Dichloromethane → Thieno[3,4-b]pyrazine

Participants

Reaction Steps

3,4-diaminothiophene dihydrochloride (12, 1.03 g, 5.52 mmol) was added into 5% aqueous Na2CO3(60 mL). An glyoxal aqueous solution (0.36 g, 6.1 mmol) prepared by diluting 40% glyoxal solution (0.885 g) with water (15 mL) was added to the reactant for 5 minutes. The reaction mixture was stirred at room temperature for at least 3 hours, and extracted with ether and/or ethylacetate several times. A collected organic layer was washed with water and dried with anhydrous sodium sulfate, followed by concentration in a rotary evaporator, thereby obtaining a light brown oil. An assay sample was prepared by dissolving the oil into a small amount of CH2Cl2 and purified with column chromatography using hexane as an eluent, thereby obtaining 13 (0.57 g, 76%) as a light brown oil. 1H NMR (CDCl3, 400 MHz, d/ppm): 8.51 (s, 2H, N═CHCH═N), 8.03 (s, 2H, 2×CH—S). 13C NMR (CDCl3, 100 MHz, d/ppm): 144.41, 142.80, 118.00. C6H4N2S (136.17): Theoretical value C, 52.92; H, 2.96; N, 20.57; S, 23.55; Experimental value C, 53.07; H, 3.11; N, 20.50; S, 23.63.

Provenance & Evidence