π-Extension of Strained Benzenoid Macrocycles Using the Scholl Reaction.

A series of bent p-terphenyl-containing macrocycles have been synthesized and then regioselectively brominated, arylated, and subsequently subjected to a Scholl-based cyclodehydrogenation reaction. Shortening the alkyloxy bridging unit of these macrocycles increases the bend in the p-terphenyl unit, as well as the strain energy (SE) of the central para-phenylene ring system. For the first time, incremental increases in SE of the macrocyclic structure of this class of benzenoid compounds have been investigated in the context of π-extension to strained polycyclic aromatic hydrocarbon systems using the Scholl reaction.