Bicyclic heterocycles with nitrogen at the ring junction 1. Synthesis and chemistry of imidazo[5,1-f]-1,2,4-triazines

The synthesis of the potential bronchodilators 2-amino-5-methyl-7-propylimidazo[5,1-f][1,2,4]triazin-4(3H)-one (12) and fhe corresponding triazine (2) is described and some chemical reactions of this novel ring system are discussed. Although X-ray analysis of the methanesulphonate salt of (12) indicated that protonation occurred on the nitrogen atom at position 6, acylation of the primary amino-group could still be achieved using a carboxylic acid in the presence of methanesulphonyl chloride.