1912-63-6Relevant academic research and scientific papers
On the Mechanism of Cleavage of Thioacetals Promoted by Copper(II) Sulphate Adsorbed on Silica Gel
Caballero, Gerardo M.,Gros, Eduardo G.
, p. 1147 - 1151 (1997)
A probable mechanism of the cleavage reaction of thioacetals by copper(II) sulphate adsorbed on silica gel involves: formation of a chelate between sulphur atoms and copper(II), previously coordinated with hydroxyl groups on the silica surface, and the subsequent hydrolysis promoted by hydroxyl groups on the silica gel surface.
Sulfur-controlled and rhodium-catalyzed formal (3 + 3) transannulation of thioacyl carbenes with alk-2-enals and mechanistic insights
Wu, Qiuyue,Dong, Ziyang,Xu, Jiaxi,Yang, Zhanhui
, p. 3173 - 3180 (2021/04/21)
A rhodium-catalyzed denitrogenative formal (3 + 3) transannulation of 1,2,3-thiadiazoles with alk-2-enals is achieved, producing 2,3-dihydrothiopyran-4-ones in moderate to excellent yields. An inverse KIE of 0.49 is obtained, suggesting the reversibility of the oxidative addition of thioacyl Rh(i) carbenes to alk-2-enals. The late-stage structural modifications of steroid compounds are realized. Moreover, our studies show that thioacyl carbenes have different reactivities to those of α-oxo and α-imino carbenes, and highlight the importance of heteroatoms in deciding the reactivities of heterovinyl carbenes.
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.
Insights into the synthesis of steroidal A-ring olefins
Varela, Carla L.,Roleira, Fernanda M. F.,Costa, Saul C. P.,Pinto, Alexandra S. C. T.,Martins, Ana I. O. S.,Carvalho, Rui A.,Teixeira, Natercia A.,Correia-Da-Silva, Georgina,Tavares-Da-Silva, Elisiario
, p. 39 - 46 (2014/02/14)
The classical synthesis, followed by purification of the steroidal A-ring Δ1-olefin, 5α-androst-1-en-17-one (5), from the Δ1-3-keto enone, (5α,17β)-3-oxo-5-androst-1-en-17-yl acetate (1), through a strategy involving the reaction of Δ1- 3-hydroxy allylic alcohol, 3β-hydroxy-5α-androst-1-en-17β-yl acetate (2), with SOCl2, was revisited in order to prepare and biologically evaluate 5 as aromatase inhibitor for breast cancer treatment. Surprisingly, the followed strategy also afforded the isomeric Δ2-olefin 6 as a by-product, which could only be detected on the basis of NMR analysis. Optimization of the purification and detection procedures allowed us to reach 96% purity required for biological assays of compound 5. The same synthetic strategy was applied, using the Δ4-3-keto enone, 3-oxoandrost-4-en-17β-yl acetate (8), as starting material, to prepare the potent aromatase inhibitor Δ4-olefin, androst-4-en-17-one (15). Unexpectedly, a different aromatase inhibitor, the Δ3,5-diene, androst-3,5-dien-17-one (12), was formed. To overcome this drawback, another strategy was developed for the preparation of 15 from 8. The data now presented show the unequal reactivity of the two steroidal A-ring Δ1- and Δ4-3- hydroxy allylic alcohol intermediates, 3β-hydroxy-5α-androst-1-en- 17β-yl acetate (2) and 3β-hydroxyandrost-4-en-17β-yl acetate (9), towards SOCl2, and provides a new strategy for the preparation of the aromatase inhibitor 12. Additionally, a new pathway to prepare compound 15 was achieved, which avoids the formation of undesirable by-products. Copyright
Convenient synthesis of monomeric steroids from steroidal oxalate dimers using flash vacuum pyrolysis (FVP)
Nahar, Lutfun,Turner, Alan B.,Sarker, Satyajit D.
experimental part, p. 359 - 366 (2010/11/03)
Flash vacuum pyrolysis (FVP) or thermolysis (FVT), an environmentally friendly method for studying organic reaction mechanisms as well as synthesis, was applied to a series of oxalate dimers (1, 3, 5, 7, 9, 11, 13, and 15) to synthesise monomeric enes, dienes, and a triene (2, 4, 6, 8, 10, 12, 14, and 16). All steroidal monomers were identified by spectroscopic means. TUBITAK.
Preparation of 3,17- and 3,20-difluoro-derivatives of the androst-5-ene and pregn-5-ene series
Decreau, Richard A.,Marson, Charles M.
, p. 4369 - 4385 (2007/10/03)
Unsaturated mono- and difluorosteroids have been prepared in high yield using n-perfluorobutanesulfonyl fluoride 1. The 3,17- and 3,20-difluoro-5,6- dehydrosteroids are reported for the first time. 3-Fluoroderivatives of the androst-5-ene-17-one and 5α-an
The scope and limitations of the reaction of Δ5-steroids with mercury(II) trifluoroacetate
Ruddock, Peter L.D.,Williams, David J.,Reese, Paul B.
, p. 650 - 664 (2007/10/03)
The effect of the C-3 substituent on the reaction of androst-5-enes with mercury(II) trifluoroacetate in dichloromethane (modified Treibs oxidation) was investigated. 3β-Acyloxyandrost-5-en-17-ones gave 3β-acyloxy-6β- hydroxyandrost-4-en-17-ones accompanied by 3β-acyloxy-6- chloromercuriandrost-5-en-17-ones. 3β-Acetoxy-6β-trifluoroacetoxyandrost- 4-en-17-one and 3β-acetoxy-4β-trifluoroacetoxyandrost-5-en-17-one were revealed to be intermediates in the reaction. The formation of the chloromercury steroids indicated participation in the reaction by the solvent. With 3α-acetoxyandrost-5-en-17-one as substrate, a complete reversal in the product distribution was observed. 3β-Haloandrost-5-en-17- ones gave mainly products that reflected S(N)1 substitution of the halide. 3β-Hydroxy- and 3β-trifluoroacetoxyandrost-5-en-17-ones were formed. 3β- Methoxyandrost-5-en-17-one afforded in nearly identical yields androst-4- ene-3,17-dione, 3β-methoxy-6β-hydroxyandrost-4-en-17-one, 3β-methoxy-6- chloromercuriandrost-5-en-17-one and 6β-hydroxyandrost-4-ene-3,17-dione while androst-5-en-17-one yielded 3β,6β-dihydroxyandrost-4-en-17-one, androst-5-ene-7,17-dione and androst-4-ene-3,17-dione. The effects of solvent and other mercury salts on the reaction were also studied. Treibs oxidation was successful in chloroform, carbon tetrachloride, and dibromomethane, but not in other solvents tested. 3β-Acetoxy-6-bromomercuriandrost-5-en-17-one was obtained in dibromomethane. Replacement of the reagent by mercury(II) trichloroacetate altered the intermediates formed but not the products. Mercury(II) tribromoacetate was unreactive, however.
Factors Affecting the Facial Selectivity in the Hydroboration of Steroidal Δ5-Enes
Arantes, Simone F.,Hanson, James R.,Liman, Mansur D.,Manickavasagar, Revathy,Uyanik, Cavit
, p. 2381 - 2397 (2007/10/03)
A comparison between the facial selectivity observed in the hydroboration of some androst-5-enes and B-norandrost-5-enes does not parallel the differences between the calculated force field energies of α- and β-cyclobutane models suggesting that in this case the facial selectivity is not determined by the four centre transition state but by the ease of formation of the initial ?-complexes between the alkene and the borane.
Montmorillonite clay catalysis. Part 31: A new ready and high yield procedure for the cleavage of acetals catalysed by montmorillonite K 10
Li, Tong-Shuang,Li, Sheng-Hui
, p. 2299 - 2303 (2007/10/03)
An easy cleavage of acetals has been carried out in excellent yield under catalysis of montmorillonite K 10 in refluxing wet acetone.
