Cyclocondensation of 6‐acetyl‐4,7‐dihydro‐5‐methyl‐7‐phenyl[1,2,4]triazolo[1,5‐ a ]pyrimidine with hydroxylamine and hydrazine

The cyclocondensation of 6‐acetyl‐4,7‐dihydro‐5‐methyl‐7‐phenyl[1,2,4]triazolo[1,5‐ a ]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a‐tetrahydro‐3,9a‐dimethyl‐4‐phenylisoxazolo‐[5,4‐ d ][1,2,4]triazolo[1,5‐ a ]pyrimidine ( 4a ) and 3a,4,9,9a‐tetrahydro‐3,9a‐dimethyl‐4‐phenyl‐1 H ‐pyrazolo[3,4‐ d ][1,2,4]triazolo[1,5‐ a ]pyrimidine ( 4b ), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5‐amino‐1,2,4‐triazol‐1‐yl)(3,5‐dimethylpyrazol‐4‐yl)phenylmethane ( 5 ). The structure determination of the compounds obtained is based on 1 H and 13 C nmr spectra including NOE measurements.