Hydrochloric Acid → 4,4'-Bidibenzothiophene-6-boronic acid

Participants

Reaction Conditions

Reaction Steps

Into a 500-mL three-neck flask was put 5.0 g (13 mmol) of 4,4′-bidibenzothiophene, and the air in the flask was replaced with nitrogen. Into this flask was put 100 mL of tetrahydrofuran (THF), and this solution was cooled down to −80° C. To this solution, 8.7 mL (14 mmol) of n-butyllithium (a 1.6 mol/L hexane solution) was dripped with a syringe. After the dripping, this solution was stirred for 2 hours while its temperature was returned to room temperature. After the stirring, this solution was cooled down to −80° C. To this solution, 1.9 mL (17 mmol) of trimethyl borate was added, and the mixture was stirred for 18 hours while its temperature was returned to room temperature. After the stirring, approximately 50 mL of dilute hydrochloric acid (1.0 mol/L) was added to this solution, followed by stirring for 1 hour. After the stirring, the aqueous layer of this mixture was extracted with ethyl acetate, and the extracted solution 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 with magnesium sulfate, and then this mixture was gravity-filtered. The resulting filtrate was concentrated to give a white solid. This solid was washed with 100 mL of hot toluene to give 2.6 g of white powder, which was an objective substance, in 50% yield. Synthesis Scheme (a-2) of Step 2 is shown below.

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