Radical-chain reductive alkylation of electron-rich alkenes mediated by silanes in the presence of thiols as polarity-reversal catalysts
作者:Hai-Shan Dang、Mark R. J. Elsegood、Kyoung-Mahn Kim、Brian P. Roberts
DOI:10.1039/a903961i
日期:——
triphenylsilanethiol as catalysts (5–10 mol% based on alkene). In the presence of the thiol, the slow direct abstraction of hydrogen from the silane by the nucleophilic adduct radical R1R2ĊCH2R3 is replaced by a cycle of more rapid polarity-matched reactions in which hydrogen-atom transfer to the adduct radical from the thiol is followed by abstraction of hydrogen from the silane by the derived thiyl radical, to regenerate
在硫醇催化剂的存在下,三苯基硅烷通过亲电子的碳中心自由基R 3 media,通过有机卤化物R 3 Hal介导富电子的末端烯烃R 1 R 2 C CH 2的还原烷基化。反应在苯或二恶烷溶剂中,使用亚硝酸二叔丁酯(在60°C时)或过氧化二月桂酰过氧化物(在80°C时)作为引发剂,并获得良好的加合物R 1 R 2 CHCH 2 R 3收率。用巯基乙酸甲酯或三苯甲硫醇作为催化剂(基于烯烃,为5-10摩尔%)制得。中的巯基,氢从硅烷通过亲核加成物缓慢直接抽象的存在基团R 1 - [R 2 CCH 2 - [R 3是通过更快速极性匹配的反应的循环置换,其中氢原子转移到加合物从硫醇产生的自由基之后,是通过衍生的噻吩基从硅烷中夺取氢,以再生催化剂。在不存在硫醇的情况下,还原烷基化产物的产率可忽略不计。同手性硫醇,1-硫代-β - D-甘露吡喃糖四乙酸酯和1-硫代-β - D-葡吡喃糖四乙酸盐,后者的四新戊