Deconjugation of α,β-unsaturated ketones

✍ Scribed by Howard J. Ringold; Sudarshan K. Malhotra

• Publisher: Elsevier Science
• Year: 1962
• Tongue: French
• Weight: 192 KB
• Volume: 3
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)70930-0

✦ Synopsis

BIRCH' demonstrated in 1950 that a steroidal a,p-unsaturated ketone (I) may be deconjugated to its p,y-unsaturated ketone isomer (III) by irreversible protonation of the conjugate anion (II), however, the requisite anion has been prepared only by indirect means (e.g. through the enol acetate, 132 from 4 a 6-bromo-A -3-ketone, 3 or by lithium-ammonia reduction of a A 496 -diene-3-one4). An attempt1 to convert A4-cholestenone to the A'-3-one (III) by treatment with potassium amide in liquid ammonia followed by protonation gave only the A4-j-one presumably because of preferential formation of the C-2 ani0n.l We have found that deconjugation may be readily effected by acetic acid protonation of the anion derived from treatment of A4-3-keto steroids with potassium t-butoxide in t-butanol. Alhtough this base and solvent system have been extensively utilized for C-4 alkylation 5 of steroids and more recently for air oxidation6 it had not been obvious that a high concentration of steroid anion would be present at any given time.