Pinacol → 2-(Chloromethyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

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Reaction Steps

To the mixture of triisopropyl borate (15 ml, 65 mmol), chloroiodomethane (13 g, 72 mmol), and tetrahydrofuran (78 ml), n-butyllithium (a 1.6 M n-hexane solution, 41 ml, 65 mmol) was added dropwise at −78° C. (an outer temperature) for 20 min. and then the obtained mixture was stirred at room temperature for 2.5 hours. The reaction mixture was cooled to 0° C. (an outer temperature), and a 4 N hydrochloric acid-ethyl acetate solution was added dropwise thereto at the same temperature until the reaction mixture became neutral. At the same temperature, pinacol (7.7 g, 65 mmol) was added to the reaction mixture, and then the reaction mixture was stirred at room temperature for 40 min. The solvents were evaporated under reduced pressure, and then the obtained residue was distilled under reduced pressure (63-70° C., 11 mmHg), thereby obtaining the entitled compound (9.2 g, 52 mmol, 81%).

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