Abstract 2-Carboxy-1-alkylindole-3-acetic acid anhydrides (I) condensed with S- methylisothiosemicarbazide in DMF to form 5, 11-dihydro-6-methyl-2-methylthioindolo [3′, 2′: 4, 5] pyrido [1, 2-b]-s-triazol-5-one (II). Compound II underwent ring opening on refluxing with sodium hydroxide solution to give IV. The anhydride I reacted with primary amines in benzene to give 2-carboxy-1-alkylindole-3-acetanilide derivatives (VI) which ...