Synthesis of pyrazolo[4,3‐ d ]oxazoles

Abstract 1‐Phenyl‐3‐methyl‐5‐pyrazolone‐4‐oxime reacted with benzylamine, methylamine, methyl‐ and ethyl ioides to give 3‐methyl‐1,5‐diphenyl‐1 H ‐, 3‐methyl‐1‐phenyl‐1 H ‐ and 3,5‐dimethyl‐1‐phenyl‐1 H ‐pyrazolo[4,3‐ d ]oxazoles I, II. The structure of I was elucidated authentically through other routes by interaction of 1‐phenyl‐3‐methyl‐4,5‐dioxopyrazolone with benzylamine and/or benzaldehyde and ammonium acetate. Various 3‐meth‐yl‐5‐aryl‐1‐phenyl‐1 H ‐pyrazolo[4,3‐ d ]oxazoles IV were synthesized by the reaction of 4,5‐dioxopyrazolone with aromatic aldehydes in the presence of ammonium acetate. Also, the structure of I was elucidated authentically via other routes by the reaction of 1‐phenyl‐3‐methyl‐4‐imino‐5‐pyrazolone with each of benzylcyanide, benzylamine, benzaldehyde and benzalaniline.