Epimerization and kinetic resolution in copper-catalyzed enantioselective 1,4-additions of organozinc reagents to 6-substituted cyclohex-2-enones
作者:Laura Mediavilla Urbaneja、Alexandre Alexakis、Norbert Krause
DOI:10.1016/s0040-4039(02)01898-1
日期:2002.10
Enantioselective 1,4-addition reactions of diethyl-, dimethyl-, and di-n-butylzinc to 6-methylcyclohex-2-enone (1) and 6-t-butylcyclohex-2-enone (4), catalyzed by Cu(OTf)2 and phosphoramidites L1–L4 were examined. The additions to enone 1 proceeded with high enantioselectivity; by acid- or base-catalyzed epimerization, adduct (S,S)-2 can be obtained from racemic 1 in diastereo- and enantiomerically
Cu(OTf)催化二乙基,二甲基和二正丁基锌与6-甲基环己-2-烯酮(1)和6-叔丁基环己-2-烯酮(4)的对映选择性1,4-加成反应)2和亚磷酰胺L1 - L4进行了检查。对烯酮1的添加以高对映选择性进行。通过酸或碱催化的差向异构化,可以从外消旋体1获得非对映体和对映体纯形式的加合物(S,S)-2。相比之下,迈克尔在底物4上的添加 速度很慢,可以用于烯酮的动力学拆分。