A mixture containing 20 g of 1-(4-pyridinyl)-2-propanone and 30 ml ofhexamethylphosphoramide was diluted with 65 ml of dimethylformamidedimethyl acetal and the resulting mixture was refluxed for 30 min. TLCanalysis showed a single spot, thereby indicating completion of the reaction(in another run, the reaction appeared to be complete after 30 min at roomtemperature). The mixture was evaporated under reduced pressure and apressure, thereby resulting in a crystalline residue weighing 24 g. The residuewas purified by continuous chromatographic extraction on alumina (about 150g) using refluxing chloroform as eluant. After 90 min, the extract was heatedin vacuo to remove the chloroform, thereby leaving, as a light yellowcrystalline material, 23.2 g of 1-(4-pyridinyl)-2-(dimethylamino)ethenylmethyl ketone, alternatively named 4-dimethylamino-2-(4-pyridinyl)-3-buten-2-one.
To a mixture containing 23 g of 1-(4-pyridinyl)-2-(dimethylamino)ethenylmethyl ketone and 11 g of α-cyanoacetamide dissolved in 400 ml ofdimethylformamide was added with stirring 14 g of sodium methoxide and theresulting reaction mixture was heated in an oil bath under gentle reflux forone hour. TLC analysis showed no starting material in the reaction mixturewhich was then concentrated in vacuo on a rotary evaporator to a volume ofabout 80 ml. The concentrate was treated with about 160 ml of acetonitrileand the resulting mixture was stirred on a rotary evaporator with warminguntil homogenous and then cooled. The crystalline product was collected,rinsed successively with acetonitrile and ether, and dried overnight at 55°C toyield 28 g of crystalline product, namely, sodium salt of 1,2-dihydro-6-methyl-2-oxo-5-(4-pyridinyl)nicotinonitrile, the presence of cyano being confirmed byIR analysis. An 8 g portion of said sodium salt was dissolved in 75 ml of hotwater, the aqueous solution treated with decolorizing charcoal, filtered, thefiltrate again treated with decolorizing charcoal and filtered, and the filtrateacidified with 6 N hydrochloric acid by dropwise addition to a pH of 3. Theacidic mixture was diluted with ethanol and cooled. The crystalline productwas collected, dried, recrystallized from dimethylformamide-water and dried toproduce 3.75 g of 1,2-dihydro-6-methyl-2-oxo-5-(4-pyridinyl)nicotinonitrile,m.p. >300°C.
Another method of preparation of 1,2-dihydro-6-methyl-2-oxo-5-(4-pyridinyl)nicotinonitrile (Patent US 4,413,127)
A 69.5 g portion of 1-ethoxy-2-(4-pyridinyl)ethenyl methyl ketone wasdissolved in 300 ml of ethanol and to the solution was added 13.2 g ofmalononitrile. The resulting mixture was refluxed for 5 hours, crystals startingto separate after about 30 min of refluxing. The reaction mixture was allowedto cool to room temperature and, the precipitate of fine needles was filtered,washed with ethanol and dried in a vacuum at 90°C to yield 25.4 g of 1,2-dihydro-6-methyl-2-oxo-5-(4-pyridinyl)-nicotinonitrile, m.p. >300°C.Concentration of the mother liquor provided another 2.1 g of product, m.p.>300°C.
To a aqueous solution of 1,2-dihydro-6-methyl-2-oxo-5-(4-pyridinyl)nicotinonitrile was added one molar equivalent of lactic acid to prepare themonolactate of 1,2-dihydro-6-methyl-2-oxo-5-(4-pyridinyl)nicotinonitrile.
