Asymmetric Thio-Claisen Rearrangement Induced by an Enantiopure Alkylsulfinyl Group. Unusual Preference for a Boat Transition State in the Acyclic Series
作者:Stéphanie Nowaczyk、Carole Alayrac、Vincent Reboul、Patrick Metzner、Marie-Thérèse Averbuch-Pouchot
DOI:10.1021/jo015956m
日期:2001.11.1
vinylic alkylsulfinyl substituent were readily prepared from (R)-2-cyclohexylsulfinyl-N,N-dimethylethanethioamide 1 with full control of the geometry of their double bonds. They underwent a Claisen rearrangement upon heating at THF reflux to afford alpha-sulfinyl gamma-unsaturated thioamides 3a-c and 6a-b. With all substrates the asymmetric induction of the sulfinyl group was excellent. The determination
由(R)-2-环己基亚磺酰基-N,N-二甲基乙硫酰胺1容易制得带有对映体纯净的乙烯基烷基亚磺酰基取代基的烯氨基硫缩醛2a-c和5a-b,并完全控制其双键的几何形状。当在THF回流下加热时,它们进行克莱森重排,得到α-亚磺酰基γ-不饱和硫代酰胺3a-c和6a-b。对于所有底物,亚磺酰基的不对称诱导都非常好。硫代酰胺3a-c和6a-b的绝对构型的确定是通过X射线晶体学分析或化学相关性完成的。这种[3,3]σ转位的立体化学过程由电子模型解释。有趣的是,(ZE)-肉桂基底物5b的克莱森重排显示为通过船形过渡状态而不是椅子过渡状态。这样的偏好对于非循环系统而言是非常不寻常的。