Michael addition of malononitrile to indenones: Synthesis and characterization of 2-(1-oxo-2,3-dihydro-1H-inden-2-yl)(aryl)(methyl)malononitrile derivatives

Indanones 3 were prepared from the reaction of indanone (1) with corresponding benzaldehyde derivatives 2, as described in the literature. Then, indenones 3 were subjected to KOtBu-catalyzed Michael addition with malononitrile to give a mixture of diastereomers 5 with a low conversion and no diastereoselection. Utilization of phase-transfer catalyst such as benzyltriethylammonium chloride or N-benzylcinchonidinium chloride had a positive effect on both conversion and diastereoselection. The structure of diastereomers 5 was determined by spectroscopic methods (NMR, IR).