Inhibitors of platelet aggregation. 4. [1,2,5]Thiadiazolo[3,4‐ c ]acridines, 7,8,9,10‐Tetrahydro[1,2,5] thiadiazolo[3,4‐ c ]acridities, and 8,9‐Dihydro‐7 H ‐cyclopenta[ b ][1,2,5] thiadiazolo[3,4‐ H ]quinolines

The condensation of 4‐amino‐2,1,3‐benzothiadiazole (IV) with diphenyliodonium‐2‐earboxylate gave N ‐(2,1,3‐benzothiadiazoI‐4‐yl)anthranilic acid (V) (28%), which was cyclized with phosphorus oxychloride to 6‐chloro[1,2,5]thiadiazolo[3,4‐ c ]acridine (VI) (84%). Treatment of VI with 3‐(dimethylamino)‐1‐propanethiol hydrochloride in phenol afforded 6‐[ [3‐(dimethylamino)‐propyl]thio] [1,2,5]thiadiazolo[3,4‐ c ]acridine (VII) (65%). The reaction of IV with a mixture of methyl and ethyl 2‐oxocyclohexanecarboxylate gave the adduct, which was ring closed in Dowtherm to 7,9,10,1 1‐tetrahydro[1,2,5] thiadiazolo[3,4‐ c ]acridin‐6(8 H )one (VIII) (70%). Chlorination of VIII with phosphorus oxychloride gave 6‐chloro‐7,8,9,10‐tetrahydro[1,2,5]thiadiazolo[3,4‐ c ]acridine (IX) (84%), which was condensed with 3‐(dimethylamino)‐1‐propanethiol hydrochloride in phenol yielding 6‐[ [3‐(dimethylamino)propyl]thio]‐7,8,9,10‐tetrahydrof 1,2,5]‐thiadiazolo[3,4‐ c ]acridine (X) (27%). 6‐[ [3(1)imethylamino)propyl]thio]‐8,9‐dihydro‐7 H ‐cyclopenta[ b ] [1,2,5]thiadiazolo[3,4‐ h ]quinoline (XIII) (25%) was prepared similarly from IV and a mixture of methyl and ethyl 2‐oxocyclopentanecarboxylate via 7,8,9,10‐tetrahydro‐6 H ‐cyclopenta[ b ][1,2,5]thiadiazolo[3,4‐ h ]quinolin‐6‐one (XI) (85%) and 6‐chloro‐8,9‐dihydro‐7 H ‐cyclopenta[ b ][1,2,5]thiadiazolof3,4‐ h ]quinoline (XII) (56%). The effects of compounds VII‐XIII as inhibitors of platelet aggregation are discussed.