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.