Catalytic Enantioselective Formation of C-C Bonds by Addition to Imines and Hydrazones: A Ten-Year Update

Catalytic enantioselective addition reactions offer an attractive solution, because they, in principle, permit the generation of large amounts of asymmetric material for the investment of a small quantity of the chiral source. Shibasaki and co-workers reported Direct Mannich-type reaction (DMTR) that involved the functionalization of propiophenone with formaldehyde and pyrrolidine in a three-component reaction catalyzed by (R)-LaLi 3tris(binaphthoxide) complex. The authors described the used of (R)-LLB and (R)-AlLibis(naphthoxide) [(R)-ALB], to promote the closely related direct Mannich-type reaction between isolated hemiaminal ethers and propiophenone. Shibasaki et al. reported a catalyst system formed from diethyl zinc and (S,S)-linked BINOL ligand 8a for the direct addition of R-hydroxy aromatic ketones to N-diphenylphosphinoyl imines. The addition reactions of CdN systems, particularly imine and hydrazones, remains a field of very great importance in organic synthesis.