Heteroaromatic belts through fold-in synthesis: mechanistic insights into a macrocycle-templated Friedel-Crafts alkylation

Abstract

Direct alkylation of 9,9',9''-triethyl[2.2.2](2,7)carbazolophane with dimethoxymethane or paraformaldehyde affords a belt-like heteroaromatic structure, which forms as a kinetic product in acid-catalyzed condensations. In a competing, thermodynamically favored process, polymeric structures are formed by a largely regioselective condensation of stereochemically rigid "semi-belts". The relationship between these reactivity routes is rationalized in terms of strain release and differential reversibility of consecutive condensation steps.

Keywords: cyclophanes; electrophilic substitution; fused ring systems; nitrogen heterocycles; polymers.