Reaction of 1-chloromethylisatin with indole

Abstract

In the condensation of N-chloromethylisatin with indole and 2-methylindole in the presence of triethylamine, instead of the expected N-skatylisatins the products of their subsequent transformations with opening of the five-membered ring of isatin -o-(N-skatylamino)- and o[N-(2-methylskatyl)amino]benzoylcaproic acids —were isolated. In addition to the formation of these α-keto acids, under the indicated conditions one observes dimerization of N-chloromethylisatin and N-chloromethyl-5-methylisatin to give 2-(1-isatinylmethyloxy-3H-indolin-3-one and 2-(5-methyl-1-isatinylmethyloxy)-5-methyl-3H-indolin-3-one, respectively, i.e., dimers containing isatin rings in lactam and lactim forms. The structures of the compounds were confirmed by IR, PMR, and mass-spectral data.