Enantioselective Catalysis with Transition Metal Compounds
Prochiral olefins, imines, and ketones can be reduced enantioselectively using optically active transition metal catalysts. With this concept, a small amount of an optically active catalyst is sufficient to produce a large amount of an optically active product, corresponding to a multiplication of the chiral information contained in the catalyst. The different reduction variants, hydrogenation with gaseous H2, transfer hydrogenation, hydrosilylation, etc., are compared. The scope of the substrates as well as the enantioselective catalysts is discussed. An example is the enantioselective hydrosilylation of acetophenone with diphenylsilane which gives α-phenylethanol in close to 100% ee after hydrolysis. The development of new enantioselective catalysts and the extension of the concept of enantioselective catalysis to new organic reactions will be presented.