Anomalous Reaction of Arylmalononitriles with Nitric Acid. Para-Directing Nature of Dicyanomethyl Group and a Through-Ring Nitro/aci-Nitro Tautomerism of 4-Nitrophenylmalononitrile

Abstract

Abstract Phenylmalononitrile reacts with nitric acid in dichloromethane at room temperature to afford 1,2-bis(4-nitrophenyl)-1,1,2,2-tetracyanoethane as an initial product, which readily suffers oxidative cleavage to give 4-nitrobenzoyl cyanide. Contrary to common understanding, dicyanomethyl group exhibits no meta-directing property. 4-Nitrophenylmalononitrile is found to exist in two stable tautomeric forms, which undergo a facile nitro/aci-nitro interconversion across aromatic ring depending on the nature of solvent employed.