Asymmetric hydrogenation of α-ethylstyrenes catalyzed by chiral ruthenium complexes

A combined system of RuCl2[(R,R)-Me-DuPhos](dmf)n and t-C4H9OK catalyzes the asymmetric hydrogenation of α-ethylstyrene derivatives. The reaction proceeds with a substrate to catalyst molar ratio of up to 2600 in 2-propanol at 8 atm and room temperature to give the chiral saturated products in 81–89% ee.