Asymmetric Syntheses with the Aid of Homogeneous Transition Metal Catalysts

The progress made in the field of homogeneous catalysis during the last five to six years has led, inter alia , to the development of highly selective catalysts for asymmetric syntheses. Homogeneous asymmetric hydrogenation, using well defined transition metal catalysts, may be achieved with optical yields of 85 to 90% or more. Catalytic reactions, in which the chiral centers are generated by CC bond formation, can result in optical yields of 70 to 80%. The hydrogenation catalysts consist primarily of rhodium(I) complexes containing “Homer phosphanes”, phosphanes with chiral C atoms, or optically active amides. Catalysts which induce optical activity through the formation of CC bonds have been developed from π‐allylnickel halides, Lewis acids, and phosphanes containing chiral C atoms. The results obtained signify a breakthrough in an area of catalysis previously restricted to syntheses involving enzymes.