Ethanol → 3-(2-Cyanophenyl)-5-(2-pyridyl)-1-phenyl-1,2-dihydropyridin-2-one sulfate

A mixture of 3-(2-cyanophenyl)-5-(2-pyridyl)-1-phenyl-1,2-dihydropyridin-2-one (1.0 g, 0.687 mmol) and ethanol (small amount) was concentrated under reduced pressure, followed by adding ethyl acetate (small amount) to the residue before further concentration under reduced pressure. A 10% (v/v) H2SO4/ethyl acetate solution (0.439 mL, 0.824 mmol) was added to an ethyl acetate (15 mL) suspension containing the resultant residue, which was then stirred at room temperature for 4 days. The precipitated solid was collected by filtration, washed with ethyl acetate (small amount), and then dried under reduced pressure to provide 475 mg of the title compound as white crystals.