A mixture of 2-methylnicotinamide (13 g, 95.6 mmol, 1 eq.) and N,N-dimethylformamide dimethyl acetal (18.2 mL) was heated at 50 °C for 2 hours. During the second hour of the reaction, all volatiles were removed by distillation under reduced pressure. After cooling the residue to room temperature, it was diluted with 100 mL of anhydrous N,N-dimethylformamide, and then sodium hydride (5 g, 124.3 mmol, 1.3 equiv, 60% oil dispersion; note: vigorous release of hydrogen) was added in batches. The reaction mixture was heated at 80 °C for 2.5 h. Subsequently, the mixture was cooled in an ice bath, 25 mL of 2-propanol was added slowly and allowed to stand at 0-5 °C overnight. The resulting solid was collected and dissolved in 10 mL of hot water. The resulting solution was filtered, the filtrate was cooled in an ice bath, and the pH was adjusted dropwise to 7.0 by adding concentrated hydrochloric acid. after storage at 0-5 °C for 3 h, the precipitated solid was collected, washed with ice-cold water, and dried under vacuum to afford 1,6-naphthalenopyridin-5(6H)-one (3 g, 32% yield).1H NMR (DMSO-d6, 300 MHz): δ 8.90 (s, 1H), δ 8.49 (d, J = 7.6Hz, 1H), 7.51-7.43 (m, 2H), 6.61 (d, J = 7.6Hz, 1H).
