15986-92-2

107-15-3

431-03-8

15986-92-2

Over a period of 2 hours, 2,3-butanedione (18.6 g, 216 mmol, dissolved in 200 mL of anhydrous ether) was added slowly and dropwise to a solution of ethylenediamine (13 g, 216 mmol) in anhydrous ether (600 mL). The reaction mixture was stirred continuously for 3 hours at room temperature. Subsequently, the clarified reaction solution was concentrated under reduced pressure to give a brown oily crude product. Purification of the crude product by reduced pressure distillation resulted in 16.6 g (70% yield) of the target compound 5,6-dimethyl-2,3-dihydropyrazine (Formula F) as a clarified yellow oil. The boiling point was 60 °C/16 mm Hg. Nuclear magnetic resonance hydrogen spectroscopy (NMR, CD3) data were as follows: δ 3.3 (broad single peak, 4H), 2.1 (single peak, 6H) ppm.