Rate acceleration of triethylamine-mediated guanidine-catalyzed enantioselective Michael reaction

Abstract

A chiral bicyclic guanidine was found to be an excellent catalyst for enantioselective Michael reactions. It was observed that additives such as non-chiral amines could accelerate the rate of reaction. When triethylamine (Et3N) was as used as the solvent, the reaction rate can be increased up to 1000 times without compromising the enantioselectivity. Michael acceptors such as 2-cyclopenten-1-one 2 and N-alkylmaleimides were investigated, with various commercially available Michael donors such as dialkyl malonates and benzoylactetates. Michael adducts were obtained in excellent enantiomeric excesses (up to 96%) and yields (up to 99%). © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.