A-ring bromination of estrogens has been achieved by constant current electrolysis of the solutions of these substrates and Et 4 NBr in appropriate solvents. Thus, electrolysis consuming 2 F mol− 1 charge gave mixtures of 2-and 4-estrogens (1: 1.1–2.5; up to 97%), whereas 4 F mol− 1 charge experiments yielded 2, 4-dibromoestrogens as the sole products.
