Elevated Catalytic Activity of Ruthenium(II)-Porphyrin-Catalyzed Carbene/Nitrene Transfer and Insertion Reactions with N-Heterocyclic Carbene Ligands

Bis(NHC)ruthenium(II)-porphyrin complexes were designed, synthesized, and characterized. Owing to the strong donor strength of axial NHC ligands in stabilizing the trans MCRR/MNR moiety, these complexes showed unprecedently high catalytic activity towards alkene cyclopropanation, carbene CH, NH, SH, and OH insertion, alkene aziridination, and nitrene CH insertion with turnover frequencies up to 1950min(-1). The use of chiral [Ru(D-4-Por)(BIMe)(2)] (1g) as a catalyst led to highly enantioselective carbene/nitrene transfer and insertion reactions with up to 98%ee. Carbene modification of the Nterminus of peptides at 37 degrees C was possible. DFT calculations revealed that the trans axial NHC ligand facilitates the decomposition of diazo compounds by stabilizing the metal-carbene reaction intermediate.