Asymmetric hydroformylation of conjugated dienes catalyzed by chiral phosphine-phosphite-Rh(I) complex

Asymmetric hydroformylation of conjugated dienes has been investigated using (R,S)-BINAPHOS-Rh(I) complex as a catalyst [(R,S)-BINAPHOS = (R)-2-(diphenylphosphino)- 1,1' binaphthalen-2'-yl (S)-1,1'-binaphthalene-2,2'-diyl phosphite]. Optically active beta,gamma-unsaturated aldehydes were obtained in high regio- (78-94%) and enantioselectivities (80-97% ee) from 1-vinylcyclohexene, 4-methyl-1,3-pentadiene, and (E)-1-phenyl-1,3-butadiene. On the other hand, hydroformylation of 1,3-butadiene gave achiral product, (E)- and (Z)-S-pentenal, in up to 95% selectivity. (R)-(E)-2-Methyl-3-pentenal was formed as the major product from both (E)- and (Z)-1,3-pentadiene, but enantioselectivity of the reaction was low. Mechanistic aspects are also discussed. (C) 1997 Elsevier Science Ltd.