Synthesis of α-hydroxy-β,β-difluoro-γ-ketoesters via [3,3]sigmatropic rearrangements
作者:Michael J. Broadhurst、Samantha J. Brown、Jonathan M. Percy、Michael E. Prime
DOI:10.1039/b004766j
日期:——
Readily available γ,γ-difluorinated allylic alcohols obtained from trifluoroethanol were esterified efficiently. Exposure to strong base (LDA) afforded the ester enolates, in which chelation both controlled configuration and stabilised against fragmentation, which were trapped as their silyl ketene acetals. Rearrangement occurred to afford base-sensitive acid products. Esterification under mild conditions
易得的γ,γ-二氟烯丙基醇得自 三氟乙醇被有效地酯化。暴露于强大的基础(LDA)提供了 酯 烯醇盐,其中的螯合物既可控制构型,又能稳定防止碎裂,它们被捕获为甲硅烷基烯酮 缩醛。发生重排,得到碱敏酸产物。在温和的条件下进行酯化,得到可纯化的甲基酯,其中被掩盖的酮已被释放。在α位置带有苄氧基或烯丙氧基的离去物可以脱保护并释放酒类。