Dienone−phenol rearrangement of sulphur-containing derivatives of steroids

Dienone–phenol rearrangement occurs in the reaction of an oxathiolane and dithiolane of 3-oxo-steroids with copper(II) bromide to give 4-methyl-19-norcholesta-1,3,5,(10)-trieno[1,2-b]-dihydroxathiine and -dihydrodithiine, respectively.