SYNTHESIS OF DIMETHYLPYRAZOLO[1,2-A]BENZOTRIAZOLES AND OF METHYLPYRAZOLO[1,2-A]QUINOXALINES BY CYCLIZATION OF 3,5-DIMETHYL-1-(2-NITRENOPHENYL)PYRAZOLES

The thermal and photochemical decomposition of a series of 5-substitut ed 1-(2-azidophenyl)-3,5-dimethylpyrazoles has been examined under a h omogeneous set of conditions. Cyclization to pyrazolo[1,2-a]benzotriaz ole (via singlet nitrene) is an efficient process except when the phen yl substituent induces intersystem crossing to the azide triplet or co mpensates for its electrophilicity. On the contrary, cyclization to py razolo[1,2-a]quinoxaline (via triplet nitrene) is not a preparatively useful process, due to competition with dimerization to the azo deriva tives and reduction to aminophenylpyrazoles.