MgI2-mediated ring expansions of secondary methylenecyclopropyl amides

Ring expansion of secondary methylenecyclopropyl amides in the presence of MgI2 was investigated. Various isomeric five-membered unsaturated lactams were obtained, depending on the character of the substituent Q. The amide group served as a nucleophile in ring closing as well as an activator for ring opening. In the presence of a variety of aryl aldimines or aldehydes, alkylative ring expansion occurred in a single step under mild and neutral conditions leading to γ′-amino- or -hydroxy-alkylated pyrrol-2-ones. Also, it was shown that a 4-methylpyrrol-2-one could be transformed to a γ-hydroxy-alkylated product by the use of a direct vinylogous aldol reaction. Copyright © 2003 American Chemical Society.