p-Toluenesulfonic acid → Acetoacetic Acid

Participants

Reaction Steps

If 2β,19-(ethylene)-androst-4-ene-3,17-dione is reduced with sodium borohydride in ethanol, the corresponding Δ4 -3β,17β-diol is obtained. To obtain the Δ5 -3β,17β-diol, the 2β,19-(ethylene)androst-4-ene-3,17-dione is first converted to the corresponding 3-acetoxy-3,5-diene. This conversion is accomplished by treating the dione with acetic anhydride in the presence of a catalytic amount of an acid such as p-toluenesulfonic acid followed by the addition of pyridine, or the conversion can be accomplished by reacting the dione with an excess of acetic anhydride and a catalytic amount of 70% aqueous perchloric acid using ethyl acetate as the solvent followed by neutralization with sodium carbonate. The 3-acetoxy-3,5-diene is then treated with calcium borohydride in ethanol at -15° C. to give the desired Δ5 -diol. Subsequent treatment of the diol with an anhydride, such as acetic anhydride, gives the corresponding diacetate.

Provenance & Evidence