Hydroxylation de l''estrone et de son acétate par le peroxyde d''hydrogéne en milieu superacide

Estrone 1a and its acetate 1b react with hydrogen peroxide in SbF₅-HF to give hydroxylated compounds. The formation of the dienone 2 can be accounted for by reaction of the electrophile H₃O₂⁺ on the neutral substrate, whereas formation of compound 3b implies electrophilic attack on the protonated ester 1b. Higher acidity favours rearrangement of the resulting ion 9 to yield, through a spiro intermediate, the ester 4b. Under the reaction conditions esters 3b and 4b]are slowly converted into the corresponding phenols 3a and 4a.