Heterocyclic System : I. Reaction of 4-Oxo-4H-[I]-benzo- pyran-3-carboxaidehydes with Phenylhydrazine and Formation of 1-Phenyl-4-(2-hydroxybenzoyl)pyrazoles

Organic Chemistry Laboratory, Department of Biochemistry, Calcutta University, Calcutta 700019

Manuscript received 27 October 1976, revised 20 April 1977. accepted 6 August 1977

Phenylhydrazine undergoes 1 : 2 addition to the aldehydic function of 4-oxo-4H-[1] ­benzopyran-3-carboxaldehydes (I), the addition products on elimination of water giving the hydrazones (II). The latter on being refluxed in ethanolic potassium hydroxide yield 1-phenyl-4-(2-hydroxybenzoyl) pyrazoles (III)). The mechanism of this transformation and the mass spectral fragmentation of the pyrazoles (III) have been discussed.