The synthesis of lin ‐benzoreumycin, lin ‐benzo‐1‐methylxanthine, and lin ‐benzo‐1,9‐dimethylxanthine

Commencing with 7‐chloro‐3‐methylquinazoline‐2,4(1 H ,3 H )‐dione ( 9a ), a five step synthesis of 7‐methylpyrimido[5,4‐ g ]‐1,2,4‐benzotriazine‐6,8(7 H ,9 H )‐dione ( lin ‐benzoreumycin, 6 ) has been accomplished. A synthesis of 1,7‐dimethylpyrimido[5,4‐ g ]‐1,2,4‐benzotriazine‐6,8(1 H ,7 H )‐dione ( lin ‐benzotoxoflavin, 5 ) employing an intermediate from the preparation of 6 ( i.e. , 7‐chloro‐3‐methyl‐6‐nitroquinazoline‐2,4(1 H ,3 H )‐dione, 9b ) was attempted but could not be accomplished beyond the dihydro precursor of 5 ( i.e. , 12 ). Compound 9b did lead to successful preparations of 7‐methylimidazo[4,5‐ g ]quinazoline‐6,8(5 H ,7 H )‐dione ( lin ‐benzo‐1‐methylxanthine, 7 ) and 3,7‐dimethylimidazo[4,5‐ g ]quinazoline‐6,8(5 H ,7 H )‐dione ( lin ‐benzo‐1,9‐dimethylxanthine, 8 ) by first reacting 9b with ammonia (for 7) or methylamine (for 8 ) followed by reductive cyclization in formic acid.