A mixture of 300 mg (1.19 mmol) rac4-[1-(4-pyridyl)ethyl]-1(2H)-phthalazinone, 683 mg (4.77 mmol) phosphorus pentoxide, 657 mg (4.77 mmol) triethylamine hydrochloride, and 609 mg (4.77 mmol) 4-chloroaniline is heated for 8 h to 205° C. The brown solution is taken up in dichloromethane/methanol 19:1, washed successively with sat. Na2CO3 solution, 3× with water and brine, and the organic phase (Na2O4) is washed and concentrated by evaporation. Chromatography (SiO2; ethyl acetate/CH3OH, 19:1) yields the title compound: m.p.: 132-134° C.; Anal. calc.(C21H17N4Cl.½CH3OH) C, 68.52%; H, 5.08%; N, 14.87%; found C, 68.4%; H, 5.0%; N, 14.9%. The starting material is prepared as follows:
