Tributyltin Chloride → 1-Methyl-3-tributylstannanyl-1,4,5,6,7,8-hexahydrocycloheptapyrazole

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To a solution of 3-iodo-2-methyl-2,4,5,6,7,8-hexahydrocycloheptapyrazole (180 mg, 0.62 mmol) in THF (3 mL) at −10° C. (ice/acetone) was slowly added isopropylmagnesium chloride (2.0 M in THF, 0.37 mL, 0.74 mmol). The reaction mixture was stirred at −10° C. for 30 min then additional isopropylmagnesium chloride (2.0 M in THF, 0.10 mL, 0.20 mmol) was added. Stirring was continued at −10° C. for 20 min then tributylchlorostannane (0.20 mL, 0.74 mmol) was added dropwise. The reaction mixture was warmed to room temperature and stirred for 1 h then quenched with water and extracted with EtOAc (2×). The organics were dried over MgSO4 and concentrated. The residue was purified by silica gel chromatography with 0% to 10% EtOAc/hexanes (0.5% Et3N spike in hexanes) to afford 76 mg (28%) of 1-methyl-3-tributylstannanyl-1,4,5,6,7,8-hexahydrocycloheptapyrazole as a colorless oil. 1H NMR (CDCl3, 400 MHz): δ (ppm) 3.82 (s, 3H), 2.66-2.76 (m, 2H), 2.50-2.60 (m, 2H), 1.80-1.89 (m, 2H), 1.61-1.74 (m, 4H), 1.51-1.61 (m, 6H), 1.29-1.41 (m, 6H), 1.04-1.12 (m, 6H), 0.91 (t, J=7.3 Hz, 9H).

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