Nickel(II)-catalyzed Michael additions. Formation of quaternary centers and diastereoselective addition of enantiopure N -acetoacetyl-4-benzyloxazolidin-2-one
Ni(acac)2 and Ni(salicylaldehydate)2 are effective catalysts for conjugate additions of 2-methyl-1,3-dicarbonyl compounds to Michael acceptors. Significant diastereomeric excesses are obtained in the Michael additions of enantiopure N-acetoacetyl-4-benzyloxazolidinones. Reaction of the latter compound with aryl isocyanates affords unsymmetrical diamides of malonic acid.
The nickel(II) complex of the Schiff base of salicylaldehyde and 4-perfluorodecylaniline catalyzes the conjugate addition of beta-diketones to electron-deficient substrates. Electrophilic amination with azodicarboxylate affords quaternary centers. The catalyst is recovered in solution and reutilized. Isolation of reaction products is very simple and does not require chromatography. (C) 2000 Elsevier Science Ltd. All rights reserved.