In the presence of Bronsted and Lewis acids, 1-vinyl-4,5,6,7-tetrahydr
oindole is transformed into its dimer, 1-vinyl-2-[1-(4,5,6,7-tetrahydr
oindolyl)ethyl] -4, 5,6,7-tetrahydroindole, and polymers containing un
its of the dimer and segments of oxidized tetrahydroindole cycles.