C-H Functionalization/Asymmetric Michael Addition Cascade Enabled by Relay Catalysis: Metal Carbenoid Used for C-C Bond Formation

A combination of either ruthenium(II) or rhodium(II) complexes and quinine-derived squaramide enables 3-diazooxindoles, indoles, and nitroalkenes to undergo highly efficient asymmetric three-component reactions, thus affording optically active 3,3'-bis(indole)s through a consecutive C-C bond-forming sequence, which turned out to be applicable to the facile total synthesis of (-)-folicanthine.