7‐(2‐fluorobenzyl)‐4‐(substituted)‐7‐H‐imidazo[4,5‐d −1,2,3‐triazines and −7H‐pyrazolo[3,4‐d]‐1,2,3‐triazines. Synthesis and anticonvulsant activity

The imidazo[4,5‐d]‐1,2,3‐triazine and pyrazolo[3,4‐d]‐1,2,3‐triazine analogues of the potent anticonvul‐sant purine, BW 78U79 (9‐(2‐fluorobenzyl)‐6‐methylamino‐9H‐purine, 1), were synthesized and tested for anticonvulsant activity. The imidazo[4,5‐d]‐1,2,3‐triazines 11–13 were prepared in four steps from 5‐aminoimidazole‐4‐carboxamide (2) and the pyrazolo[3,4‐d]‐1,2,3‐triazines 18–21 were synthesized starting with 5‐amino‐1‐(2‐fluorobenzyl)pyrazole‐4‐carbonitrile (14). The intermediate 1,2,3‐triazin‐4‐ones 6 and 16 were converted to the 4‐substituted targets via the 4‐(4‐dimethylaminopyridinium) salts 10 and 17. Imidazotriazine 11 had potent anticonvulsant activity against maximal electroshock‐induced seizures, but its propensity to cause emesis precluded further development.