Evans手性助剂控制的不对称Michael加成立体选择性研究(Ⅱ)

Asymmetric Michael Addition Reaction under the Control of the Evans Chiral Auxiliary (Ⅱ)

手性助剂控制的不对称反应是不对称合成的重要方法之一.以Evans手性助剂控制的Michael受体1为底物,在FeCl3催化下,通过不同格式试剂对其进行Michael加成,一步反应得到了一系列含两个手性中心的Michael加成产物2a～2h.获得了较高的立体选择性,其中化合物2d和2e得到了de值高达98%的非对映选择性.研究结果表明,亲核试剂的空间位阻是影响产物立体选择性的主要因素.

Chiral auxiliaries controlled asymmetric reaction is one of the main methods in asymmetric synthesis.Under the control of the Evans auxiliary and catalyzed by FeCl3,different Grignard reagents were added asymmetrically to the substrates 1 by the way of 1,4-Michael addition reaction,and a series of Michael addition products 2a～2h which containing two chiral centers have been synthesized with higher stereoselectivity.Among them,compounds 2d and 2e achieved high diastereospeci-fically up to 98% de.The results showed that the steric hindrance of the Grignard reagents is the main factor which influences the stereoselectivity of Micheal addition.