Claisen rearrangement of N-silyl ketene N,O-acetals generated from allyl N-phenylimidates
作者:Peter Metz、Cornelia Linz
DOI:10.1016/s0040-4020(01)89670-8
日期:1994.3
O-acetals 5 which undergo a Claisen rearrangement to yield γ,δ-unsaturated anilides 3 after hydrolytic work-up. The temperature for the rearregement step is dependent on the nature of the substituent R2 in 5. Ketene acetals 5 with R2 = H rearrage readily at room temperature, while heating at 130 °C is required if R2≠H. The degree of simple diastereoselection attainable for the conversion of 1 to 3 is strongly
烯丙基N-苯基亚氨酸酯1的去质子化和随后的N-甲硅烷基化导致N-甲硅烷基烯酮N,O-乙缩醛5经过水解后进行克莱森重排,以产生γ,δ-不饱和的酸酐3。用于rearregement步骤的温度依赖于取代基R的性质2在5。室温下,R 2 = H重排的乙缩醛5,如果R 2 ≠H,则需要在130°C加热。从1转换为3可获得的简单非选择性选择度取代基R 4的大小强烈地影响R 2。当R 4 > H时,通过船形过渡态有效抑制重排途径可导致优异的抗/顺式选择性。从几个烯丙基N-苯基亚氨酸酯和N-甲硅烷基烯酮N,O-缩醛获得的NOE差异数据支持了这一原理。