Trimethyl borate → 4-(t-Butoxycarbonylamino)naphthalene-1-boronic acid

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Reaction Conditions

Reaction Steps

In a dry flask under Argon was added butylmagnesium chloride (2.0 M in THF, 2.0 mL, 4.0 mmol) and anhydrous THF (10 mL). The solution was cooled to −5° C. and butyllithium (1.6 M in hexane, 5.0 mL, 8.0 mmol) was added dropwise while the temperature was kept below 0° C. After the resulting solution was stirred at 0° C. for 0.5 h, the temperature was lowered to −5° C. N-Boc-4-bromo-1-aminonaphthalene (0.64 g, 2.0 mmol) was dissolved in anhydrous THF(10 mL) and added dropwise while the temperature was kept below 0° C. The solution was stirred at 0° C. for 0.5 h. HPLC of a sample taken from the solution and quenched with MeOH indicated that no starting material was left. The temperature was lowered to −5° C. and trimethyl borate(2.5 mL, 22.0 mmol) was added slowly. After the mixture was stirred at 0° C. for 2 h, ammonium chloride solution (saturated, 20 mL) was added and the mixture was stirred at 21° C. for 0.5 h. The pH of the mixture was adjusted to 7 with sodium bicarbonate and the mixture was stirred at 21° C. for 18 h. Ethyl acetate (10 mL) was added and the mixture was stirred for 0.5 h. The organic layer was separated and dried with magnesium sulfate. The solvent was removed under vacuum and then hexane (60 mL) was added and the resulting slurry was stirred for 0.5 h. Filtration and hexane (10 mL) wash gave the title compound as a white solid (0.46 g, 80.5% pure, 65% yield).

Provenance & Evidence