STUDIES WITH ALKYLHETEROCYCLIC CARBONITRILES: A NOVEL SYNTHETIC ROUTE TO SEVERAL NEW ANNELATED PYRAZOLO[5,1-C]-1,2,4-TRIAZINE DERIVATIVES

Abstract

3-Phenylpyrazol-5-yl diazonium chloride (1a) was coupled with 2-aminocrotonitrile (4) to afford 4-phenyl-6-methylpyrazolo[5,1-c]-1,2,4-triazine-7-carbonitrile (5). Upon reaction with sulfur, compound 5 was transformed into 8-amino-4-phenylthieno[4,3-e]pyrazolo[5′,1-c']-1,2,4-triazine. Compound 6 underwent 4 + 2 cycloaddition with several dipolarophiles such as maleic anhydride, N-phenylmaleimide and acrylonitrile to afford a variety of new annelated pyrazolo[5,1-c]-1,2,4-triazine derivatives via hydrogen sulfide elimination. The structures of the newly synthesized compounds were determined by elemental analyses and spectral data. A sequence leading to the formation of these compounds and their reactions is described.

Key Words:

• 4 + 2 Cycloaddition
• thieno[4,3-e]pyrazolo-triazines
• annelated pyrolotriazines