The Ireland–Claisen rearrangement as a probe for the diastereoselectivity of nucleophilic attack on a double bond adjacent to a stereogenic centre carrying a silyl group
作者:Mark S. Betson、Ian Fleming
DOI:10.1039/b305881f
日期:——
4-R-4-dimethyl(phenyl)silylbut-2-enyl acetate (R = Me and Pr(i)) undergo Ireland-Claisen rearrangements largely in the same stereochemical sense, with C-C bond formation taking place anti to the silyl group in the conformations 22, 23 and 24 in which the hydrogen atom on the stereogenic centre is inside, more or less eclipsing the double bond. The E-silyl enol ether E-7a derived from 4-methyl-4-dimethyl(phenyl)silylbut-2-enyl
衍生自3-R-3-二甲基(苯基)甲硅烷基丙酸烯丙酯(R = Me,Pr(i)和Ph)的E-和Z-甲硅烷基烯醇醚4和衍生自4-R-的Z-甲硅烷基烯醇醚7 4-二甲基(苯基)甲硅烷基丁-2-烯基乙酸酯(R = Me和Pr(i))在很大程度上以相同的立体化学方式经历Ireland-Claisen重排,其中CC键的形成与甲硅烷基的构象相反22图23和24中立体中心的氢原子在内部,或多或少地掩盖了双键。衍生自4-甲基-4-二甲基(苯基)甲硅烷基丁-2-烯基乙酸酯的E-甲硅烷基烯醇醚E-7a在另一种意义上显示出较低的非对映选择性,这可能是因为CC键的形成与构象中的甲硅烷基相反里面有甲基26 但是,从4-异丙基-4-二甲基(苯基)甲硅烷基丁-2-烯基乙酸酯衍生的甲硅烷基烯醇醚E-7b在正常情况下显示出较低的非对映选择性。衍生自顺丁烯丙基3-苯基-3-二甲基(苯基)甲硅烷基丙酸酯的E-和Z-甲硅烷基烯醇醚