Efficient and Expeditious Protocols for the Synthesis of Racemic and Enantiomerically Pure Endocyclic Enecarbamates from <i>N</i>-Acyl Lactams and <i>N</i>-Acyl Pyrrolidines
作者:Denilson F. Oliveira、Paulo C. M. L. Miranda、Carlos R. D. Correia
DOI:10.1021/jo9903297
日期:1999.9.1
A mild, practical, and straightforward protocol for the construction of endocyclic enecarbamates starting from N-acyl lactams and N-acyl pyrrolidines is presented. Lactams were reduced to the corresponding alpha-hydroxycarbamates in good to excellent yields using DIBAL-H, SuperHydride, or NaBH(4) followed by beta-elimination (dehydration) promoted by trifluoroacetic anhydride in the presence of hindered
提出了从N-酰基内酰胺和N-酰基吡咯烷类开始构建内环烯氨基甲酸酯的温和,实用和直接的方案。使用DIBAL-H,SuperHyride或NaBH(4)将内酰胺以良好的优异产率还原为相应的α-羟基氨基甲酸酯(4),然后在受阻硝化碱(如2,6)的存在下,由三氟乙酸酐促进β-消除(脱水) -二甲基吡啶,二异丙基乙胺或三乙胺。该方案的微小变化允许制备几种内环烯氨基甲酸酯(12个实例),总产率良好至优异(56-96%)。已证明该方案适用于多种环大小,与不同的保护基团兼容,并且足够温和以防止易于消旋的立体中心消旋。