Tamás E. Gunda and Gabriella N. Szőke:
Regiospecific Bromination of Cephalosporin Sulfones at C-2 with Cyanogen Bromide
Synth. Commun. 27, 3395-3404 (1997)

Abstract: 2α-Bromo-cephalosporin sulfones can be prepared very easily and in practically pure form by using commercial cyanogen bromide with base catalysis. The bromides can immidiately be used for subsequent reactions.