A New Synthesis of Ylidenemalononitriles

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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