Acenaphthene-5-boronic acid was prepared as follows: 11.7 g of commercial 5-bromoacenaphthene was dissolved in a solvent mixture of 50 ml of anhydrous toluene and 50 ml of anhydrous ether, and the resulting solution was cooled under argon atmosphere to -40C. 35 ml of a 1.6 M n-butyllithium solution in hexanes was added dropwise to the resulting solution, and the temperature was subsequently raised to -10C. After 2 hours, the resulting solution was cooled to -70C. Another solution made by dissolving 35 ml of triisopropoxyborane in 50 ml of ether was added dropwise to this solution. The resulting solution was stirred at -70C for 3 hours and then left overnight. After overnight, the resulting solution was acidified with 10% by weight of dilute hydrochloric acid and the organic layer was extracted with toluene. The organic layer was washed with dilute hydrochloric acid and saturated sodium chloride solution, dried over anhydrous sodium sulfate, and the organic solvent was distilled using an evaporator. The residue was crystallized using toluene/hexane to give 4.5 g (45% yield) of acenaphthene-5-boronic acid.
