Ring Expansions of 2-Alkenylazetidinium Salts – a New Route to Pyrrolidines and Azepanes
作者:François Couty、François Durrat、Gwilherm Evano、Jérome Marrot
DOI:10.1002/ejoc.200600362
日期:2006.9
Series of enantiomerically pure 3-alkenylpyrrolidines, substituted azepanes and stereodefined aminoalkenes were synthesized from 2-alkenylazetidinium trifluoromethanesulfonate salts. The high chemoselectivity of these reactions was found to be strongly dependent both on the nature of the base involved in the process (PhLi or KHMDS) and on the relative cis or trans stereochemistry of the intermediate
从 2-烯基氮杂鎓三氟甲磺酸盐合成了一系列对映体纯 3-烯基吡咯烷、取代的氮杂环庚烷和立体定义的氨基烯烃。发现这些反应的高化学选择性强烈依赖于该过程中所涉及的碱(PhLi 或 KHMDS)的性质以及中间体叶立德铵的相对顺式或反式立体化学。当叶立德和相邻的烯烃是反式时,[1,2] σ 移位仅发生,产生具有高水平区域选择性的吡咯烷。另一方面,当这两个基团处于顺式关系时,观察到通过 [2,3] sigmatropic 转移干净地转化为 4,5-脱氢氮杂环庚烷。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany , 2006)