The synthesis of<i>lin</i>-benzoreumycin,<i>lin</i>-benzo-1-methylxanthine, and<i>lin</i>-benzo-1,9-dimethylxanthine
作者:Stewart W. Schneller、Augusto C. Ibay、William J. Christ
DOI:10.1002/jhet.5570210331
日期:1984.5
AbstractCommencing with 7‐chloro‐3‐methylquinazoline‐2,4(1H,3H)‐dione (9a), a five step synthesis of 7‐methylpyrimido[5,4‐g]‐1,2,4‐benzotriazine‐6,8(7H,9H)‐dione (lin‐benzoreumycin, 6) has been accomplished. A synthesis of 1,7‐dimethylpyrimido[5,4‐g]‐1,2,4‐benzotriazine‐6,8(1H,7H)‐dione (lin‐benzotoxoflavin, 5) employing an intermediate from the preparation of 6 (i.e., 7‐chloro‐3‐methyl‐6‐nitroquinazoline‐2,4(1H,3H)‐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(5H,7H)‐dione (lin‐benzo‐1‐methylxanthine, 7) and 3,7‐dimethylimidazo[4,5‐g]quinazoline‐6,8(5H,7H)‐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.