Stereoselective formation of allylic sulfides via two sequential (3,3)-sigmatropic rearrangements of allylic xanthates and its mechanistic aspects.
作者:Kazunobu HARANO、Norihide OHIZUMI、Keisuke MISAKA、Shigeru YAMASHIRO、Takuzo HISANO
DOI:10.1248/cpb.38.619
日期:——
O-(2-Alkynyl) S-alkyl dithiocarbonates (allylic xanthates) were pyrolyzed to give 2-alkenyl alkyl sulfides (allylic sulfides) via the corresponding allylically isomeric S-(2-alkenyl) S-alkyl dithiocarbonates. The reaction follows the first-order rate law with relatively low sensitivity to the ionizing power of the medium and sizeably negative entropies of activation. When a mixture of two dithiol esters having different S-(2-alkenyl) groups and different S-alkyl groups was pyrolyzed, a "cross product" was not observed. The reaction was found to be facilitated by the presence of phenolic compounds or Lewis acids.Based on these findings together with modified neglect of diatomic overlap (MNDO) calculation data, the mechanism for the formation reaction of 2-alkenyl alkyl sulfides is discussed.
O-(2-炔基) S-烷基二硫代碳酸酯(烯丙基黄原酸酯)通过相应的烯丙异构S-(2-烯基) S-烷基二硫代碳酸酯,热解生成2-烯基烷基硫醚(烯丙基硫醚)。该反应遵循一级速率定律,对介质的电离能力相对不敏感,并且活化熵显著为负。当含有不同S-(2-烯基)基团和不同S-烷基基团的两种二硫酯混合物进行热解时,未观察到“交叉产物”。发现反应在酚类化合物或路易斯酸的存在下得到促进。基于这些发现以及改进的原子间重叠忽略(MNDO)计算数据,讨论了2-烯基烷基硫醚生成反应的机理。