Synthesis of substituted tetrahydropyridines by cyclizations of silicon-containing iminium ions
作者:G.William Daub、Dirt A. Heerding、Larry E. Overman
DOI:10.1016/s0040-4020(01)86645-x
日期:1988.1
stereoselectively from the cyclization of silicon-containing iminium cations 5 if the nitrogen substituent R1 is an alkyl group. In contrast, cyclization of the corresponding NH or N-acyl iminium ions occurs in a stereorandom fashion. Nonracemic tetrahydropyridines cannot be prepared in this way, since both iminium ion and N-acyliminium ion intermediates racemize prior to cyclization.
如果氮取代基R 1为烷基,则由含硅的亚胺阳离子5的环化立体选择性地形成反式2,6-二取代-1,2,5,6-四氢吡啶。相反,相应的NH或N-酰基亚胺离子的环化以立体随机方式发生。无法以这种方式制备非外消旋的四氢吡啶,因为亚胺离子和N-酰基亚胺离子中间体都在环化之前消旋。