scholarly journals Electrochemical Bromination of Glycals

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhao-Xiang Luo ◽  
Miao Liu ◽  
Tian Li ◽  
De-Cai Xiong ◽  
Xin-Shan Ye
Keyword(s):  
Cyclic Voltammetry ◽  
High Efficiency ◽  
Reaction Process ◽  
Metal Catalyst ◽  
Sonogashira Coupling ◽  
Reaction Conditions ◽  
Radical Trapping ◽  
Protective Groups ◽  
Ferrier Rearrangement ◽  
One Step

Herein, the convenient one-step electrochemical bromination of glycals using Bu4NBr as the brominating source under metal-catalyst-free and oxidant-free reaction conditions was described. A series of 2-bromoglycals bearing different electron-withdrawing or electron-donating protective groups were successfully synthesized in moderate to excellent yields. The coupling of tri-O-benzyl-2-bromogalactal with phenylacetylene, potassium phenyltrifluoroborate, or a 6-OH acceptor was achieved to afford 2C-branched carbohydrates and disaccharides via Sonogashira coupling, Suzuki coupling, and Ferrier rearrangement reactions with high efficiency. The radical trapping and cyclic voltammetry experiments indicated that bromine radicals may be involved in the reaction process.

Electrochemical Mechanism for the Preparation of Fe-Si Alloys by Melts Electrodeposition

2019 ◽  
Vol 18 (2) ◽  
Author(s):  
Hui Li ◽  
Dongbin Wang ◽  
Jing-long Liang ◽  
Hong-yan Yan ◽  
Zong-ying Cai ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Method ◽  
Deposition Time ◽  
Experimental Results ◽  
Reaction Process ◽  
Thermodynamic Calculations ◽  
Pt Electrode ◽  
One Step ◽  
Electrochemical Mechanism ◽  
Cyclic Voltammetry Data

Abstract The melts dissolution characteristics and reaction process during the preparation of Fe-Si alloys by the melts electrochemical method were studied. The thermodynamic calculations and experimental results showed that the solubility of SiO2 in KCl-NaCl-NaF melts was 0.24 mas% at 1073 K. The cyclic voltammetry data showed that the reduction of SiO2 on a Pt electrode was a one-step electron process; when SiO2 accounted for 0.24 mas% of the NaCl-KCl-NaF melts, the Fe-Si alloy was prepared by electrodeposition at 1073 K. When the deposition time was 30 min, Fe3Si was formed.

Micelle-Mediated Chemistry in Water for the Synthesis of Drug Candidates

Synthesis ◽  
2019 ◽  
Vol 51 (13) ◽  
pp. 2632-2647 ◽  
Author(s):  
Alan Steven
Keyword(s):  
Pharmaceutical Industry ◽  
Transition Metal ◽  
Critical Evaluation ◽  
Metal Catalyst ◽  
Catalyst Loading ◽  
Sonogashira Coupling ◽  
Reaction Conditions ◽  
Transition Metal Catalyst ◽  
Drug Candidates ◽  
Nitro Reduction

Micellar reaction conditions, in a predominantly aqueous medium, have been developed for transformations commonly used by synthetic chemists working in the pharmaceutical industry to discover and develop drug candidates. The reactions covered in this review are the Suzuki–Miyaura, Miyaura borylation, Sonogashira coupling, transition-metal-catalysed CAr–N coupling, SNAr, amidation, and nitro reduction. Pharmaceutically relevant examples of these applications will be used to show how micellar conditions can offer advantages in yield, operational ease, amount of waste generated, transition-metal catalyst loading, and safety over the use of organic solvents, irrespective of the setting in which they are used.1 Introduction2 Micelles as Solubilising Agents3 Micelles as Nanoreactors4 Designer Surfactants5 A Critical Evaluation of the Case for Chemistry in Micelles6 Scope of Review7 Suzuki–Miyaura Coupling8 Miyaura Borylation9 Sonogashira Coupling10 Transition-Metal-Catalysed CAr–N Couplings11 SNAr12 Amidation13 Nitro Reduction14 Micellar Sequences15 Summary and Outlook

scholarly journals Fulvene mit inverser Ringpolarisation, 17 [1] Heptafulvene und Heptafulvenradikalkationen: Ringverengung durch Abspaltung eines C1-Fragments bei der Einelektronen-Oxidation von Bis(dimethylamino)dibenzoheptafulven

1984 ◽  
Vol 39 (11) ◽  
pp. 1586-1592 ◽  
Author(s):  
Jörg Daub ◽  
Erika Pirzer ◽  
Christa Trieschmann ◽  
Andreas Merz
Keyword(s):  
Cyclic Voltammetry ◽  
Carboxylic Acid ◽  
Radical Cation ◽  
Acid Amide ◽  
Spectroscopic Methods ◽  
Carboxylic Acid Amide ◽  
Reaction Conditions ◽  
H Nmr ◽  
Radical Trapping

Abstract Disubstituted dibenzoheptafulvenes 4 are obtained from dibenzocycloheptene 8 via the carboxylic acid amide 10, and are characterized by spectroscopic methods and cyclic voltammetry. These dibenzoheptafulvenes are nonplanar, geometric enantiomorphy is shown by 1H-NMR of 12-dim ethyl-am ino-12-siloxydibenzoheptafulvene 4c. Oxidation o f 12,12-bis(dim ethylamino)dibenzo[a,d]-heptafulvene 4a with Ag(I), I2 or Cu(II) leads to the radical cation 7. In solution 7 is converted to dibenzocycloheptatriene and anthracene amidinium salts 18 and 19. The ratio o f these two amidinium salts depends on the reaction conditions. H-radical trapping from the medium is proposed for the formation of 18, while 19 must be formed under elimination of a C1-unit.

scholarly journals Thiocyanation of α-amino carbonyl compounds for the synthesis of aromatic thiocyanates

2020 ◽  
pp. 174751982092355
Author(s):  
Niannian Yi ◽  
Mingjing Ouyang ◽  
Huimin Liu ◽  
Miao Yan ◽  
Xiaoyong Wen ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Transition Metal ◽  
Dimethyl Sulfoxide ◽  
Carbonyl Compounds ◽  
High Efficiency ◽  
Potassium Thiocyanate ◽  
Metal Catalyst ◽  
Reaction Conditions ◽  
Transition Metal Catalyst ◽  
Related Literature

A procedure for K2S2O8-mediated thiocyanation of α-amino carbonyl compounds has been developed for the synthesis of aromatic thiocyanates. A series of α-amino carbonyl compounds have been investigated, and the desired products are obtained in 74%–93% yields. This strategy has the advantages of simple reaction conditions without use of a transition-metal catalyst, high regioselectivity, and high efficiency. Moreover, we found that arylamine thiocyanates can also be obtained from α-amino carbonyl compounds and potassium thiocyanate in the presence of CoCl2·6H2O, I2, and dimethyl sulfoxide through the cleavage of the C–N bond. To explore the reaction mechanism, we designed several control experiments and proposed a possible mechanism using the experimental results and related literature reports.

Direct Cyclization of Alkenyl Thioester via Transition Metal‐hydrogen Atom Transfer/radical‐polar Crossover Mechanism

2019 ◽  
Author(s):  
Shiori Date ◽  
Kensei Hamasaki ◽  
Karen Sunagawa ◽  
Hiroki Koyama ◽  
Chikayoshi Sebe ◽  
...  
Keyword(s):  
Natural Products ◽  
Hydrogen Atom ◽  
Transition Metal ◽  
Hydrogen Atom Transfer ◽  
Synthetic Method ◽  
Atom Transfer ◽  
Reaction Conditions ◽  
Hydride Hydrogen ◽  
Sulfur Heterocycles ◽  
One Step

<div>We report here a catalytic, Markovnikov selective, and scalable synthetic method for the synthesis of saturated sulfur heterocycles, which are found in the structures of pharmaceuticals and natural products, in one step from an alkenyl thioester. Unlike a potentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. The powerful Co catalysis via a cobalt hydride hydrogen atom transfer and radical-polar crossover mechanism enabled simultaneous cyclization and deprotection. The substrate scope was expanded by the extensive optimization of the reaction conditions and tuning of the thioester unit.</div>

A Facile, Efficient and Selective Deprotection of P - Methoxy Benzyl Ethers Using Zinc (II) Trifluoromethanesulfonate

2019 ◽  
Vol 16 (12) ◽  
pp. 955-958
Author(s):  
Reddymasu Sireesha ◽  
Reddymasu Sreenivasulu ◽  
Choragudi Chandrasekhar ◽  
Mannam Subba Rao
Keyword(s):  
Room Temperature ◽  
Protecting Groups ◽  
Side Reactions ◽  
Reaction Conditions ◽  
Acid Sensitivity ◽  
Time Period ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Last Stage ◽  
Zinc Triflate

: Deprotection is significant and conducted over mild reaction conditions, in order to restrict any more side reactions with sensitive functional groups as well as racemization or epimerization of stereo center because the protective groups are often cleaved at last stage in the synthesis. P - Methoxy benzyl (PMB) ether appears unique due to its easy introduction and removal than the other benzyl ether protecting groups. A facile, efficient and highly selective cleavage of P - methoxy benzyl ethers was reported by using 20 mole% Zinc (II) Trifluoromethanesulfonate at room temperature in acetonitrile solvent over 15-120 min. time period. To study the generality of this methodology, several PMB ethers were prepared from a variety of substrates having different protecting groups and subjected to deprotection of PMB ethers using Zn(OTf)2 in acetonitrile. In this methodology, zinc triflate cleaves only PMB ethers without affecting acid sensitivity, base sensitivity and also chiral epoxide groups.

One-step Separation and Purification of Four Phenolic Acids from Stenoloma chusanum (L.) Ching by Medium-pressure Liquid Chromatography and High-speed Counter-current Chromatography

2019 ◽  
Vol 9 (2) ◽  
pp. 138-143
Author(s):  
Tianyun Li ◽  
Xiling Dai ◽  
Yichen Li ◽  
Guozheng Huang ◽  
Jianguo Cao
Keyword(s):  
Natural Products ◽  
Liquid Chromatography ◽  
Phenolic Acids ◽  
High Speed ◽  
High Efficiency ◽  
Total Phenolic ◽  
Medium Pressure ◽  
Medium Pressure Liquid Chromatography ◽  
One Step ◽  
Counter Current

Background:Stenoloma chusanum (L.) Ching is a Chinese traditional medicinal fern with high total flavonoid and total phenolic content. Traditionally, phenolic compounds were separated by using column chromatography, which is relatively inefficient. </P><P> Objective: This study aims to use an efficient method to separate natural products from S. chusanum by Medium-Pressure Liquid Chromatography (MPLC) and High-Speed Counter-Current Chromatography (HSCCC).Methods:In the present research, firstly, a sample (2.5 g) from the dichloromethane extract of S. chusanum was separated by MPLC. Next, fraction P5 was purified by HSCCC with a two-phase solvent system composed of hexane-ethyl acetate-methanol-water (HEMWat) at a volume ratio of 2:4:1:4 (v/v/v/v). </P><P> Result: Four phenolic acids were obtained and their structures were identified by means of NMR and ESI-mass analysis. They were identified as: 1) protocatechuic acid (34 mg, purity 90.1%), 2) syringic acid (66 mg, purity 99.0%), 3) p-hydroxybenzoic acid (5 mg, purity 91.2%) and 4) vanillic acid (6 mg, purity 99.3%).Conclusion:The combination of MPLC and HSCCC is a high-efficiency separation method for natural products. This is the first report with regard to the separation of four phenolic acids in one step by MPLC and HSCCC from S. chusanum (L.) Ching.

Well-designed honeycomb Co3O4@CdS photocatalyst derived from cobalt foam for high-efficiency visible-light H2 evolution

2021 ◽  
Author(s):  
Chao Zhang ◽  
Baoquan Liu ◽  
Weiping Li ◽  
Xiangxue Liu ◽  
Ke Wang ◽  
...  
Keyword(s):  
Visible Light ◽  
Water Splitting ◽  
High Efficiency ◽  
H2 Evolution ◽  
One Step

Well-designed honeycomb Co3O4@CdS (H-Co3O4@CdS) was fabricated via a one-step strategy for efficient water splitting. During the decoration of CdS, honeycomb Co3O4 (H-Co3O4) with macropore was formed simultaneously. H-Co3O4 could enhance...

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