Regioselective dehydrogenation of 3-keto-steroids to form conjugated enones using o-iodoxybenzoic acid and trifluoroacetic acid catalysis

Highlight
• Steroidal conjugated enones were prepared from 3-keto-steroids.
• Dehydrogenation was attained with o-iodoxybenzoic acid and trifluoroacetic acid.
• 3-Keto-5α-steroids yielded the corresponding Δ1-3-keto-steroids regioselectively.
• 3-Keto-5β-steroids gave the corresponding Δ4-3-keto-steroids exclusively.

Mild and regioselective conversion of 3-keto-5α- and 3-keto-5β-steroids (trans A/B- and cis A/B-ring juncture, respectively) to the corresponding enones (Δ1- and Δ4-3-ketones) by treatment with o-iodoxybenzoic acid (IBX) catalyzed by trifluoroacetic acid (TFA) in DMSO, is described. The IBX-mediated reaction involved dehydrogenation of the α- and β-hydrogen atoms of the 3-ketones to give the enones regioselectively in good isolated yields without concomitant formation of related dienones and trienones.