Abstract: A process for the preparation of substituted benzothiazinoindoles of general formula (I) wherein R1, R2, and R4 are independently selected from hydrogen, chloro, fluoro, amino, nitro, cyano, CHO, (C1-C3)alkyl, perhalo(C1-C3)alkyl, (C1-C3)alkoxy, aryl, aralkyl, aralkoxy, (C5-C7)heterocyclyl, (C5-C7)heterocyclylalkyl, (C5-C7)heterocyclyloxy, acyl, acetyl, alkylamino, aminoalkyl, amide, hydroxyalkyl, carboxylic acid and its derivatives. The process comprises cyclization of compound of general formula-II (i.e. substituted 1-benzenesulfonyl-7-bromo-1H-indole), formula (II) wherein R1, R2, R3 and R4 are attached using suitable catalyst and solvents.