A Planar-Chiral Rhodium(III) Catalyst with a Sterically Demanding Cyclopentadienyl Ligand and Its Application in the Enantioselective Synthesis of Dihydroisoquinolones

The rapid development of enantioselective C-H activation reactions has created a demand for new types of catalysts. Herein, we report the synthesis of a novel planar-chiral rhodium catalyst [(C5H2Bu2CH2Bu)-Bu-t-Bu-t)RhI2](2) in two steps from commercially available [(cod)RhCl](2) and tert-butylacetykne. Pure enantiomers of the catalyst were obtained through separation of its diastereomeric adducts with natural (S)proline. The catalyst promoted enantioselective reactions of aryl hydroxamic acids with strained alkenes to give dihydroisoquinolones in high yields (up to 97%) and with good stereoselectivity (up to 95 % ee).