N,N,N',N'-Tetramethylethylenediamine → Naphtho[2,1-b]benzofuran-6-ylboronic acid

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Reaction Conditions

Reaction Steps

After the air in a 500 mL three-neck flask was replaced with nitrogen, 5.8 g (50 mmol) of tetramethylethylenediamine (TMEDA) and 180 mL of tetrahydrofuran (THF) were placed into the flask, and this solution was cooled to −80° C. Then, 50 mL (50 mmol) of sec-butyl lithium (a 1.0 mol/L solution of cyclohexane and n-hexane) was dripped into this solution with a syringe. After that, this solution was stirred at the same temperature for 30 minutes. Then, 10 g (45 mmol) of benzo[b]naphtho[1,2-d]furan dissolved in 70 mL of THF was added dropwise to this solution with a dropping funnel. After that, this solution was stirred at the same temperature for 2 hours. Then, 11 mL (100 mmol) of trimethyl borate was added to this solution, and the mixture was stirred for 2 days while its temperature was returned to room temperature. After that, the aqueous layer of this mixture was subjected to extraction with ethyl acetate, and the obtained solution of the extract and the organic layer were combined and washed with a saturated aqueous solution of sodium hydrogen carbonate and saturated brine. The organic layer was dried over magnesium sulfate, and after that, this mixture was gravity-filtered. The obtained filtrate was concentrated to give a white solid. Toluene/hexane was added to the obtained solid, the mixture was irradiated with ultrasonic waves, and a solid was collected by suction filtration, so that 9.2 g of a white powder of the object of the synthesis was obtained in 78% yield. The above-described synthesis scheme is illustrated in the following scheme (B-3).

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