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-7H-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-chloro1,2,5]thiadiazolo3,4-c]acridine (VI) (84%). Treatment of VI with 3-(dimethylamino)-1-propanethiol hydrochloride in phenol afforded 6- 3-(dimethylamino)-propyl]thio] 1,2,5]thiadiazolo3,4-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-tetrahydro1,2,5] thiadiazolo3,4-c]acridin-6(8H)one (VIII) (70%). Chlorination of VIII with phosphorus oxychloride gave 6-chloro-7,8,9,10-tetrahydro1,2,5]thiadiazolo3,4-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]-thiadiazolo3,4-c]acridine (X) (27%). 6- 3(1)imethylamino)propyl]thio]-8,9-dihydro-7H-cyclopentab] 1,2,5]thiadiazolo3,4-h]quinoline (XIII) (25%) was prepared similarly from IV and a mixture of methyl and ethyl 2-oxocyclopentanecarboxylate via 7,8,9,10-tetrahydro-6H-cyclopentab]1,2,5]thiadiazolo3,4-h]quinolin-6-one (XI) (85%) and 6-chloro-8,9-dihydro-7H-cyclopentab]1,2,5]thiadiazolof3,4-h]quinoline (XII) (56%). The effects of compounds VII-XIII as inhibitors of platelet aggregation are discussed.