2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane → 4-[(ethylthio)methyl]-1-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

Participants

Reaction Steps

To a solution of 4-[(ethylthio)methyl]-1-methyl-1H-pyrazole (0.81 g, 5.2 mmol) in tetrahydrofuran (3.0 mL) at 0° C. was added 1.6 M n-butyllithium in hexane (6.3 mL, 10. mmol). The solution was stirred at room temperature for 1 h and then cooled down to −78° C. To the solution was added 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2.06 mL, 10.1 mmol). The reaction was continued at −78° C. for 0.5 h, then warmed up to 0° C. (taking about 0.5 h). The reaction mixture was quenched with brine, adjusted to PH=6-7 with 1 N HCl aqueous solution, extracted with EtOAc (2×). The combined organic phases were washed with brine, dried over Na2SO4, and concentrated under reduced pressure to give one oil residue which was purified by combi-flash chromatography eluted with EtOAc/hexane (20-100%). The purification gave 1.2 g (86% yield) of the desired product as yellowish oil. LC-MS found: 283.1 (M+H)+.

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