Dibenzophosphole oxides were obtained from secondary hydrophosphine oxides with a biphenyl group by dehydrogenation via phosphine–hydrogen and carbon–hydrogen bond cleavage in the presence of a catalytic amount of palladium (II) acetate, Pd (OAc) 2. By using this reaction, a ladder-type dibenzophosphole oxide could also be synthesized by double intramolecular dehydrogenative cyclization.