Review of chemical syntheses of 7-keto-delta5-sterols

Allylic oxidation of steroidal olefins by vanadyl acetylacetonate and tert-butyl hydroperoxide

Readily available vanadyl acetylacetonate was found to oxidize the allylic sites of Δ(5) steroidal alcohols without protection of hydroxyl groups. Cholesterol, dehydroepiandrosterone, cholesterol benzoate, cholesterol acetate, pregnenolone, and 5-pregnen-3,20-diene were oxidized to 7-keto products using vanadyl acetylacetonate in one pot reactions at room temperature in the presence of oxygen and water.

Bismuth(III) reagents in steroid and terpene chemistry

Steroid and terpene chemistry still have a great impact on medicinal chemistry. Therefore, the development of new reactions or “greener” processes in this field is a contemporaneous issue. In this review, the use of bismuth(III) salts, as “ecofriendly” reagents/catalysts, on new chemical processes involving steroids and terpenes as substrates will be focused. Special attention will be given to some mechanistic considerations concerning selected reactions.

An effective method for allylic oxidation of Delta5-steroids using tert-butyl hydroperoxide

An allylic oxidation method for Delta(5)-steroids using TBHP as oxidant with a 2-quinoxalinol salen Cu(II) complex as catalyst is reported. A variety of Delta(5)-steroidal substrates are selectively oxidized to the corresponding enones. Excellent yields are achieved (up to 99% under optimized conditions) while significantly reducing reaction times required as compared to other current methods.

Optimal TBHP allylic oxidation of Delta5-steroids catalyzed by dirhodium caprolactamate

Dirhodium caprolactamate is the most efficient catalyst for the oxidation of Delta5-steroids to 7-keto-Delta5-steroids by 70% tert-butyl hydroperoxide in water (T-HYDRO). Isolated product yields range from 38 to 87%.