A solution of 5-chloro-2-methoxyphenylboronic acid (10.0 g, 53.6 mmol) in dichloromethane (100 ml) was cooled to a temperature of 5-10C. 100 ml of was added dropwise to the above mixture over a period of 30 min using a homogeneous pressure dropping funnel
1M DCM solution of boron tribromide. The resulting reaction mixture was then stirred at room temperature for 30 minutes. After completion of the reaction, the mixture was poured dropwise into ice-cold saturated sodium bicarbonate solution (600 ml). The resulting mixture was allowed to stir at room temperature for 1 hour. The DCM layer was separated and the aqueous layer thus collected was cooled to a temperature of 10-15C. A 1N dilute hydrochloric acid solution was then added to the above cooled aqueous layer and this led to the formation of a precipitate. The solid was filtered out under vacuum and dried to provide 9 g (97% yield) of product.
