A mixture of 2.41 g (16.98 mmol) phosphorus pentoxide, 2.32 g (16.85 mmol) triethylamine hydrochloride, 3 g (17.73 mmol) 4-aminobiphenyl, and 1 g (4.21 mmol) 4-(4-pyridylmethyl)-1(2H)-phthalazinone is stirred for 20 h at 200° C. under a nitrogen atmosphere. After cooling to RT, the hyalinocrystalline melt is distributed between a dichloromethane/methanol mixture (99:1) and a mixture of water and saturated aqueous carbonate solution on (1:1) with intensive stirring and the use of an ultrasonic bath. The organic phase dried over sodium sulfate is evaporated under vacuum and the residue purified by means of flash chromatography on silica gel with particle size 0.04-0.06 mm, using a dichloromethane/methanol mixture (49:1). Title compound is obtained after evaporation of the product-containing fractions under vacuum and recrystallization of the residue from acetonitrile; m.p. 189-191 °C.; ESI-MS: (M+H)+=389.
