Sodium hydride → Methyl 1-cyclobutyl-1H-indazole-3-carboxylate

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To a suspension of sodium hydride (60% in mineral, 817 mg, 20.4 mmol) in N,N-dimethylformamide (30 mL) was added a solution of methyl 1H-indazole-3-carboxylate in N,N-dimethylformamide (20 mL) at room temperature. After stirring for 30 min, bromocyclobutane (3.45 g, 25.5 mmol) was added, and the mixture was stirred at 90° C. for 13 h. After cooling to room temperature, the mixture was poured onto saturated aqueous sodium hydrogencarbonate solution (200 mL), and the aqueous layer was extracted with ethyl acetate/toluene (3:1, 200 mL×2). The combined organic layer was dried over magnesium sulfate, and concentrated under reduced pressure. The residue was chromatographed on a column of silica gel eluting with ethyl acetate/n-hexane (1:6 then 1:5) to give 2.21 g (56%) of the title compound as a colorless oil.

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