Ligand Design for Rh(III)-Catalyzed C-H Activation: An Unsymmetrical Cyclopentadienyl Enables a Regioselective Synthesis of Dihydroisoquinolones.

We report the regioselective synthesis of dihydroisoquinolones from aliphatic alkenes and -pivaloyl benzhydroxamic acids mediated by a Rh(III) precatalyst bearing sterically bulky substituents. While the prototypical Cp* ligand provides product with low selectivity, sterically bulky Cp affords product with excellent regioselectivity for a range of benzhydroxamic acids and alkenes. Crystallographic evidence offers insight as to the source of the increased regioselectivity.