n-butyllithium; HCl in diethyl ether; hexane byproducts: LiCl; ligand soln. cooled to -78°C, treated with n-BuLi in hexane, resulting soln. added to boron compd. soln. in Et2O (1:1), kept for 2 h, dryHCl in Et2O (1 equiv.) added, mixt. heated to room temp., LiCl removed; concd., distilled (80°C, 7 mm Hg);