Secondary–secondary diamine catalysts for the enantioselective Michael addition of cyclic ketones to nitroalkenes

Secondary–secondary diamines derived from S-proline are efficient catalysts for the ketone–nitroalkene Michael addition reaction. The stereoselectivity of the Michael addition is dependant on the pKa of the N-substituted aminomethyl pendant in these diamines. N′-Aryl aminomethyl pyrrolidines provide γ-nitroketones with moderate to good enantiomeric excess (65–92%). Removal of the hydrogen-bond donor group by N-methylation results in a dramatic reduction of enantioselectivity (average ee 6%).