Relay Catalysis Using a Rhodium Complex/Chiral Brønsted Acid Binary System: Enantioselective Reduction of a Carbonyl Ylide as the Reactive Intermediate

Pass the baton: A one-pot relay catalysis for a carbonyl ylide formation/enantioselective reduction sequence using a dirhodium(II) tetracarboxylate and chiral phosphoric acid catalyst system is described. The four-step transformation involves a rhodium carbene complex, a carbonyl ylide, and an isobenzopyrylium intermediate, the enantioselective reduction of which yields isochromanone derivatives in good yield with high selectivity.