On treatment with acids, is converted to a stabilized cation 3-methylene-3H-indolium, which can undergo further reaction to give diindol-3-ylmethane. Moody's group have demonstrated a formal [3+2] cycloaddition of the cation to a variety of alkenes to give cyclopenta[b]indoles: J. Chem. Soc., Perkin 1, 1127 (1995).