Direct, catalytic synthesis of carbapenams via cycloaddition/rearrangement cascade reaction: unexpected acetylenes' structure effect.

Reactions of acetylenes derived from glyceraldehyde and propargyl aldehyde show remarkable reactivity in Kinugasa cycloaddition/rearrangement cascade process catalyzed by Cu(I) ion. Reactions proceed by formation of a rigid dinuclear copper(I) complex in which each copper ion is coordinated to one or both oxygen atoms in the acetylene molecule and to both triple bonds. It has been demonstrated that one oxygen atom can be replaced by the phenyl ring, which is able to coordinate the copper ion by the aromatic sextet. Kinugasa reactions that proceed in a high yield can also be performed in the presence of a catalytic amount of the copper salt to provide products in an acceptable yield without a decrease of diastereoselectivity.