Selective hydrogenation of unsaturated carbon-carbon bonds with rhodium complexes

Abstract

When mixtures of unsaturated substances, or compounds containing multiple sites of unsaturation are hydrogenated using RhCl(PPh₃)₃ as catalyst, it is possible that the substrate which reduces slowest as a single substrate can be hydrogenated preferentially in the mixture. The degree of selectivity achieved can be enhanced by the addition of polar solvents, the effects of which are discussed. The degree of participation of the two kinetically indistinguishable forward routes, i.e., via substrate attack on a hydrido intermediate, or hydrogen attack on a substrate intermediate, may also be of importance in determining the degree of selectivity achieved.