Demethylaromatization of cyclohexadienones by iodotriphenylphosphonium iodide

A highly efficient and metal-free demethylation and concomitant aromatization of cyclohexadienones using iodotriphenylphosphonium iodide was developed. A variety of steroidal and non-steroidal substrates smoothly underwent demethylaromatization reaction generating the corresponding phenolic products in good yields. This approach exhibits broad functional group tolerance. An ionic mechanism of synergistic action was proposed. This method shows potential industrial value in the one-step transformation of 1,4-androstadiene-3,17-dione into 3-hydroxy-1,3,5(10)-estratrien-17-one which serves as a key precursor to a series of steroidal contraceptives.