Tamás E. Gunda and Gabriella N. Szőke:
Reactions of Cephalosporin Sulphones 2. Rearrangement of 2α-bromocephem sulphones to pyrroles
Tetrahedron 54, 6565 (1998)

Abstract: 2α-Bromocephem sulphones exhibit two different rearrangements in acetonitrile solution: first, the tendency for elimination of the bromine as a bromonium ion leads to its formal movement to the para position of the 7ß-aromatic ring. Secondly, a bromopyrrole derivative may also form, which can possibly be attributed to an unusual Ramberg-Bäcklund-like rearrangement followed by bromination.