Synthesis of 11-hydroxylated androstane derivatives

1980 ◽  
Vol 45 (6) ◽  
pp. 1845-1849 ◽  
Author(s):  
Jan Fajkoš ◽  
Jiří Joska
Keyword(s):  
Selective Reduction ◽  
Reaction Conditions ◽  
Androstane Derivatives

Reaction conditions for selective reduction of 3- and 17-oxo groups are described and applied to syntheses of 11-hydroxylated derivatives.

Selective reduction of aromatic alkynes catalyzed by palladium with formic acid as the hydride source

2021 ◽  
Vol 08 ◽  
Author(s):  
Suzanne Chayya ◽  
Mohammad H. El-Dakdouki ◽  
Akram Hijazi ◽  
Ghassan Younes ◽  
Ghassan Ibrahim ◽  
...  
Keyword(s):  
Formic Acid ◽  
Selective Reduction ◽  
Major Product ◽  
Transfer Hydrogenation ◽  
Attractive Alternative ◽  
Unsaturated Ketone ◽  
Partial Reduction ◽  
Reaction Parameters ◽  
Reaction Conditions ◽  
Optimized Conditions

Background: Transfer hydrogenation methods that employ non-H2 hydrogen sources have evolved as an attractive alternative for conventional hydrogenation approaches. Objective: In this study, we aimed at developing optimized conditions to induce the selective transfer hydrogenation reduction of aromatic alkynes catalyzed by PdCl2(PPh3)2 and using formic acid as the hydride source. Methods: The effect of various reaction parameters, such as the nature and amount of the catalyst, the H-donor/base couple, reaction time and temperature, and the nature of the solvent on the outcome of the alkyne reduction were investigated. Results: The reduction of the alkyne can be chemoselectively controlled by adjusting the reaction conditions. Among the tested catalysts, PdCl2(PPh3)2 was the most suitable with 2% of the catalyst being the optimal amount. While the reduction was successful in different solvents of different polarities, THF was selected as the solvent of choice. The reduction of diphenylacetylene yielded the alkene both at 50oC and 80oC. When testing the optimized conditions on the reduction of 4-phenyl-3-butyne-2-one, quantitative partial reduction to the corresponding α,β-unsaturated ketone was obtained at 50oC, while the saturated ketone was produced as the major product at 80oC. Conclusion: The chemoselective reduction of aromatic alkynes was performed successfully with complete conversion using 2% PdCl2(PPh3)2 as a catalyst, formic acid/NEt3 as the H-donor/base couple, THF as the solvent, at 50oC and 80oC.

STEROIDS AND RELATED NATURAL PRODUCTS: XXX. SELECTIVE REDUCTION OF ESTERS. PART A. BENZOATES

1966 ◽  
Vol 44 (11) ◽  
pp. 1283-1291
Author(s):  
George R. Pettit ◽  
Brian Green ◽  
George L. Dunn ◽  
Peter Hofer ◽  
William J. Evers
Keyword(s):  
Natural Products ◽  
Sodium Borohydride ◽  
Boron Trifluoride ◽  
Selective Reduction ◽  
Reaction Conditions ◽  
Benzyl Alcohols ◽  
Type Reaction ◽  
Aliphatic Esters ◽  
Favorable Reaction

Previously, reagents such as sodium borohydride – boron trifluoride were shown to be capable of reducing typical aliphatic esters and lactones to the corresponding ether derivatives. Under the same reaction conditions, a variety of benzoate esters (Ib, IIb, III, and V) were essentially unaffected. Resistance to attack was illustrated by conversion, with sodium borohydride – boron trifluoride, of 3-oxo-17β-benzoyloxy-5α-androstane (III) into 3β-hydroxy-17β-benzoyloxy-5α-androstane (IV) and of reserpine (V) into alcohol VI. With aryl–carbon–oxygen bonds of the ketone VII or alcohol IXa type, reaction with sodium borohydride– boron trifluoride was shown, in general, to cause reductive fission of the benzyl–oxygen linkage (e.g. X → XI). An exception was noted in the case of tertiary benzyl alcohols containing an available β-hydrogen (e.g. IXc). Here, dehydration to yield, for example, olefin XIIb appears to be the more favorable reaction course. The marked difference in the reactivity of sodium borohydride – boron trifluoride toward benzoyl–oxygen vs. benzyl–oxygen bonds has been demonstrated.

scholarly journals Selective reduction of CO to acetaldehyde with CuAg electrocatalysts

2020 ◽  
Vol 117 (23) ◽  
pp. 12572-12575 ◽  
Author(s):  
Lei Wang ◽  
Drew C. Higgins ◽  
Yongfei Ji ◽  
Carlos G. Morales-Guio ◽  
Karen Chan ◽  
...  
Keyword(s):  
Density Functional ◽  
Selective Reduction ◽  
Density Functional Theory Calculations ◽  
Hydrogen Electrode ◽  
Reaction Conditions ◽  
Faradaic Efficiency ◽  
Catalyst Composition ◽  
Alkaline Reaction ◽  
Fuels And Chemicals ◽  
Co Reduction

Electrochemical CO reduction can serve as a sequential step in the transformation of CO2into multicarbon fuels and chemicals. In this study, we provide insights on how to steer selectivity for CO reduction almost exclusively toward a single multicarbon oxygenate by carefully controlling the catalyst composition and its surrounding reaction conditions. Under alkaline reaction conditions, we demonstrate that planar CuAg electrodes can reduce CO to acetaldehyde with over 50% Faradaic efficiency and over 90% selectivity on a carbon basis at a modest electrode potential of −0.536 V vs. the reversible hydrogen electrode. The Faradaic efficiency to acetaldehyde was further enhanced to 70% by increasing the roughness factor of the CuAg electrode. Density functional theory calculations indicate that Ag ad-atoms on Cu weaken the binding energy of the reduced acetaldehyde intermediate and inhibit its further reduction to ethanol, demonstrating that the improved selectivity to acetaldehyde is due to the electronic effect from Ag incorporation. These findings will aid in the design of catalysts that are able to guide complex reaction networks and achieve high selectivity for the desired product.

scholarly journals Highly Selective Reduction of Bio-Based Furfural to Furfuryl Alcohol Catalyzed by Supported KF with Polymethylhydrosiloxane (PMHS)

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zhaozhuo Yu ◽  
Weibo Wu ◽  
Hu Li ◽  
Song Yang
Keyword(s):  
Catalytic System ◽  
Furfuryl Alcohol ◽  
Low Cost ◽  
Selective Reduction ◽  
Reusable Catalyst ◽  
Acid Base ◽  
Reaction Conditions ◽  
Mild Conditions ◽  
Pore Blocking ◽  
Icp Ms

Hydrogenation of bio-based furfural (FUR) to furfuryl alcohol (FFA) is tremendously expanding the application of biomass in many industries such as resins, biofuels, and pharmaceuticals. However, mass manufacture of FFA from FUR is restrained by strict requirements of reaction conditions and expensive catalysts. In this work, an economical and benign catalytic system, containing an easily prepared and reusable catalyst 5 wt.% KF/ZrO2 and a low-cost hydrogen source polymethylhydrosiloxane (PMHS), was developed to be efficient for the hydrogenation of FUR to high-value FFA under mild conditions. The catalyst reactivity was found to be remarkably influenced by the support acid-base properties and KF loading doge. In the presence of 5 wt.% KF/ZrO2, a high FFA yield of 97% and FUR conversion of 99% could be obtained at 25°C in just 0.5 h, which was superior to those attained with other tested catalysts. The KF/ZrO2 catalyst could be recycled at least five times, with the FFA yield slightly decreasing from 97% to 71%. The spare decrease in FFA yield is possibly attributed to the catalyst pore blocking, as clarified by SEM, BET, XPS, and ICP-MS measurements of the fresh and reused catalysts.

Undecagold labeling of tRNA

1991 ◽  
Vol 49 ◽  
pp. 44-45
Author(s):  
James F. Hainfeld ◽  
Kyra M. Alford ◽  
Mathias Sprinzl ◽  
Valsan Mandiyan ◽  
Santa J. Tumminia ◽  
...  
Keyword(s):  
High Resolution ◽  
Transmission Electron Micrograph ◽  
Anticodon Loop ◽  
Electron Micrograph ◽  
Reaction Conditions ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The undecagold (Au11) cluster was used to covalently label tRNA molecules at two specific ribonucleotides, one at position 75, and one at position 32 near the anticodon loop. Two different Au11 derivatives were used, one with a monomaleimide and one with a monoiodacetamide to effect efficient reactions.The first tRNA labeled was yeast tRNAphe which had a 2-thiocytidine (s2C) enzymatically introduced at position 75. This was found to react with the iodoacetamide-Aun derivative (Fig. 1) but not the maleimide-Aun (Fig. 2). Reaction conditions were 37° for 16 hours. Addition of dimethylformamide (DMF) up to 70% made no improvement in the labeling yield. A high resolution scanning transmission electron micrograph (STEM) taken using the darkfield elastically scattered electrons is shown in Fig. 3.

STEROIDSTRUKTUR UND LEBERTOXIZITÄT

1967 ◽  
Vol 54 (1) ◽  
pp. 73-84 ◽  
Author(s):  
H. L. Krüskemper ◽  
G. Noell
Keyword(s):  
Alkaline Phosphatase ◽  
Liver Function ◽  
Blood Coagulation ◽  
Electrophoretic Pattern ◽  
Coagulation Factors ◽  
Blood Coagulation Factors ◽  
Methyl Group ◽  
Liver Functions ◽  
Male Subjects ◽  
Androstane Derivatives

ABSTRACT In male subjects investigations have been carried out regarding the effect of C1- and C17-methylated androstane derivatives (20 mg per day, orally, two weeks) on liver functions (parameters: activities of GPT, GOT, alkaline phosphatase and cholinesterase in serum; electrophoretic pattern; blood coagulation factors V, VII, X and prothrombin; BSP-retention). In addition to the well known hepatotropic action of 17α-alkylated C-19-steroids a quasi-axial 1α-methyl configuration (in 1α-methylandrost-2-en-17β-ol) definitely increased BSP-retention and several coagulation factors. These steroid effects decreased gradually when a methyl group was introduced in C1 equatorially (1-methylandrost-1-en-17β-ol-3-one) or quasi-equatorially (1β-methylandrost-2-en-17β-ol), the latter compound completely lacking from any influence on parameters of liver function under investigation.

Dimensionally-Controlled Hydrothermal Tm3+-doped Oxidic Nanocrystals and Their Photoluminescence Properties

2010 ◽  
Vol 1247 ◽  
Author(s):  
Rocío Calderón-Villajos ◽  
Carlos Zaldo ◽  
Concepción Cascales
Keyword(s):  
Single Crystals ◽  
Fluorescence Lifetimes ◽  
Photoluminescence Properties ◽  
Reaction Conditions ◽  
Hydrothermal Processes ◽  
Bulk Single Crystals ◽  
Template Free ◽  
Reaction Media

AbstractControlled reaction conditions in simple, template-free hydrothermal processes yield Tm-Lu2O3 and Tm-GdVO4 nanocrystals with well-defined specific morphologies and sizes. In both oxide families, nanocrystals prepared at pH 7 reaction media exhibit photoluminescence in ∼1.95 μm similar to bulk single crystals. For the lowest Tm3+ concentration (0.2 % mol) in GdVO4 measured 3H4 and 3F4 fluorescence lifetimes τ are very near to τrad.

Urea-Catalyzed Functionalization of Unactivated C–H Bonds

2020 ◽  
Author(s):  
Alex L. Bagdasarian ◽  
Stasik Popov ◽  
Benjamin Wigman ◽  
Wenjing Wei ◽  
woojin lee ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Organic Synthesis ◽  
High Energy ◽  
Acid Catalysts ◽  
Potential Utility ◽  
New Paradigm ◽  
Lewis Acid Catalysts ◽  
Reaction Conditions ◽  
Highly Active ◽  
Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp<sup>2</sup> carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.<br>

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