Bromination of 2, 3-dimethylindole

In bromination of indoles, the bromine atom will most probably enter at position 2 or 3. For example, indole and 2-methylindole 1] brominate at position 3, while some 3-substituted indoles 2] brominate at position 2. In the case of 2, 3-dimethylindole it was shown 3], that bromine does not enter the benzene ring, as would have been expected, but adds to the active 2, 3 (double) bond of the indole.