Palladium(II)-catalyzed asymmetric synthesis of (Z)-alpha-alkylidene-gamma-butyrolactams from (Z)-N-allylic 2-Alkynamides. Total synthesis of (-)-isocynometrine

Abstract

Pd(OAc)2 combined with nitrogen-containing ligands catalyzed the cyclization of (Z)-N-allylic 2-alkynamides in acetic acid to afford the alpha-(Z)-acetoxyalkylidene-gamma-butyrolactams in high yield and high stereoselectivity. When chiral nitrogen-containing ligands were used, the catalytic asymmetric protocol was achieved with moderate enantioselectivity (up to 80 degrees C). The utility of this new methodology was exemplified by the total synthesis of (-)-isocynometrine.