A mixture of 4-methoxy-4′-methylbiphenyl-3-yl-phosphonic acid dimethyl ester (300 mg, 1.1 mmol), N-bromosuccinimide (190 mg, 1.1 mmol) and a few crystal of benzoyl peroxide in CCl4 (15 mL) was refluxed and irradiated with a sun lamp for 1 h. More N-bromosuccinimde (30 mg, 0.17 mmol) was added and the mixture was refluxed for 30 min. After cooling to r.t., the mixture was diluted with CH2Cl2 and washed with H2O (3×), dried (MgSO4) and concentrated. The solid residue was swished with Et2O to give 280 mg (67%) of the title compound as a white solid.
