Different 3-[2-(3,4-dihydro-1-naphthyl)ethyl]imidazolidine-2,4-diones and 3-[2-(1-naphthyl)ethyl]imidazolidine-2,4-diones, when heated in polyphosphoric acid at 150 °C, underwent chemoselective intramolecular cyclization to afford the 13,16-diazaestrone steroids and 13,16- diazaequilenin steroids respectively.
polyphosphoric acid; chemoselective cyclization; 13,16-diazaestrone steroids; 13,16- diazaequilenin steroids
