Preparation of Chiral 3-Arylpyrrolidines via the Enantioselective 1,4-Addition of Arylboronic Acids to Fumaric Esters Catalyzed by Rh(I)/Chiral Diene Complexes

A highly efficient rhodium-catalyzed protocol for the preparation of 2-arylsuccinic esters and 3-arylpyrrolidines of high optical purity has been achieved. In the presence of 1 mol % of a chiral diene/Rh(I) catalyst, asymmetric addition of various arylboronic acids to di-<i>tert</i>-butyl fumarate (<b>3c</b>) provides the corresponding adducts in up to 99% yield and 94→99.5% ee. Excellent enantioselectivities were also observed in the regio- and enantioselective conjugate addition of phenylboronic acid (<b>4a</b>) to compound <b>3e