cooled to 78 u00b0 c under nitrogen atmosphere and added 125 ml of 1 6 m n butyl lithium 200 mmol dropwise through dropping funnel in 1 hr the reaction mixture was stirred at 78 u00b0 c for 1 hr and then gradually warmed up to room temperature after stirred at room temperature for 30 minutes the mixture was again cooled to 78 u00b0 c and added dropwise an ether 50 ml solution of 37 0 g 200 mmol of triisopropyl borate with continual stirring gradually warmed up to room temperature the mixture was stirred at room temperature for another 4 6 hrs after cooled to 0 u00b0 c and added 10 hcl solution the mixture was stirred for 1 hr and then extracted with ether the combined ether extracts were dried with anhydrous mgso 4 and concentrated at room temperature to yield a viscous oil addition of n hexane precipitated dihydroxy 2 furyl borane which was used for the next reaction without further purification 1 h nmr cdcl 3 200 mhz u03b4 4 73 bs 2h 6 45 dd j 1 5 3 3 hz 1h 7 02 d j 3 3 hz 1h 7 61 d j 1 5 hz 1h 120 ml of dimethylformamide 34 dmf 34 was placed in a 2 neck flask equipped with dropping funnel and refluxing condenser and cooled to 20 u00b0 c bromine 0 25 mol was added with stirring stirring was continued for 2 hrs after the addition completed in another 2 neck flask equipped with dropping funnel and refluxing condenser was placed 0 125 mol of furan and 100 ml of dmf the furan solution was heated at 30 40 u00b0 c and dropped in the above prepared bromine solution through the dropping funnel slowly with stirring after addition.