Tunable reactivity of triphosgene-triethylamine: A study on the synthesis of pyrrole-based tricyclics

Abstract The synthesis of novel pyrrolo[1,2-c][1,3]benzodiazepine and pyrrolo[3,2-c]- [1]benzazepine ring systems from (2-aminophenyl)(1H-pyrrol-2-yl)methanone and 2-[(1H-pyrrol-2-yl)methyl]aniline is presented, utilizing triphosgene as carbonylation-cyclization reagent for the formation of the 7-membered heterocycle. A study of the reaction shows that small changes in the reaction conditions affect dramatically the course of the reaction. Acidity as well as aqueous workup play significant roles in the reaction outcome, directing product formation and revealing important aspects of triphosgene mediated cyclizations.