ball milling 30-60 min Ar S. F. Nielsen, O. Axelsson, Synth. Commun. 2000, 30, 3501. B(OH) 2 + Br Ac KF-Al 2O 3/ Pd(OAc) 2 ball milling Ar c Franziska Schneider, Org. Proc. Res. & Develop., 2009, 13,44 Up to 96% yield Entry Rpm T (min) Yield% 1 400 10 92 2 800 5 94