Highly enantioselective addition of primary alkyl Grignard reagents to carbocyclic and heterocyclic arylketones in the presence of magnesium TADDOLate preparative and mechanistic aspects
作者:Beat Weber、Dieter Seebach
DOI:10.1016/s0040-4020(01)90463-6
日期:1994.1
In the presence of equimolar amounts of the Mg alkoxide from α,α,α′,α′-tetraphenyl-2,2-dimethyl-1,3-dioxolan-4,5-dimethanol (a TADDOL) primary Grignard reagents (Et, Pr, Bu, Oct, 3-butenyl) add to carbo- and heteroaromatic methyl ketones in THF at −100°C to give tertiary alcohols of enantiomeric excesses reaching values above 98%. The scope and limitation of the method are investigated. The reaction
在等摩尔量的α,α,α',α'-四苯基-2,2-二甲基-1,3-二氧戊环-4,5-二甲醇(TADDOL)伯碱试剂(Et, Pr,Bu,Oct,3-丁烯基)在-100°C下加到THF中的碳和杂芳族甲基酮中,得到对映体过量的叔醇,其值超过98%。研究了该方法的范围和局限性。在剧烈搅拌的非均质混合物中发生的反应在没有反应中心的空间位阻的情况下提供了最佳结果。由烷基溴制得的格氏试剂优于由氯化物制得的试剂。TADDOL的ee与2-苯基-2-癸醇的产品的ee之间存在完美的线性关系;那些大专绝对构型已知的醇是由酮羰基的Re面通过亲核攻击形成的。讨论了反应的立体化学过程的三种暂定机理模型。