Diethyl Oxalate → ethyl 1'H,2H-[3,3'-bipyrazole]-5-carboxylate

Participants

Reaction Conditions

Reaction Steps

Pieces of sodium (0.26 g) were slowly added to ethanol (12 ml) with stirring until all sodium had dissolved. 1-(1H-Pyrazol-5-yl)ethanone (8.61 mmol, 0.948 g) and diethyl oxalate (8.61 mmol, 1.258 g) was added. The mixture was heated to 75° C. for 3 h after which the stirring continued at RT overnight. Hydrazine hydrochloride (8.61 mmol, 0.590 g) dissolved in water (6 ml) was added. The resulting mixture was again heated to 75° C. for 3 h. The mixture was cooled to RT and neutralized by adding 2 M NaOH. The mixture was extracted twice with EtOAc and the combined organics were washed with water and brine. The organic phase was dried, filtered and evaporated. The crude product was purified by flash chromatography. 0.404 g of the title compound was obtained. 1H-NMR (400 MHz, MeOH-d4): δ 1.39 (t, 3H), 4.38 (q, 2H), 6.69 (d, 1H), 7.10 (bs, 1H), 7.70 (bs, 1H).

Provenance & Evidence