Synthesis and Ring Opening of Alkaloid-Type Compounds with a Novel Indolo[2,3-c][2]benzazepine Skeleton

Alkylation of the magnesium salts of 2,3-disubstituted indoles with 2-bromomethylbenzonitrile gave 3-(2-cyanobenzyl)-3H-indole derivatives. Reduction of the cyano group of N-methyl 3-(2-cyanobenzyl)-3H-indolium salts afforded previously unreported indolo[2,3-c][2]benzazepines, while acid hydrolysis gave the corresponding indolo[2,3-c][2]benzazepinones. The action of strong protonic acids on indolo[2,3-c][2]benzazepines causes opening of the benzazepine ring annelated to the indole system to form 3H-indolium S salts.