Selective dehalogenation of 6,6-dibromopenicillanates by indirect electroreduction with diphenyl diselenide as a recyclable mediator

The indirect electroteduction with (PhSe)(2) as a recyclable mediator is ap plied to complete dehalogenation of alpha,alpha -dibromolactams, giving use ful intermediates in the synthesis of beta -lactamase inhibitors. The elect rolysis can be carried out with 2 mol% of (PhSe), in a MeOH/0.2 M NaClO4/(P t) system using a Nafion (R) -separated divided cell. The reaction is consi dered to proceed stepwise by forming mono-debromination products, i.e. alph a bromo-beta -lactams as intermediates, and then further debromination prod ucts. (C) 2001 Elsevier Science B.V. All rights reserved.