Synthesis
Hydrazine hydrochloride (58 g, 552 mmol) is dissolved in hot water (300 mL) and dimethyl maleic anhydride (58 g, 460 mmol) is added in portions and the suspension stirred at reflux for 16 h. The suspension is cooled down to room temperature and the precipitate is filtered, washed with water and dried at 40° C. under vacuum to yield 4,5-dimethyl-1,2-dihydro-pyridazine-3,6-dione (36) (64 g, 99%).
References
[1] Patent: US2010/41663, 2010, A1. Location in patent: Page/Page column 41
[2] Journal of Organic Chemistry, 1955, vol. 20, p. 707,708
[3] Journal of the American Chemical Society, 1954, vol. 76, p. 4454,4457
[4] Patent: US2011/34451, 2011, A1. Location in patent: Page/Page column 57
[5] Patent: US2011/34452, 2011, A1. Location in patent: Page/Page column 36
