Diastereoselective synthesis of pyrrolidines via the Yb(OTf)3 catalyzed three-component reaction of aldehydes, amines, and 1,1-cyclopropanediesters

[Chemical reaction: see text] Aldimines, generated in situ by the reaction of primary amines or anilines with aldehydes, undergo smooth reaction with various 1,1-cyclopropanediesters in the presence of catalytic Yb(OTf)3. The products are pyrrolidines in which the major diastereomer bears a cis relationship between substituents at the 2- and 5-positions. In most cases the diastereoselectivity is greater than 10:1.