Synthesis of Chiral trans-Epoxides

Significance

A general, asymmetric route to various trans-epoxides is presented by the authors. The key step to enantioselectivity is an asymmetric, organocatalytic α-chlorination of aldehydes with prolinamide (1). Subsequently, addition of organolithium reagents to α-chloro aldehyde 2 with good to excellent diastereoselectivities (dr = 8:1 up to 20:1) and epoxide formation leads in direct sequence to alkynyl-, trans-alkenyl-, cis-alkenyl-, phenyl-, and alkyl-substituted trans-epoxides. This methodology, completed by Lindlar reduction of diynes, was applied in a three-step synthesis of trans-epoxide-containing insect sex pheromones isolated from female pine looper moth Bupalus piniarius (3) and female tussock moth Orgyia postica (4).