Brønsted Acid Differentiated Metal Catalysis by Kinetic Discrimination

Significance

In recent years, increased attention is given to the combination of organo- and transition-metal catalysis. In this paper, the authors ­utilize this concept on the example of the first Brønsted acid differentiated metal-catalyzed hydrogenation by kinetic discrimination. The catalytic system consists of an achiral iridium(III)-diamine complex and a chiral N-triflylphosphoramide. The formation of two diastereomeric ion pairs was postulated, with one being considerably more active than the other. The extended substrate scope was screened using enantiopure components at lowered temperature (66-98% yields, 92:8 to 97:3 er).