硫叶立德[2,3]-σ重排反应迁移基团活性研究

Studies on the Reactivity of Migrating Group in [2,3]-Sigmatropic Rearrangement of Sulfur Ylides

设计并完成了过渡金属铑、铜化合物等的催化下,苯基重氮乙酸乙酯与不同硫醚的硫叶立德[2,3]-σ重排反应.通过1H NMR方法测定混合产物的比例,比较烯丙基、炔丙基与联烯基等不同取代硫醚的反应活性,得到这些迁移基团在硫叶立德[2,3]-σ重排反应中的竞争顺序,以及不同类型催化体系对反应的影响.实验结果为进一步理解和应用该反应提供数据支持.

The [2,3]-sigmatropic rearrangement of sulfur ylides is unique and useful reaction in organic synthesis. In this study, the reactivity of sulfides containing three different migrating groups （propargyl, allyl, and allenyl） in [2,3]-sigmatropic rearrangement of sulfur ylides has been compared. The competition reactions of phenylethyldiazoacetate with sulfides through sulfonium ylide [2,3]-sigmatropic rearrangement are designed under Rh（II）- or Cu（I）-catalyzed reaction conditions. Both intra- and intermolecular competitions of sulfides bearing two different migrating groups have been carried out. The ratio of products has been determined by IH NMR in order to compare the reactivity of different sulfides bearing allyl, pro- pargyl or allenyl groups. Obvious disparity of the reactivity of these sulfides in [2,3]-sigmatropic rearrangement has been observed. Experimental data indicate that the tendency of preferential [2,3]-sigmatropic rearrangement has the following order： propargyl sulfide〉allyl sulfide〉allenyl sulfide. Catalysts such as Rh2（OAc）4, Rh2（O2CCF3）4, and Cu（CH3CN）4PF6 ligated with a series of diimine ligands have been investigated for these reactions. Rh（II） complexes are found more efficient than Cu（I） complexes, and Rh2（O2CCF3）4 is more efficient than Rh2（OAc）4. The efficiency of different catalytic system has been explained based on the proposed reaction mechanism. The reaction catalyzed by Rh（II） complexes is suggested to be different from that catalyzed by Cu（I） complexes. In the＇case of Cu（I）-catalyzed reaction, Cu（I）-bonded,sulfur ylide is con- sid^red as the predominant intermediate, while the [2,3]-sigmatropic rearrangement is suggested to proceed through free ylide. Both steric hindrance and electronic properties of ligands influence the ratio and selectivity in Cu（I）-catalyzed reactions. This study provides useful information for fiLrther investigation of [2,3]-sigmatropic rearrangement of sulfur ylides.