preparation | 5-chloro-2-methoxyphenylboronic acid (10.0g,53.6mmol) in dichloromethane (100ml) the solution was cooled to a temperature of 5-10 °c. 100ml of 1m boron tribromide solution in DCM was added dropwise to the above mixture over a period of 30 minutes using a pressure-equalizing dropping funnel. 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 (600ml). 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 10-15 °c. A 1N dilute hydrochloric acid solution was then added to the cooled aqueous layer as described above, and this resulted in the formation of a precipitate. The solid was filtered off under vacuum and dried to afford 9G (97% yield) of product. |