity and no diffusion problems. The disadvantages of such systems include difficulties with recycling of the catalyst and product separation [2].     

Heteropoly acid-catalyzed aza-Prins-cyclization: an expeditious synthesis of 4-hydroxypiperidines

4-Hydroxypiperidines are prepared in good yields and with high selectivity by means of aza-Prins-cyclization using 10 mol % phosphomolybdic acid under mild reaction conditions. This is the first report on the preparation of 4-hydroxypiperidines via aza-Prins-cyclization.     

Use of an aminosilyllithium for the diastereoselective synthesis of diphenyl oxasilacyclopentane acetals and polyols

[reaction: see text] The conjugate addition reaction of a stable, in situ generated silyllithium gives a beta-hydroxysilyl ester with high diastereoselectivity. Conversion of the beta-hydroxysilyl ester to a beta-fluorosilyl ester affords the precursor to the oxasilacyclopentane acetal in high yields under mild conditions. A hydride reduction and subsequent intramolecular silylation lead to the acetal in excellent yields. Finally, highly selective nucleophilic substitution affords oxasilacyclopentanes, which undergo a mild oxidation to afford 1,3-trans diols with high selectivity.     

Gallium iodide/iodine as a versatile reagent for the aza-Prins cyclization: an expeditious synthesis of 4-iodopiperidines

4-Iodopiperidines are prepared in good yields and with high selectivity by means of aza-Prins-cyclization using a catalytic amount of gallium(III) iodide and a stoichiometric amount of iodine under mild reaction conditions. This is the first report on the preparation of 4-iodopiperidines via aza-Prins-cyclization.     

Highly chemoselective addition of amines to epoxides in water

Aminolysis of a variety of epoxides by aliphatic and aromatic amines in water, in the absence of any catalyst with high yields, is reported. Beta-amino alcohols were formed under mild conditions with high selectivity and in excellent yields. [reaction: see text]     

Tail-to-tail dimerization of methyl acrylate in the presence of triphenylarsine ruthenium complexes

Catalytic dimerization of methyl acrylate by homogenous ruthenium catalysts was investigated. The effect of the addition of acidic additives, supporting ligands, polymerization inhibitor, and reaction conditions on the selectivity of dimerization was studied, and possible reaction mechanism was discussed. Conversion and selectivity were significantly affected by using triphenylarsine as supporting ligand. Under mild conditions, conversion up to 98% with good selectivity to tail-to-tail product was achieved.     

Study on catalytic synthesis of 1,3-benzodioxoles by HY zeolite

The acetalization and ketalization of various aldehydes and ketones with catechol by using HY zeolite as catalyst were studied. Effect of the reaction time, mole ratio of reactants, and amount of catalyst on the yield of benzodioxoles were investigated. Results show that HY is an efficient catalyst for the acetalization and ketalization with high conversion and selectivity in mild conditions. The best reaction conditions: molar ratio of catechol to aldehydes or ketones is 1:1.4, catalyst amount is 3.5 g/l mol catechol, reaction time is 5 h. Under these conditions, the conversion and selectivity were over 50% and 97%, respectively. Translated from Huaxue Tongbao 2006, 69(6) (in Chinese)     

One-Pot Synthesis of Highly Functionalized Stable Ketenimines by Three-Component Reaction of Cyclohexyl Isocyanide,Dialkyl Acetylenedicarboxylates,and Benzoyl Hydrazones

The adduct produced in the reaction between cyclohexyl isocyanide and dialkyl acetylenedicarboxylates was trapped by benzoyl hydrazones to afford highly functionalized ketenimines in good yields. The reaction is characterized by mild conditions, high selectivity, and tolerance to various functional groups.     

环糊精衍生物的点击化学合成法的研究进展

点击化学("click"chemistry)具有反应条件温和、选择性高、产率高、纯化步骤简单等优点,现已成为当前的一大研究热点.环糊精具有"内疏水、外亲水"的锥筒状空腔结构,是超分子化学的重要主体之一,合成功能各异的环糊精衍生物引起了人们的广泛关注.综述了点击反应合成环糊精衍生物的最新研究进展及其应用,并对其发展前景做了展望.