REACTION OF ACID ANHYDRIDES .4. STEROIDAL 3-TRICHLOROACETOXY-DELTA3,5-DIENES - A SIMPLE DECONJUGATION OF DELTA4-3-KETONES

Steroidal Δ4-3-ketones 1, 4 and 5 react with trichloroacetic anhydride resulting in 3-trichloroacetoxy-Δ3,5-dienes 2, 6 and 7. Spectroscopic or other slightly basic methanol converts the 3-trichloroacetoxy-dienes 2 and 7 into the corresponding Δ5-3-ketones 3 and 8. The rate of its methanolysis is much faster than that of the isomerization reaction of the resulting Δ5-3-ketones 3 and 8 to the more stable Δ4-ketones 1 and 5. The methanolysis of the 3-acetoxy-diene 16 may also result in primary formation of the Δ5-3-ketone 3c, but since the rate of its formation is comparable to that of its isomerization to the Δ4-3-ketone, the former compound is not isolable. The Δ4,6-3-ketones 10 and 14 also give 3-trichloroacetoxy-Δ3,5,7-trienes 11 and 15, the former yielding on methanolysis a mixture of the Δ5,7-3-ketone 12, and the Δ3,7-3-ketone 13. © 1969.