- Platinum-Catalyzed α,β-Desaturation of Cyclic Ketones through Direct Metal–Enolate Formation
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The development of a platinum-catalyzed desaturation of cyclic ketones to their conjugated α,β-unsaturated counterparts is reported in this full article. A unique diene-platinum complex was identified to be an efficient catalyst, which enables direct metal-enolate formation. The reaction operates under mild conditions without using strong bases or acids. Good to excellent yields can be achieved for diverse and complex scaffolds. A wide range of functional groups, including those sensitive to acids, bases/nucleophiles, or palladium species, are tolerated, which represents a distinct feature from other known desaturation methods. Mechanistically, this platinum catalysis exhibits a fast and reversible α-deprotonation followed by a rate-determining β-hydrogen elimination process, which is different from the prior Pd-catalyzed desaturation method. Promising preliminary enantioselective desaturation using a chiral-diene-platinum complex has also been obtained.
- Chen, Ming,Dong, Guangbin
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supporting information
p. 7956 - 7961
(2021/03/01)
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- A synthesis of 7alpha-hydroxyandrost-4-ene-3,17-dione.
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The first convenient chemical synthesis of 7alpha-hydroxyandrost-4-ene-3,17-dione is reported. Androsta-4,6-diene3, 17-dione was converted into its 6alpha, 7alpha-epoxy-derivative; reduction of the epoxide with aluminum amalgam gave 7alpha-hydroxyandrost-4-ene-3,17-dione. This reducing agent is more efficient than chromous acetate for the purpose.
- Hossain,Kirk,Mitra
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p. 603 - 608,605, 607
(2007/10/12)
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- 3-Keto-7 α,β-loweralkyl-Δ 5-steroids
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7(α,β)-Loweralkyl-3-keto-Δ 5 -androstanes and 7(α,β)-loweralkyl-3-keto-Δ 5 -pregnanes having anabolic, androgenic, claudogenic, progestational and anti-progestational properties are prepared by reacting 3-keto-4,6-dienic androstanes and pregnanes with organocopper reagents such as dialkyllithium cuprate. The isomerization of these compounds to yield 7(α,β)-loweralkyl-3-keto-Δ 4 -steroids is also described.
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