scholarly journals Synthesis and Catalytic Activities of 3-Decyl-β-proline for Michael Reactions in Water without an Organic Solvent

ACS Omega ◽  
2021 ◽  
Author(s):  
Kazuhiro Nagata ◽  
Chihiro Nakagawa ◽  
Wakana Yokoyama ◽  
Haruka Usui ◽  
Rikako Mochizuki ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Catalytic Activities ◽  
Michael Reactions

scholarly journals Synthesis of C3-Symmetric Cinchona-Based Organocatalysts and Their Application in Asymmetric Michael and Friedel–Crafts Reactions

2021 ◽  
Author(s):  
Péter Kisszékelyi ◽  
Zsuzsanna Fehér ◽  
Sándor Nagy ◽  
Péter Bagi ◽  
Petra Kozma ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Asymmetric Catalysis ◽  
Michael Reaction ◽  
Supported Catalyst ◽  
Catalyst Recovery ◽  
Catalytic Activities ◽  
Symmetric Structure ◽  
Organic Solvent Nanofiltration ◽  
Positive Effect

In this work, anchoring of cinchona derivatives to trifunctional cores (hub approach) was demonstrated to obtain size-enlarged organocatalysts. By modifying the cinchona skeleton in different positions, we prepared four C3-symmetric size-enlarged cinchona derivatives (hub-cinchonas), which were tested as organocatalysts and their catalytic activities were compared with the parent cinchona (hydroquinine) catalyst. We showed that in the hydroxyalkylation reaction of indole, hydroquinine provides good enantioselectivities (up to 73% ee), while the four new size-enlarged derivatives gave significantly lower values (up to 29% ee) in this reaction. Anchoring cinchonas to trifunctional cores was found to facilitate nanofiltration-supported catalyst recovery using PolarClean alternative solvent. The C3-symmetric size-enlarged organocatalysts were completely rejected by all the applied membranes, whereas the separation of hydroquinine was found to be insufficient using organic solvent nanofiltration. Furthermore, the asymmetric catalysis was successfully demonstrated in the case of Michael reaction of 1,3-diketones and trans-β-nitrostyrene using Hub3-cinchona (up to 96% ee) as a result of the positive effect of the C3-symmetric structure using a bulkier substrate. This means an increased selectivity of the catalyst in comparison to hydroquinine in the latter Michael reaction.

scholarly journals Synthesis of C3-Symmetric Cinchona-Based Organocatalysts and Their Applications in Asymmetric Michael and Friedel–Crafts Reactions

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 521
Author(s):  
Péter Kisszékelyi ◽  
Zsuzsanna Fehér ◽  
Sándor Nagy ◽  
Péter Bagi ◽  
Petra Kozma ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Asymmetric Catalysis ◽  
Michael Reaction ◽  
Supported Catalyst ◽  
Catalyst Recovery ◽  
Catalytic Activities ◽  
Symmetric Structure ◽  
Organic Solvent Nanofiltration ◽  
Positive Effect ◽  
The Michael Reaction

In this work, anchoring of cinchona derivatives to trifunctional cores (hub approach) was demonstrated to obtain size-enlarged organocatalysts. By modifying the cinchona skeleton in different positions, we prepared four C3-symmetric size-enlarged cinchona derivatives (hub-cinchonas), which were tested as organocatalysts and their catalytic activities were compared with the parent cinchona (hydroquinine) catalyst. We showed that in the hydroxyalkylation reaction of indole, hydroquinine provides good enantioselectivities (up to 73% ee), while the four new size-enlarged derivatives resulted in significantly lower values (up to 29% ee) in this reaction. Anchoring cinchonas to trifunctional cores was found to facilitate nanofiltration-supported catalyst recovery using the PolarClean alternative solvent. The C3-symmetric size-enlarged organocatalysts were completely rejected by all the applied membranes, whereas the separation of hydroquinine was found to be insufficient when using organic solvent nanofiltration. Furthermore, the asymmetric catalysis was successfully demonstrated in the case of the Michael reaction of 1,3-diketones and trans-β-nitrostyrene using Hub3-cinchona (up to 96% ee) as a result of the positive effect of the C3-symmetric structure using a bulkier substrate. This equates to an increased selectivity of the catalyst in comparison to hydroquinine in the latter Michael reaction.

STUDIES ON A NON-MELATONIN PINEAL ANTI-GONADOTROPHIN

1972 ◽  
Vol 69 (2) ◽  
pp. 257-266 ◽  
Author(s):  
Bryant Benson ◽  
Mary Jane Matthews ◽  
Alvin E. Rodin
Keyword(s):  
Solvent Extraction ◽  
Organic Solvent ◽  
Pineal Gland ◽  
Gel Filtration ◽  
Test System ◽  
Pineal Body ◽  
Physiological Effects ◽  
Organic Solvent Extraction ◽  
Gland Function

ABSTRACT Continuing investigation of pineal gland function indicates that the anti-gonadotrophic activity of this organ cannot be attributed solely to the postulated hormone melatonin, the concentration of which is negligible in the pineal body compared to quantities required to produce unequivocal physiological effects. A non-melatonin antigonadotrophic substance recently isolated from bovine pineal glands was further purified by organic solvent extraction, ultrafiltration and gel filtration. Studies of partial blockage of compensatory ovarian hypertrophy in unilaterally ovariectomized Charles River CD-1 mice indicated that this substance is significantly more potent than melatonin in this test system.

Photocatalytic activity of TiO2 synthesized by anodization and anodic spark deposition

MRS Advances ◽  
2020 ◽  
Vol 5 (61) ◽  
pp. 3141-3152
Author(s):  
Alma C. Chávez-Mejía ◽  
Génesis Villegas-Suárez ◽  
Paloma I. Zaragoza-Sánchez ◽  
Rafael Magaña-López ◽  
Julio C. Morales-Mejía ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photocatalytic Activity ◽  
Surface Characteristics ◽  
Amorphous Solids ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalytic Activities ◽  
Anodic Spark Oxidation ◽  
Porous Surfaces ◽  
Scanning Electron

AbstractSeveral photocatalysts, based on titanium dioxide, were synthesized by spark anodization techniques and anodic spark oxidation. Photocatalytic activity was determined by methylene blue oxidation and the catalytic activities of the catalysts were evaluated after 70 hours of reaction. Scanning Electron Microscopy and X Ray Diffraction analysis were used to characterize the catalysts. The photocatalyst prepared with a solution of sulfuric acid and 100 V presented the best performance in terms of oxidation of the dye (62%). The electric potential during the synthesis (10 V, low potential; 100 V, high potential) affected the surface characteristics: under low potential, catalyst presented smooth and homogeneous surfaces with spots (high TiO2 concentration) of amorphous solids; under low potential, catalyst presented porous surfaces with crystalline solids homogeneously distributed.

Organic Solvent-Free Reworkable Photocrosslinking System

2007 ◽  
Vol 2 (2) ◽  
pp. 303-306
Author(s):  
Haruyuki Okamura ◽  
Yoshimi Tajima ◽  
Tadahiro Ohba ◽  
Kanji Suyama ◽  
Masamitsu Shirai
Keyword(s):  
Organic Solvent ◽  
Solvent Free

Metal-Assisted Plasma Etching of Silicon: A Liquid-Free Alternative to MACE

2018 ◽  
Author(s):  
Julia Sun ◽  
Benjamin Almquist
Keyword(s):  
Liquid Phase ◽  
Plasma Etching ◽  
Chemical Etching ◽  
Gold Films ◽  
Metallic Films ◽  
Au Catalyst ◽  
Feed Concentration ◽  
Catalytic Activities ◽  
Metal Assisted Chemical Etching ◽  
Complex Nanostructures

For decades, fabrication of semiconductor devices has utilized well-established etching techniques to create complex nanostructures in silicon. Of these, two of the most common are reactive ion etching in the gaseous phase and metal-assisted chemical etching (MACE) in the liquid phase. Though these two methods are highly established and characterized, there is a surprising scarcity of reports exploring the ability of metallic films to catalytically enhance the etching of silicon in dry plasmas via a MACE-like mechanism. Here, we discuss a <u>m</u>etal-<u>a</u>ssisted <u>p</u>lasma <u>e</u>tch (MAPE) performed using patterned gold films to catalyze the etching of silicon in an SF<sub>6</sub>/O<sub>2</sub> mixed plasma, selectively increasing the rate of etching by over 1000%. The degree of enhancement as a function of Au catalyst configuration and relative oxygen feed concentration is characterized, along with the catalytic activities of other common MACE metals including Ag, Pt, and Cu. Finally, methods of controlling the etch process are briefly explored to demonstrate the potential for use as a liquid-free fabrication strategy.

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