Incorporation of an indole-containing diarylbutylamine pharmacophore into furo[2,3-a]carbazole ring systems

Due to concurrent oxidation of the indole moiety in the starting carbazole alkenol, an epoxidation route aiming at incorporation of a conformationally constrained diarylbutylamine failed to give the desired furo2,3-a]carbazole ring system. Instead, an indole epoxide intermediate was generated, which underwent rearrangement involving participation of a vicinal OH group. The required furo2,3-a]carbazole could, however, be accessed via a Hg²⁺-induced cyclisation of a carbazole alkynol.