Diastereocontrol in open-chain nucleophilic attack on a double bond adjacent to a stereogenic centre carrying a silyl group
作者:Mark S. Betson、Ian Fleming、Jacqueline V. A. Ouzman
DOI:10.1039/b305882d
日期:——
selectivity is low (58:42) in the first case 11, where the nucleophilic attack is adjacent to the stereogenic centre carrying the silyl group, and moderate (72:28) for both Z- and E-alpha,beta-unsaturated esters 14 and 15, where the nucleophilic attack is at the other end of the double bond from the stereogenic centre. It is conceivable that nucleophilic attack actually takes place in a conformation in which
双[二甲基(苯基)甲硅烷基] cup酸酯试剂将甲硅烷基引入三个α,β-不饱和酯的β-位置:甲基Z-4-二甲基(苯基)甲硅烷基戊-2-烯酸酯11和甲基Z-和E-(1'-二甲基苯基甲硅烷基苄基)丁-2-烯酸酯14和15在意想不到的意义上非对映地选择性,与氢原子在“内部”的构型的甲硅烷基基团相同。在第一种情况11中,选择性低(58:42),亲核攻击与带有甲硅烷基的立构中心相邻,对Z-和E-α,β-不饱和酯的选择性中等(72:28)参照图14和15,其中亲核攻击是在立体异构中心的双键的另一端。可以想象亲核攻击实际上是在一种构象中发生的,其中供体取代基,