(-)-8-Phenylmenthol was used as a chiral auxiliary to direct asymmetric reactions of its preformed carboxylates. Reduction of xanthates la and Ib by SmI2 likely proceeded via HMPA-bound samarium enolate intermediates. Self- and cross-pinacolic coupling reactions of 8-phenylmenthyl alpha-oxoesters were achieved in a highly stereoselective manner by treatment with SmI2 at -78 degrees C. The stereochemical outcome was consistent with a chelated mode of transition states. (C) 2000 Elsevier Science Ltd. All rights reserved.
(-)-8-苯基薄荷醇被用作手性辅助剂,用于指导其预先形成的
羧酸酯的不对称反应。
色烷酸酯la和Ib在
SmI2的还原作用下,可能通过HMPA稳定的
钐(samarium)烯醇式(enolate)中间体进行反应。在-78°C下,8-苯基薄荷基α-
酮酯与 反应,实现了自偶联和交叉偶联反应,且具有高度的立体选择性。其立体
化学结果与过渡态的螯合模式一致。©2000 Elsevier Science Ltd. 保留所有权利。