Premium
Ring Expansions of 2‐Alkenylazetidinium Salts – a New Route to Pyrrolidines and Azepanes
Author(s) -
Couty François,
Durrat François,
Evano Gwilherm,
Marrot Jérome
Publication year - 2006
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200600362
Subject(s) - chemistry , ylide , sigmatropic reaction , chemoselectivity , regioselectivity , alkene , pyrrolidine , trifluoromethanesulfonate , ring (chemistry) , medicinal chemistry , ammonium , carbene , formamides , organic chemistry , stereochemistry , catalysis
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 ammonium ylide. When the ylide and the adjacent alkene are trans , a [1,2] sigmatropic shift occurs exclusively, producing a pyrrolidine with high levels of regioselectivity. On the other hand, clean conversion into 4,5‐dehydroazepanes through a [2,3] sigmatropic shift is observed when these two groups are in a cis relationship.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)