Dimethyl Sulfate → 4-(1-methyl-1H-pyrazol-3-yl)pyridine

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Reaction Steps

To 150 mL tetrahydrofuran was added 4-(1H-pyrazol-3-yl)pyridine (4.96 g; Example 3, Step 1) and the solution cooled in ice. To this was added slowly 1.64 g of a 60% suspension of sodium hydride in mineral oil. After gas evolution ceased, the mixture was stirred at ambient temperature for 30 min, cooled back down in ice, and 3.4 mL dimethylsulfate was added. The mixture was allowed to slowly warm to ambient temperature. After 1 hour the reaction mixture was evaporated and the dark brown residue partitioned between saturated aqueous sodium bicarbonate and ethyl acetate. The ethyl acetate was washed with saturated aqueous sodium bicarbonate, brine, dried over magnesium sulfate, filtered, and evaporated under vacuum to afford 4.6 g crude product as a pale yellow solid. The crude material was taken up in a diethyl ether and hexane mixture, filtered through celite, and allowed to crystallize. A total of 2.98 g (55% yield) pale yellow crystals were obtained. 1H NMR (CDCl3) was consistent with a single isomer of the desired structure. LC/MS showed one peak with a M+1 molecular ion of m/z 160.5 by positive ESI.

Provenance & Evidence