Regioselectivity in the Controversial Scholl Reaction of 1‑Benzoylpyrene: Formation of a Five-Member Ring Is Not Unexpected

Intramolecular Scholl reaction of 1-benzoylpyrene (1) gave 8H-dibenzo­[def,qr]­chrysen-8-one (2) and 11H-indeno­[2,1-a]­pyren-11-one (3) in a 1:2 ratio. The structures of 2 and 3 were determined, using 1H NMR, 13C NMR, and IR spectroscopies. A DFT B3LYP/6-311G­(d,p) study of the reaction’s arenium–cation mechanism of (E)-1 and (Z)-1 giving 2 and 3, respectively, indicated the reaction’s regioselectivity and kinetic control. The analogous reaction of 1-(1′-naphthoyl)­pyrene gave exclusively 13H-benz­[4,5]­indeno­[2,1-a]­pyren-13-one. Contrary to previous claims, the preferred formation of five-member rings in Scholl reactions is not unexpected.