Synthesis of fluorenones via quaternary ammonium salt-promoted intramolecular dehydrogenative arylation of aldehydes

Biologically interesting fluorenone, xanthone and anthrone derivatives have been prepared via an intramolecular oxidative acylation process. This novel direct acylation reaction proceeded without the aid of any transition metals, acids or bases, and uses a catalytic amount of a quaternary ammonium salt in the presence of a persulfate oxidant. Initial mechanistic studies have been carried out to elucidate the reaction pathway.