In a 2000 L reaction flask, 160 g of 1,3-dibenzyluracil, 55.2 g of cyanoacetamide (1.2 eq.) and sodium methanol were added. Subsequently 2556.6 g (2.5 eq.) of liquid and 800 mL of methanol were added and stirring was initiated. The temperature of the reaction system was raised to 45-50 °C and the reaction was maintained at this temperature for 6 hours. The progress of the reaction was monitored by TLC and after confirming the completion of the reaction, the reaction solution was cooled to 20-30 °C, filtered and the filter cake was washed with 100 mL of methanol. The filter cake was transferred to a 2000 L reaction flask along with 800 g of water. After heating to 70-75 °C, the reaction solution was slowly cooled to 0-5 °C and kept at this temperature for 2 h. Subsequently, filtration was performed and the filter cake was washed with an appropriate amount of ice water to obtain 2,6-dihydroxynicotinonitrile monosodium salt dihydrate. The temperature was controlled at 20-30 °C and the filter cake was slowly added to an aqueous hydrochloric acid solution (prepared from 480 g of water and 66.6 g of concentrated hydrochloric acid). The crystallization was held at 20-30 °C for 1 h. The crystallization was continued to be cooled to 0-5 °C and kept for 2 h. The filtration was withdrawn and the filter cake was washed with an appropriate amount of ice water. After drying, 74.5 g of white solid 3-cyano-2,6-dihydroxypyridine was obtained in 86.5% yield. Its 1H NMR spectrum is shown in Figure 6.
