Rhodium/Chiral-Diene-Catalyzed Switchable Asymmetric Divergent Arylation of Enone-Diones.

Abstract

A rhodium/chiral diene catalytic system is reported for the reaction of enone-diones and arylboronic acids that allows the switchable synthesis of chiral bicyclic products and acyclic products in a controlled manner. The production of bicyclic products containing four contiguous stereocenters is assumed to proceed through the enantioselective arylrhodation of enone-diones with Cs2CO3, forming a rhodium-enolate intermediate, followed by desymmetrization of the diastereotopic diones via aldol cyclization with quantitative diastereoselection and excellent enantiomeric excess. The production of acyclic products is assumed to proceed through the enantioselective hydroarylation of enone-diones with excellent enantiomeric excess in which the aldol cyclization is significantly inhibited by the choice of Et3N as a base. The selectivity for bicyclic products (via tandem arylation-aldol cyclization) and acyclic products (via hydroarylation) is rationalized by the proposed model.