Ethyl 2-cyanoacetate, reaction with hydrazone

A completely different approach initially involves the addition of the carbanion of ethyl 2-cyanoacetate 142 in the presence of base to the imine group of 2-naphthylsulfonyl hydrazone 147 followed by cyclization and oxidation to pyrazol-3-one 150 (02NN469) (Scheme 34). The reaction requires heating in ethanol with triethylamine and it is suggested that intermediate 148 is first produced, and then undergoes an intramolecular acyl substitution resulting in the unstable pyrazol-3-one 149. The latter is prone to oxidation by molecular oxygen and is converted to stable pyrazol-3-one 150. 

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