Iminophosphorane-mediated synthesis of fused [1,2,4]triazines: preparation of [1,2,4]triazolo[5,1-c][1,2,4]triazine and [1,2,4]triazino[4,3-b][1,2,4,5]tetrazine derivatives

Abstract

A number of [1,2,4]triazolo[5,1-c][1,2,4]triazine and [1,2,4]triazino[4,3-b][1,2,4,5]tetrazine derivatives have been prepared. 3-(2-Benzylidene-1-methylhydrazino)-6-methyl-5-oxo-4-triphenylphosphoranylideneamino-4,5-dihydro-1,2,4-triazine (3), available from the Iminophosphorane (2) and benzaldehyde, reacts with aliphatic isocyanates at room temperature to give the corresponding 8H[1,2,4]triazolo[5,1-c][1,2,4]triazinones (6)–(12). On the other hand, Iminophosphorane (2) reacts with acyl chlorides at room temperature to give 3-(2-acyl-1-methylhydrazino)-6-methyl-5-oxo-4-triphenylphosphoranylideneamino-4,5-dihydro-1,2,4-triazines (13)–(15), which react with isocyanates at room temperature to give 2H-[1,2,4]triazino[4,3-b][1,2,4,5]tetrazines (17)–(24).