1449-61-2Relevant academic research and scientific papers
Metal-Free Allylic Oxidation of Steroids Using TBAI/TBHP Organocatalytic Protocol
Lam, Ying-Pong,Yeung, Ying-Yeung
, p. 2369 - 2372 (2018)
A mild, efficient and organocatalytic allylic oxidation of steroids using a TBAI/TBHP protocol has been developed. A range of bioactive Δ5-en-7-ones can be easily prepared from the corresponding Δ5-steroids. The methodology features several advantages, including readily available starting materials, environmentally benign oxidant, high functional group compatibility, and metal-free catalysis.
Copper-catalysed allylic oxidation of Δ5-steroids by t-butyl hydroperoxide
Salvador,E Melo,Campos Neves
, p. 119 - 122 (1997)
Δ5-7-Oxosteroids are efficiently prepared from Δ5-steroids with t-BuOOH and a copper catalyst, either Cu(II) and Cu(I) salts or Cu metal; selectivity in the presence of a secondary alcohol is observed.
CrO3/NHPI adsorbed on activated clay: A new supported reagent for allylic selective oxidation of Δ5-sterols
Liu, Jin,Zhu, Hong-You,Cheng, Xiao-Hong
, p. 1076 - 1083 (2009)
Chromium trioxide and N-hydroxyphthalimide (NHPI) supported on activated clay could serve as an efficient and mild oxidant for allylic selective oxidation of Δ5-sterols. Thus, a ketone group could be easily introduced into the allylic position of Δ5-sterols with the existence of a sensitive 3β-hydroxyl group. The oxidant residue can be removed easily from the reaction mixture by filtration and reused after reactivation at 120δC for 4-6 h. Copyright Taylor & Francis Group, LLC.
Recyclable Dirhodium(II) Catalyst Rh2(esp)2 for the Allylic Oxidation of Δ5-Steroids
Wang, Yi,Kuang, Yi,Zhang, Hongyang,Ma, Ruocheng,Wang, Yuanhua
, p. 4729 - 4736 (2017)
The chelating dirhodium(II) catalyst Rh2(esp)2 was shown to efficiently catalyze the allylic oxidation of Δ5-steroids using T-HYDRO (70% tert-butyl hydroperoxide in water) as oxidant. Reaction yields were affected by the coordination ability of the solvent. The noncoordinating solvent n-heptane was determined to be an optimal solvent. At gram scale, the product, Δ5-en-7-one steroid, precipitated from the reaction mixture. The Rh2(esp)2 complex did not undergo catalytic degradation and was recycled using Merrifield-pyridine resin for further allylic oxidation cycles. The results of ultraviolet/visible spectral analysis suggested that the Rh2(II,II) species, rather than the Rh2(II,III) species, was in the catalyst resting state during the reaction, which helps to explain the high durability of the catalyst.
Bismuth-catalyzed allylic oxidation using t-butyl hydroperoxide
Salvador, Jorge A.R.,Silvestre, Samuel M.
, p. 2581 - 2584 (2005)
Bismuth(III) salts are efficient catalysts for the selective allylic oxidation using tert-butyl hydroperoxide. BiCl3 is especially effective and can be easily recovered and reused as BiOCl. Using BiCl 3/K-10 as catalyst, an increase in the reaction rate was observed.
Biohydroxylation of 7-oxo-DHEA, a natural metabolite of DHEA, resulting in formation of new metabolites of potential pharmaceutical interest
?wizdor, Alina,Panek, Anna,Milecka-Tronina, Natalia
, p. 844 - 849 (2016)
Metabolism of steroids in healthy and unhealthy human organs is the subject of extensive clinical and biomedical studies. For this kind of investigations, it is essential that the reference samples of new derivatives of natural, physiologically active steroids (especially those difficult to achieve in the chemical synthesis) become available. This study demonstrated for the first time transformation of 7-oxo-DHEA—a natural metabolite of DHEA, using Syncephalastrum racemosum cells. The single-pulse fermentation of substrate produced two new hydroxy metabolites: 1β,3β-dihydroxy-androst-5-en-7,17-dione and 3β,12β-dihydroxy-androst-5-en-7,17-dione, along with the earlier reported 3β,9α-dihydroxy-androst-5-en-7,17-dione and 3β,17β-dihydroxy-androst-5-en-7-one. Simultaneously, the same metabolites, together with small quantities of 7α- and 7β-hydroxy-DHEA, as well as the products of their reduction at the C-17 were obtained after transformation of DHEA under pulse-feeding of the substrate. The observed reactions suggested that this micro-organism contains enzymes exhibiting similar activity to those present in human cells. Thus, the resulting compounds can be considered as potential components of the eukaryotic, including human, metabolome.
Optimization of the allylic oxidation in the synthesis of 7-keto-Δ5-steroidal substrates
Arsenou, Evaggelia S.,Koutsourea, Anna I.,Fousteris, Manolis A.,Nikolaropoulos, Sotiris S.
, p. 407 - 414 (2003)
A variety of Δ5-steroids were converted into α, β-unsaturated 7-ketones using a modification of the already known method of t-butyl hydroperoxide in the presence of copper iodide in acetonitrile. The same alteration was applied to another oxidative procedure, which had never been used before on steroidal substrates. The same oxidative agent was used in the presence of copper iodide, and tetra-n-butylammonium bromide was used as a phase-transfer catalyst in a two-phase system of water/methylene chloride. It was found that the allylic oxidation proceeded more efficiently when t-butyl hydroperoxide was added to the reaction mixture in portions. The initial addition of the total amount of oxidant or its dropwise addition afforded low yields. This observation contributes to the investigation of the reaction mechanism, and high-yield conversions of steroidal 5,6-enes into the corresponding conjugated 7-ones in short reaction times are reported.
N-Hydroxyphthalimide catalyzed allylic oxidation of steroids with t-butyl hydroperoxide
Zhao, Qian,Qian, Chao,Chen, Xin-Zhi
, p. 1 - 6 (2015)
A new and optimized procedure for the allylic oxidation of Δ5-steroids with t-butyl hydroperoxide in the presence of catalytic amounts of N-hydroxyphthalimide (NHPI) under mild conditions was developed, showing excellent regioselectivity and chemoselectivity (functional group compatibility). It was found that Co(OAc)2 could enhance the catalytic ability of NHPI resulting in better yields and shorter reaction times. The reaction mechanism and the scope of the reaction with a variety of Δ5-steroidal substrates were also investigated.
Visible-Light-Enabled Allylic C-H Oxidation: Metal-free Photocatalytic Generation of Enones
Liu, Chao,Liu, Hui,Zheng, Xuan,Chen, Shanyi,Lai, Qihong,Zheng, Changlong,Huang, Mingqiang,Cai, Kaicong,Cai, Zhixiong,Cai, Shunyou
, p. 1375 - 1381 (2022/02/07)
A practical and efficient method has been established for the direct oxidation of allylic C-H bonds catalyzed by visible-light-enabled photoredox agents. This protocol uses oxygen as the sole oxidant under metal-free conditions at room temperature and pro
Iridium-catalysed highly selective reduction-elimination of steroidal 4-en-3-ones to 3,5-dienes in water
Li, Jide,Tang, Weiping,Ren, Demin,Xu, Jiaxi,Yang, Zhanhui
supporting information, p. 2088 - 2094 (2019/04/29)
Steroidal 3,5-diene is an important structural motif in steroid drugs. In this report, an iridium-catalyzed reduction-elimination of readily available steroidal 4-en-3-ones is realized to prepare steroidal 3,5-dienes. At a low catalyst loading (S/C = 200), heating 4-en-3-ones in a water-mixed organic solvent with formic acid without inert atmosphere protection afforded the desired 3,5-dienes in moderate to excellent yields. In a gram-scale preparation, recrystallization is used instead of column chromatography to purify products. Excellent functionality tolerance and regioselectivity are featured. Structural moieties such as alkanols (primary, secondary and tertiary), esters (except for formate), tolylates, and ketones (endocyclic or exocyclic) are not affected. Surprisingly, the reduction-elimination only takes place at A-ring 4-en-3-ones. In addition, bicyclic 4-en-3-ones are also viable substrates. Synthetic applications of steroidal 3,5-dienes are demonstrated. Our method can also lead to steroidal 3,5-dienes-3-d (>99% d-incorporation) when DCO2D and D2O are used together.
