Abstract
A highly regio- and stereoselective synthesis of 3,3-disubstituted phthalides from aryl carboxylic acids and allenes using a rhodium(III) catalyst has been demonstrated. The reaction features broad functional group tolerance and provides a simple and straightforward route to the synthesis of various 3-vinyl-substituted phthalides. Furthermore, the catalytic reaction can also be applied to the synthesis of biologically active 5-vinyl-substituted 2-furanones from ?,?-unsaturated carboxylic acids and allenes. The reactions proceed through a carboxylate-assisted ortho-C-H activation and [4+1] annulation. The preliminary mechanistic studies suggest that a C-H cleavage is the rate-determining step.