Imine allylation using 2-alkoxycarbonyl allylboronates as an expedient three-component reaction to polysubstituted α-exo-methylene-γ-lactams

alpha-exo-Methylene-gamma-lactams are key structural units in a wide variety of biologically active natural products. A concise route to the formation of polysubstituted alpha-exo-methylene-gamma-lactams is described. In this three-component reaction, an imine is formed from an aldehyde and ammonia in situ, and is subsequently allylated through the use of a 2-alkoxycarbonyl allylboronate. Due to the ester functionality, the addition intermediate subsequently undergoes in situ cyclization to form the observed alpha-exo-methylene-gamma-lactam products. This route allows access to highly substituted alpha-exo-methylene-gamma-lactams in moderate to excellent yields. (C) 2008 Elsevier Ltd. All rights reserved.