trans-Directing Ability of the Amide Group: Enabling the Enantiocontrol in the Synthesis of 1,1-Dicarboxy Cyclopropanes. Reaction Development, Scope, and Synthetic Applications
journal contributionposted on 04.12.2009, 00:00 by David Marcoux, Sébastien R. Goudreau, André B. Charette
In this article, we describe our efforts toward the enantioselective formation of 1,1-cyclopropane diesters via the metal-catalyzed cyclopropanation of olefins. The strategies envisioned to achieve such a goal are discussed as well as the results that led us to the discovery of the powerful trans-directing ability of the amide group in Rh(II)-catalyzed cyclopropanation reactions. We show how this feature enables a solution for the stereoselective synthesis of 1,1-dicarboxy cyclopropane derivatives. The scope and limitations are discussed as well as the demonstration that these newly formed cyclopropanes display reactivity similar to that of 1,1-cyclopropane diesters. Conversely, 1,1-cyclopropane diesters could be accessed in two steps from commercially available alkenes. The potential utility of this methodology is illustrated by several functional group transformations and its use in the expedient stereoselective formal synthesis of (S)-(+)-curcumene, (S)-(+)-nuciferal, (S)-(+)-nuciferol, (+)-erogorgiaene, (±)-xanthorrhizol, and (±)-2-hydroxycalamenene.