Synthesis
Step A: A mixed solution of 2,5-hexanedione (6 mL, 51 mmol) and hydrazine monohydrate (2.5 mL, 51 mmol) in ethanol (50 mL) was heated to reflux for 3 hours. After completion of the reaction, the reaction mixture was concentrated under reduced pressure. The residue was mixed with 10% Pd/C catalyst (1.1 g) in anhydrous benzene (200 mL) and heated to reflux overnight. After the reaction mixture was cooled to room temperature, it was filtered through a diatomaceous earth pad to remove the catalyst. The filtrate was concentrated and purified by silica gel column chromatography (eluent: dichloromethane solution containing 6% methanol) to afford 3,6-dimethylpyrazine (3.1 g, 56% yield) as a light brown oil.1H NMR (500 MHz, CDCl3): δ 7.23 (2H, s), 2.69 (6H, s).
References
[1] Patent: US9617268, 2017, B2. Location in patent: Page/Page column 395; 396
[2] Journal of the American Chemical Society, 1956, vol. 78, p. 1961,1964
[3] Journal of the American Chemical Society, 1938, vol. 60, p. 2456
[4] Journal of the Chemical Society - Dalton Transactions, 1996, # 10, p. 2117 - 2122
[5] Gazzetta Chimica Italiana, 1950, vol. 80, p. 783,786
