1: thionyl chloride / 2.5 h / Heating 2: diethyl ether / 4 h / Ambient temperature 3: 1.) sec-BuLi, TMEDA, trimethylborate; 2.) Br2 / 1.) THF, -78 deg C, 20 min; -78 deg C to 0 deg C, 1 h; 2.) THF, 0.5 h, RT View Scheme

1: diethyl ether / 4 h / Ambient temperature 2: 1.) sec-BuLi, TMEDA, trimethylborate; 2.) Br2 / 1.) THF, -78 deg C, 20 min; -78 deg C to 0 deg C, 1 h; 2.) THF, 0.5 h, RT View Scheme

boric acid trimethyl ester; N,N,N',N,-tetramethylethylenediamine; bromine; sec.-butyllithium 1.) THF, -78 deg C, 20 min; -78 deg C to 0 deg C, 1 h; 2.) THF, 0.5 h, RT; Yield given. Multistep reaction;