Reactivity of the Carbocations Stabilized by Divalent Sulfur and Application to Organic Synthesis

提出了一种新的分离硫稳定碳阳离子1，3-二硫杂环-2-钇和1，3-二硫杂环-2-钇离子作为盐的新方法，并将分离出的盐转化为烯酮二硫代缩醛和原酯。这些盐与硫醇和亚硫酸盐等亲核试剂反应生成加合物，作为光化学反应生成二硫代碳正离子的前驱体。对分离的盐在水溶液中的反应进行了动力学研究，并提出了四面体中间体破裂的详细机理。混合O，S-邻酯的水解也为四面体中间体的分解机理提供了有用的信息。对二硫代缩酮缩醛的酸催化水解动力学研究表明，二硫代碳正离子中间体容易去质子化，即质子化是可逆的。用氙灯对2-(对甲苯磺酰基)-1，3-二硫杂环戊烷和2-(对氯苯硫基)-1，3-二硫杂环戊烷及其2-苯基衍生物的水溶液进行了闪光光解。用MCPD检测器快速扫描的紫外光谱表明，过渡中间体是二硫代锂离子。瞬时阳离子的衰减曲线比预期的一级衰减和阳离子的复合更快，形成的反阴离子被认为对反应有贡献。在硫醇或亚硫酸盐存在下，阳离子的衰减遵循一级动力学，得到了与亲核试剂反应的二级速率常数，并计划进一步测定各种亲核试剂和碳正离子的反应速率常数。

A new simple method for isolation of sulfur-stabilized carbocations, 1,3-dithiolan-2-ylium and 1,3-dithian-2-ylium ions, as salts was presented, and the isolated salts were converted to ketene dithioacetals and ortho esters. Reactions of the salts with nucleophiles, such as thiols and sulfinates afforded adducts, which were used as precursors for photochemical generation of dithio carbocations.Reactions of the isolated salts in aqueous solution were kinetically examined and a detailed mechanism of the breakdown of the tetrahedral intermediate was presented. Hydrolysis of Mixed O,S-ortho esters also provided useful information on the mechanism of the breakdown of the tetrahedral intermediate.Kinetic investigations on the acid-catalyzed hydrolysis of ketene dithioacetals showed that the dithio carbocation intermediates easily deprotonate; i. e., the protonation is reversible. Effects of an internal hydroxyl group on the hydrolysis of ketene dithioacetal resulted in a discovery of a new mode of anchimeric assistance; an internal solvation mechanism.Flash photolysis was carried out with a xenone lamp on aqueous solutions of 2-(p-toluene-sulfonyl)-1, 3-dithiolane and 2-(p-chlorophenylthio)-1,3-dithiolane, and their 2-phenyl derivatives. UV spectra, rapidly scanned with an MCPD detector, showed that the transient intermediate is dithiolanylium ion. Decay curves of the transient cation were more rapid than those expected for the first-order decay and recombination of the cation and the counter anions formed was considered to contribute to this reaction. In the presence of thiol or sulfinate, the decay of the cation followed the first-order kinetics and the second-order rate constants for the reactions with the nucleophiles were obtained.Further determinations of rate constants for reactions of a variety of nucleophiles and carbocations are planned.