A New Synthesis of Ylidenemalononitriles

Abstract

Ylidenemalononitriles are useful reagents, reactive as Michael acceptors², and in the synthesis of indenones and indanones³, aminonaphthalenes⁴, and lactones⁵. Syntheses of these reagents usually involves a typical Knoevenagel reaction between a carbonyl compound and malononitrile, catalyzed by base⁶. Yields in this condensation vary widely, and are especially poor with hindered ketones and diaryl ketones. For example, Schenck and Finken⁷ allowed equivalent amounts of benzophenone and malononitrile to react in alcohol for four days, with ammonia as catalyst, and obtained a 13% yield of the corresponding ylidenemalononitrile. Later this was increased by removing water from a refluxing benzene solution of the reactants for 48 hrs³. Although a 68% yield was reported, it was based on unrecovered ketone, and the actual yield was less than 40%. Charles⁸ has reported the synthesis of the same substance by condensing the