The reactions of some indole derivatives with benzoyl nitrate. Novel oxidative coupling reactions of 2-methylindoles

Abstract

Indole derivatives with a free position 3 are converted by benzoyl nitrate into the corresponding 3-nitro-derivatives. Under the same conditions, 3-methylindole gives 3-methyl-2-nitroindole, and 2,3-diphenylindole yields a mixture containing 3,3-diphenyloxindole and 6-nitro-2,3-diphenylindole. 2,3-Dimethylindole is oxidized by benzoyl nitrate to 3-methylindole-2-carbaldehyde, and under somewhat different conditions to two compounds, which, on the basis of spectral and chemical evidence, are identified as 5a,10b,12-trimethyl-5a,6,10b,11-tetrahydropyrrolo[1,2-a:5,4-b′]di-indole and the corresponding 6-nitroso-derivative. 3-Ethyl- and 3-phenyl-2-methylindole give similar products.