The diastereoselectivity of electrophilic attack on trigonal carbon adjacent to a stereogenic centre: diastereoselective alkylation and protonation of open-chain enolates having a stereogenic centre at the ? position
作者:Ian Fleming、Jeremy J. Lewis
DOI:10.1039/p19920003257
日期:——
and protonation of the enolates 10, 27, 31 and 36 are diastereoselective in conformity to a general rule, summarised in the drawing 1, governing the stereochemistry of electrophilic attack on a double bond adjacent to a stereogenic centre. The sense of the selectivity is, with one exception, opposite to that of the corresponding nucleophilic attack on a carbonyl group adjacent to a stereogenic centre
的烯醇化物的甲基化7,24,28和33和质子化的烯醇化物的10,27,31和36是在符合一般规则非对映选择性,在图形总结1,治电攻击的立体化学上的双键相邻立体感中心。选择性的感觉与在立体定向中心附近的羰基上的相应亲核攻击的感觉相反,在另一个方面,它遵循克拉姆法则和费金-安赫规则,其总结见图2。。例外情况可能是减少量40 → 38 + 39,其中39是主要乘积。如果将异丙基计算为比苯基“大”,则该结果与克拉姆法和费尔金-安赫法则不一致,而格利雅反应37 → 38 + 39,其中39仍然是主要产物,以及相应的亲电反应33 → 34 + 35,其中34为主要产品,36 → 34 + 35,其中35为主要产品 作为主要产品,均与异丙基有效地大于苯基一致。