3) 1-(1-methyl-1H-pyrazol-4-yl)ethanol (20.2 g) was dissolved in dichloromethane (202 mL) and cooled to 0 °C under argon protection. Subsequently, activated manganese (IV) oxide (<5 μm, 209 g) was added to this solution. The reaction mixture was stirred at room temperature for 14 hours. Upon completion of the reaction, solid impurities were removed by filtration and the filtrate was concentrated under reduced pressure to afford 1-(1-methyl-1H-pyrazol-4-yl)ethanone as a solid product (18.1 g, 91% yield). The product was characterized by 1H-NMR (400 MHz, CDCl3): δ 2.42 (3H, s), 3.94 (3H, s), 7.86 (1H, s), 7.89 (1H, s).ESI-MS m/z: 125 ([M + H]+).
