Bromination of Certain Ketosteroids and a Partial Synthesis of Œstradiol, Œstrone and Equilenin

IT has been claimed repeatedly in the literature1 that the conversion of a Δ4-3-ketosteroid (I), for example, testosterone, into a phenol (V), for example, œstradiol, is impossible, because mono- and poly-bromination of (I) leads to compounds possessing halogen atoms in position 4 and in ring B. A reinvestigation of this problem has proved the earlier work in error, and has provided a facile partial synthesis for all of the major, naturally occurring œstrogens.