Iridium-catalyzed enantioselective hydrogenation of olefins

Cationic iridium complexes with chiral P,N-ligands and tetrakis[3,5-(trifluoromethyl)phenyl]borate (BArF) as the counterion are efficient homogeneous catalysts for the enantioselective hydrogenation of olefins. The complexes are readily prepared, air-stable, and easy to handle. In contrast to chiral rhodium- and ruthenium-phosphine catalysts, they do not require the presence of a polar coordinating group near the C=C bond. In the hydrogenation of unfunctionalized arylolefins, high enantioselectivities of > 95% ee with turnover numbers of up to 5000 and turnover frequencies of > 5000 h(-1) have been achieved. 1 Introduction 2 Initial Experiments 3 Catalyst Optimization: an Unexpected Anion Effect 4 Practical Aspects 5 Survey of Chiral Ligands 6 Survey of Reactions 7 Conclusion.