Organocatalyzed Highly Enantioselective Michael Additions of Malonates to Enones by Using Novel Primary-Secondary Diamine Catalysts

A novel primary-secondary diamine catalyst readily available from primary amino acids in three steps for the highly enantioselective Michael additions of malonates to α,β-unsaturated ketones was reported. The Michael reaction of dimethyl malonate with benzylideneacetone was selected as a model reaction for catalyst evaluation. The length of the alkyl chain is found to influence the catalytic abilities of the catalysts and the n-propylated catalyst gave the highest yield and ee value. The addition of a series of malonates to enone performed under the optimized conditions is found to be sensitive to the steric hinderance on the malonates. Heterocyclic furan enone is found to perform well to give the desired product in 92% yield and 99% ee, while no decrease in yield and ee value is observed for sterically hindered enone.