Reaction of 1-benzenesulfonylindole-2,3-dicarboxylic anhydride with wittigreagents: Synthesis of pyrrolo[1,2-a]-indoles and cyclopent[b]indole

Treatment of 1-benzenesulfonylindole-2,3-dicarboxylic anhydride with methyl enetriphenylphosphorane gave the corresponding ylide. After esterification of the carboxyl group and removal of the benzenesulfonyl group of the ylide , the obtained ylide was reacted with aldehydes to yield alpha,beta -unsatu rated ketones, which were converted to pyrrolo[1,2-a]indoles. We also exami ned the reactivity of the anhydride with (carbethoxymethylene)triphenylphos phorane and (carbethoxyethylidene)triphenylphosphorane.