Tetrahydropyranyl ether (THPE) formation in hydroxyl group protection and conversion to other useful functionalities

RSC Advances ◽  
2014 ◽  
Vol 4 (40) ◽  
pp. 21121-21130 ◽  
Author(s):  
Brijesh Kumar ◽  
Mushtaq A. Aga ◽  
Abdul Rouf ◽  
Bhahwal A. Shah ◽  
Subhash C. Taneja
Keyword(s):  
Short Review ◽  
Direct Conversion ◽  
Hydroxyl Group ◽  
Reaction Conditions ◽  
Complex Molecules ◽  
Diverse Range ◽  
Tetrahydropyranyl Ether

This short review highlights the various methods of formation of tetrahydropyranyl ethers (THPEs) as a method for the protection of simple alcohols as well as a diverse range of complex molecules, using a variety of reagents and reaction conditions including their direct conversion to other useful functionalities.

Alkenyl- and aryl[2-(hydroxymethyl)phenyl]dimethylsilanes: Tetraorganosilanes for the practical cross-coupling reaction

2006 ◽  
Vol 78 (2) ◽  
pp. 435-440 ◽  
Author(s):  
Yoshiaki Nakao ◽  
Akhila K. Sahoo ◽  
Hidekazu Imanaka ◽  
Akira Yada ◽  
Tamejiro Hiyama
Keyword(s):  
Functional Groups ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Hydroxyl Group ◽  
Axial Position ◽  
Silyl Ether ◽  
Intramolecular Coordination ◽  
Reaction Conditions ◽  
Diverse Range ◽  
Cross Coupling Reaction

Readily accessible and highly stable alkenyl- and aryl[2-(hydroxymethyl)phenyl]dimethylsilanes cross-couple with various aryl and alkenyl halides under mild reaction conditions employing K2CO3 as a base at 35-80 °C. The reaction tolerates a diverse range of functional groups including silyl protections. The silicon residue, cyclic silyl ether, is readily recovered and reused on a gram-scale synthesis. Intramolecular coordination of a proximal hydroxyl group is considered to efficiently form pentacoordinated silicates having a transferable group at an axial position.

A Facile One-pot Synthesis of Substituted Quinolines via Cascade Friedlander Reaction from Isoxazoles with Ammonium Formate-Pd/C and Ketones

2020 ◽  
Vol 17 (3) ◽  
pp. 211-215
Author(s):  
Da Chen ◽  
Xuan Wang ◽  
Runnan Wang ◽  
Yao Zhan ◽  
Xiaohan Peng ◽  
...  
Keyword(s):  
Hydrogen Transfer ◽  
Ammonium Formate ◽  
Aromatic Ketone ◽  
Reaction Conditions ◽  
One Pot ◽  
Diverse Range ◽  
Strong Base ◽  
Aromatic Ketones ◽  
Substituted Quinolines ◽  
New Strategy

The Friedlander reaction is the most commonly used method to synthesis substituted quinolines, the essential intermediates in the medicine industry. A facile one-pot approach for synthesizing substituted quinolines by the reaction of isoxazoles, ammonium formate-Pd/C, concentrated sulfuric acid, methanol and ketones using Friedlander reaction conditions is reported. Procedures for the synthesis of quinoline derivatives were optimized, and the yield was up to 90.4%. The yield of aromatic ketones bearing electron-withdrawing groups was better than the ones with electron-donating substituents. The structures of eight substituted quinolines were characterized by MS, IR, H-NMR and 13CNMR, which were in agreement with the expected structures. The mechanism for the conversion was proposed, which involved the Pd/C catalytic hydrogen transfer reduction of unsaturated five-membered ring of isoxazole to produce ortho-amino aromatic ketones. Then the nucleophilic addition of with carbonyl of the ketones generated Schiff base in situ, which underwent an intermolecular aldol reaction followed by the elimination of H2O to give production of substituted quinolines. This new strategy can be readily applied for the construction of quinolines utilizing a diverse range of ketones and avoids the post-reaction separation of the o-amino aromatic ketone compounds. The conventionally used o-amino aromatic ketone compounds in Friedlander reaction to prepare substituted quinoline are laborious to synthesize and are apt to self-polymerize. While oxazole adopted in this work can be prepared at ease by the condensation of benzoacetonitrile and nitrobenzene derivatives under the catalysis of a strong base. Moreover, the key features of this protocol are readily available starting materials, excellent functional group tolerance, mild reaction conditions, operational simplicity, and feasibility for scaling up.

scholarly journals Reaction Mechanism for Methane-to-Methanol in Cu-SSZ-13: First-Principles Study of the Z2[Cu2O] and Z2[Cu2OH] Motifs

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 17
Author(s):  
Unni Engedahl ◽  
Adam A. Arvidsson ◽  
Henrik Grönbeck ◽  
Anders Hellman
Keyword(s):  
Liquid Fuel ◽  
Density Functional ◽  
Reaction Pathway ◽  
Direct Conversion ◽  
Reaction Conditions ◽  
Oxidation Of Methane ◽  
Small Pore ◽  
Desorption Step ◽  
Solution Gas ◽  
Stable Motif

As transportation continues to increase world-wide, there is a need for more efficient utilization of fossil fuel. One possibility is direct conversion of the solution gas bi-product CH4 into an energy-rich, easily usable liquid fuel such as CH3OH. However, new catalytic materials to facilitate the methane-to-methanol reaction are needed. Using density functional calculations, the partial oxidation of methane is investigated over the small-pore copper-exchanged zeolite SSZ-13. The reaction pathway is identified and the energy landscape elucidated over the proposed motifs Z2[Cu2O] and Z2[Cu2OH]. It is shown that the Z2[Cu2O] motif has an exergonic reaction path, provided water is added as a solvent for the desorption step. However, a micro-kinetic model shows that neither Z2[Cu2O] nor Z2[Cu2OH] has any notable activity under the reaction conditions. These findings highlight the importance of the detailed structure of the active site and that the most stable motif is not necessarily the most active.

Bu4N+-Controlled Addition and Olefination with Ethyl 2-(Trimethylsilyl)acetate via Silicon Activation

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2401-2406 ◽  
Author(s):  
Donal O’Shea ◽  
Manas Das ◽  
Atul Manvar ◽  
Ian Fox ◽  
Dilwyn Roberts
Keyword(s):  
Room Temperature ◽  
Product Formation ◽  
Unsaturated Ester ◽  
Reaction Conditions ◽  
Diverse Range ◽  
Inorganic Cation ◽  
Tetrabutyl Ammonium ◽  
Aldehydes And Ketones ◽  
Subsequent Elimination ◽  
Hydroxy Esters

Catalytic Bu4NOAc as silicon activator of ethyl 2-(trimethylsilyl)acetate, in THF, was utilized for the synthesis of β-hydroxy esters, whereas employing catalytic Bu4NOTMS gave α,β-unsaturated esters. The established reaction conditions were applicable to a diverse range of aromatic, heteroaromatic, aliphatic aldehydes and ketones. Reactions were achieved at room temperature without taking any of the specialized precautions that are in place for other organometallics. A stepwise olefination pathway via silylated β-hydroxy esters with subsequent elimination to form the α,β-unsaturated ester has been demonstrated. The key to selective product formation lies in use of the weaker acetate activator which suppresses subsequent elimination whereas stronger TMSO– activator (and base) facilitates both addition and elimination steps. The use of tetrabutyl ammonium salts for both acetate and trimethylsilyloxide activators provide enhanced silicon activation when compared to their inorganic cation counterparts.

scholarly journals Intermolecular 3+3 Ring Expansion of Aziridines to Dehydropiperidines through the Intermediacy of Aziridinium Ylides

2019 ◽  
Author(s):  
Jennifer Schomaker ◽  
Josephine Eshon ◽  
Kate A. Nicastri ◽  
Steven C. Schmid ◽  
William T. Raskopf ◽  
...  
Keyword(s):  
Natural Product ◽  
Functional Group ◽  
Ring Expansion ◽  
Sigmatropic Rearrangement ◽  
Reactive Intermediate ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Complex Molecules ◽  
Form Complex ◽  
Reaction Proceeds

Bicyclic aziridines undergo formal [3+3] ring expansion reactions when exposed to rhodium-bound vinyl carbenes to form complex dehydropiperidines in a highly stereocontrolled rearrangement. Mechanistic studies and DFT computations indicate the reaction proceeds through the formation of a vinyl aziridinium ylide; this reactive intermediate undergoes a concerted, asynchronous, pseudo-[1,4]- sigmatropic rearrangement to directly furnish the heterocyclic products with net retention at the new C-C bond. In combination with an asymmetric silver-catalyzed aziridination developed in our group, this method quickly delivers enantioenriched scaffolds with up to three contiguous stereocenters. The mild reaction conditions, functional group tolerance, and high stereochemical retention of this method are especially well-suited for appending piperidine motifs to natural product and complex molecules. Ultimately, our work establishes the value of underutilized aziridinium ylides as key intermediates in strategies to convert small, strained rings to larger N-heterocycles.

Short Review: The Effect of Reaction Conditions on Plant-Mediated Synthesis of Silver Nanoparticles

2018 ◽  
Vol 917 ◽  
pp. 145-151 ◽  
Author(s):  
Nur Syazana Jalani ◽  
Sharifah Zati-Hanani ◽  
Yi Peng Teoh ◽  
Rozaini Abdullah
Keyword(s):  
Silver Nanoparticles ◽  
Bioactive Compounds ◽  
Short Review ◽  
Natural Source ◽  
Hazardous Chemicals ◽  
Reaction Conditions ◽  
Physical Methods ◽  
Stabilizing Agents ◽  
Environmental Friendly ◽  
Source Plant

Recently, interest in plant-mediated synthesis of the silver nanoparticles (AgNPs) is growing among researchers and till now the potential of different plants is still further explored to synthesize nanoparticles. Conventionally, AgNPs are synthesized using chemical and physical methods. However, these methods involve use of toxic and hazardous chemicals which are harmful to health and environment. Therefore, plant-mediated synthesis has been used as environmental friendly alternative to overcome the limitation of conventional methods. The bioactive compounds in plant acts as natural reducing and stabilizing agents which help to increase the rate of synthesis and stabilization of synthesized nanoparticles. Besides, the nanoparticles synthesized using plants are reported to be more stable and the rate of synthesis is much faster compared to other methods. This review focuses on the biosynthesis of AgNPs using plant as natural source plant and the effect of reaction conditions are summarised and discussed.

Palladium-Catalyzed Anti-Markovnikov Oxidation of Aromatic and Aliphatic Alkenes to Terminal Acetals and Aldehydes

Synthesis ◽  
2020 ◽  
Author(s):  
Yasuyuki Ura
Keyword(s):  
Organic Compounds ◽  
Catalytic System ◽  
Recent Progress ◽  
Short Review ◽  
Nucleophilic Attack ◽  
Reaction Conditions ◽  
Terminal Alkenes ◽  
Palladium Catalyzed ◽  
Substrate Addition ◽  
Cyclic Alkenes

AbstractCatalytic anti-Markovnikov (AM) oxidation of terminal alkenes can provide terminally oxyfunctionalized organic compounds. This short review mainly summarizes our recent progress on the Pd-catalyzed AM oxidations of aromatic and aliphatic terminal alkenes to give terminal acetals (oxidative acetalization) and aldehydes (Wacker-type oxidation), along with related reports. These reactions demonstrate the efficacy of the PdCl2(MeCN)2/CuCl/electron-deficient cyclic alkenes/O2 catalytic system. Notably, electron-deficient cyclic alkenes such as p-benzoquinones (BQs) and maleimides are key additives that facilitate nucleophilic attack of oxygen nucleophiles on coordinated terminal alkenes and enhance the AM selectivity. BQs also function to oxidize Pd(0) depending on the reaction conditions. Several other factors that improve the AM selectivity, such as the steric demand of the nucleo­philes, slow substrate addition, and halogen-directing groups, are also discussed.1 Introduction2 Anti-Markovnikov Oxidation of Aromatic Alkenes to Terminal Acetals­3 Anti-Markovnikov Oxidation of Aromatic Alkenes to Aldehydes4 Anti-Markovnikov Oxidation of Aliphatic Alkenes to Terminal Acetals­5 Anti-Markovnikov Oxidation of Aliphatic Alkenes to Aldehydes6 Conclusion

Anodic Oxidation as an Enabling Tool for the Synthesis of Natural Products

Synthesis ◽  
2020 ◽  
Vol 52 (19) ◽  
pp. 2781-2794
Author(s):  
Till Opatz ◽  
Leander Geske ◽  
Eisuke Sato
Keyword(s):  
Organic Synthesis ◽  
Large Scale ◽  
Bond Formation ◽  
Short Review ◽  
Natural Product Synthesis ◽  
Environmentally Benign ◽  
Full Potential ◽  
Future Prospects ◽  
Reaction Conditions ◽  
Chemical Oxidants

Electrochemistry provides a valuable toolbox for organic synthesis and offers an appealing, environmentally benign alternative to the use of stoichiometric quantities of chemical oxidants or reductants. Its potential to control current efficiency along with providing alternative reaction conditions in a classical sense makes electrochemistry a suitable method for large-scale industrial transformations as well as for laboratory applications in the synthesis of complex molecular architectures. Even though research in this field has intensified over the recent decades, many synthetic chemists still hesitate to add electroorganic reactions to their standard repertoire, and hence, the full potential of preparative organic electrochemistry has not yet been unleashed. This short review highlights the versatility of anodic transformations by summarizing their application in natural product synthesis.1 Introduction2 Shono-Type Oxidation3 C–N/N–N Bond Formation4 Aryl–Alkene/Aryl–Aryl Coupling5 Cycloadditions Triggered by Oxidation of Electron-Rich Arenes6 Spirocycles7 Miscellaneous Transformations8 Future Prospects

ChemInform Abstract: Direct Conversion of Tosylhydrazones to tert-Butyl Ethers under Bamford-Stevens Reaction Conditions.

ChemInform ◽  
2010 ◽  
Vol 33 (8) ◽  
pp. no-no
Author(s):  
S. Chandrasekhar ◽  
G. Rajaiah ◽  
L. Chandraiah ◽  
D. Narsimha Swamy
Keyword(s):  
Direct Conversion ◽  
Reaction Conditions ◽  
Tert Butyl
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