Hydrochloric Acid → 9-Phenyl-9H-carbazole-3-boronic acid

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Reaction Conditions

Reaction Steps

Into a 500 mL three-neck flask were put 10 g (31 mmol) of 3-bromo-9-phenyl-9H-carbazole, and the air in the flask was replaced with nitrogen. After the replacement, 150 mL of tetrahydrofuran (THF), which was a solvent, was put into the flask and 3-bromo-9-phenyl-9H-carbazole was dissolved. This solution was cooled down to −80° C. Into this solution was dropped 20 mL (32 mmol) of n-butyllithium (a 1.58 mol/L hexane solution) with a syringe. After the dropping, the solution was stirred at the same temperature for 1 hour. After the stirring, 3.8 mL (34 mmol) of trimethyl borate was added to the solution, and the solution was stirred for about 15 hours while the temperature of the solution was being raised to room temperature. After the stirring, about 150 mL of diluted hydrochloric acid (1.0 mol/L) was added to the solution, and then the solution was stirred for 1 hour. After the stirring, an organic layer is separated from the mixture, the aqueous layer was extracted from the mixture with ethyl acetate, and the extracted solution and the organic layer were combined and washed with saturated sodium bicarbonate. The combined organic layer was dried with magnesium sulfate. After the drying, the mixture was subjected to gravity filtration. The obtained filtrate was condensed to give an oily light brown substance. The obtained oily substance was dried under reduced pressure to give 7.5 g of a light brown solid, which was the object of the synthesis, in a yield of 86%. A synthesis scheme of Step 1 is shown in (a-1) given below.

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