Synthesis
The general procedure for the synthesis of 6-chloro-4-methyl-3-pyridazinone from 3-methoxy-4-methyl-6-chloropyridazine was as follows: 6-chloro-3-methoxy-4-methylpyridazine (3.31 g, 20.9 mmol) was dissolved in a 4:1 solvent mixture of dioxane and water (100 mL), and 12.0 M aqueous hydrochloric acid (1.91 mL, 23.0 mmol ), and the reaction was stirred at 60°C for 60 hours. After completion of the reaction, the reaction mixture was concentrated in vacuum, and the crude product obtained was purified by silica gel column chromatography with an elution gradient of 1-30% of a solvent mixture of dichloromethane and methanol (containing 2% of ammonia as an additive) to finally obtain 6-chloro-4-methyl-3-pyridazinone (2.99 g, 99% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6) with chemical shifts of 13.03 (s, 1H), 7.44 (s, 1H), 2.05 (s, 3H).
References
[1] Patent: WO2017/70708, 2017, A1. Location in patent: Paragraph 00548; 00549; 00550; 00552
[2] Yakugaku Zasshi, 1962, vol. 82, p. 1005,1009
[3] Chem.Abstr., 1963, vol. 58, # 4559,
[4] Yakugaku Zasshi, 1962, vol. 82, p. 304,307
[5] Chem.Abstr., 1963, vol. 58, # 3427,
