methyl 3-methoxy-1-methyl-1H-pyrazole-5-carboxylate

Synthesis

The general procedure for the synthesis of methyl 3-methoxy-1-methyl-1H-pyrazole-5-carboxylate from methyl 2-methyl-5-oxo-2,5-dihydro-1H-pyrazole-3-carboxylate and iodomethane is as follows: referring to Example 57, methyl 3-hydroxy-1-methyl-1H-pyrazole-5-carboxylate (2.34 g, 15.0 mmol), iodomethane (3.19 g 22.5 mmol), potassium carbonate (4.15 g, 30.0 mmol) and N,N-dimethylformamide (15 mL) were mixed and the reaction was stirred at room temperature for 18 hours. After completion of the reaction, the mixture was diluted with water (50 mL) and extracted with ethyl acetate (50 mL × 3). The organic layers were combined, washed with water (10 mL × 2) and subsequently concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent ratio: hexane/ethyl acetate = 100/0 → 50/50) to afford methyl 3-methoxy-1-methyl-1H-pyrazole-5-carboxylate (2.01 g, 79% yield) as a white solid. The product was characterized by 1H-NMR (DMSO-d6, 300 MHz): δ 3.78 (3H, s), 3.81 (3H, s), 3.94 (3H, s), 6.27 (1H, s).

References

[1] Patent: US2009/137595, 2009, A1
[2] Patent: EP2530078, 2012, A1. Location in patent: Page/Page column 209