To a solution of 2,4,6-trimethyl-benzenesulfonic acid 3-bromo-2-isopropyl-8-nitro-4-oxo-4H-chromen-7-yl ester (1.906 g, 3.5 mmol) in dry toluene (18 ml) in a 20 ml capacity microwave tube is added p-methoxybenzylamine (0.69 ml, 5.26 mmol). The mixture is heated at 130° C. under microwave irradiation for 90 minutes and then at 140° C. under microwave irradiation for a further 30 minutes. Water (40 ml) is added, and the mixture is extracted with ethyl acetate (3×100 ml). The ethyl acetate extracts are combined, washed with saturated brine (50 ml), dried (MgSO4), filtered and evaporated. The crude product is purified by chromatography on silica gel using cyclohexane-ethyl acetate (8:1) as eluant. The product-containing fractions are evaporated under reduced pressure, and the residue is triturated with diethyl ether to give a pale yellow solid.
