p-Sulfonic acid calix[n]arene catalyzed synthesis of bioactive heterocycles: A review

2020 ◽  
Vol 24 ◽  
Author(s):  
Bubun Banerjee ◽  
Gurpreet Kaur ◽  
Navdeep Kaur
Keyword(s):  
Supramolecular Chemistry ◽  
Sulfonic Acid ◽  
Catalytic Efficiency ◽  
The Other ◽  
Reaction Conditions ◽  
Metal Free ◽  
Bioactive Scaffolds ◽  
Wide Range ◽  
Efficient Alternative ◽  
Bioactive Heterocycles

: Metal-free organocatalysts are becoming an important tool for the sustainable developments of various bioactive heterocycles. On the other hand, during last two decades, calix[n]arenes have been gaining considerable attention due to their wide range of applicability in the field of supramolecular chemistry. Recently, sulfonic acid functionalized calix[n] arenes are being employed as an efficient alternative catalyst for the synthesis of various bioactive scaffolds. In this review we have summarized the catalytic efficiency of p-sulfonic acid calix[n]arenes for the synthesis of diverse biologically promising scaffolds under various reaction conditions. There is no such review available in the literature showing the catalytic applicability of p-sulfonic acid calix[n]arenes. Therefore, we strongly believe that this review will surely attract those researchers who are interested about this fascinating organocatalyst.

Deuterated Aryl Alkyl Ethers Synthesis via Nucleophilic Etherification of Aryl Alkyl Ethers and Thioethers with Deuterated Alcohols

Synlett ◽  
2019 ◽  
Vol 30 (15) ◽  
pp. 1805-1809
Author(s):  
Shuai Li ◽  
Xia Wang ◽  
Xin-Ge Yang ◽  
Gui-Quan Yu ◽  
Xue-Qiang Wang
Keyword(s):  
Transition Metal ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Metal Free ◽  
Wide Range ◽  
Alkyl Ethers

A transition-metal-free etherification protocol that is capable of synthesizing deuterated ethers is described. A wide range of aryl alkyl ethers and thioethers were suitable for this transformation owing to the mild reaction conditions. Besides, a series of sterically bulky deuterated alcohols were successfully incorporated into cyano-substituted arenes. The results of mechanistic studies suggested this reaction might take place via nucleophilic aromatic substitution pathway.

scholarly journals Direct access to multi-functionalized benzenes via [4 + 2] annulation of α-cyano-β-methylenones and α,β-unsaturated aldehydes

RSC Advances ◽  
2020 ◽  
Vol 10 (49) ◽  
pp. 29171-29174 ◽  
Author(s):  
Qianfa Jia ◽  
Yunfei Lan ◽  
Xin Ye ◽  
Yinhe Lin ◽  
Qiao Ren
Keyword(s):  
Direct Access ◽  
Reaction Conditions ◽  
Metal Free ◽  
Unsaturated Aldehydes ◽  
Wide Range ◽  
High Yields

An efficient [4 + 2] benzannulation of α-cyano-β-methylenones and α,β-unsaturated aldehydes was achieved under metal-free reaction conditions selectively delivering a wide range of polyfunctional benzenes in high yields respectively (up to 94% yield).

scholarly journals Metal-Free Photoredox Phosphonation of C–N and C–X Bonds in Aqueous Solvent Mixtures

2021 ◽  
Author(s):  
Lei Pan ◽  
Alexandra Kelley ◽  
Maria Victoria Cooke ◽  
Macy Deckert ◽  
Sébastien Laulhé
Keyword(s):  
Building Blocks ◽  
Solvent Mixture ◽  
Solvent Mixtures ◽  
Environmental Footprint ◽  
Reaction Conditions ◽  
Metal Free ◽  
Aqueous Solvent ◽  
Wide Range ◽  
Reaction Proceeds ◽  
Phosphonate Esters

Aryl phosphonate esters are valuable moieties for the pharmaceutical and agrochemical industries. Accessing such compounds from affordable and abundant phosphite reagents and a wide range of aromatic building blocks under metal-free, visible light-induced reaction conditions would represent a desirable technology. Herein, we present an efficient and mild methodology for the synthesis of aromatic phosphonate esters in good to excellent yields using DBU and phenothiazine as a photoredox catalyst. The reaction exhibits wide functional group compatibility enabling the transformation in presence of ketone, amide, ester, amine, and alcohol moieties. Importantly, the reaction proceeds using a green solvent mixture primarily composed of water, thus lowering the environmental footprint of this transformation compared to current methods.

scholarly journals Catalyst-Free, Metal-Free, and Chemoselective Transamidation of Activated Secondary Amides

Synthesis ◽  
2018 ◽  
Vol 51 (04) ◽  
pp. 921-932 ◽  
Author(s):  
Srinivasan Chandrasekaran ◽  
Rajagopal Ramkumar
Keyword(s):  
Amino Acids ◽  
The Other ◽  
Metal Free ◽  
Mild Conditions ◽  
Catalyst Free ◽  
Wide Range ◽  
Simple Protocol ◽  
Secondary Amides ◽  
Free Metal ◽  
Better Than

A simple protocol, which is catalyst-free, metal-free, and chemoselective, for transamidation of activated secondary amides in ethanol as solvent under mild conditions is reported. A wide range of amines, amino acids, amino alcohols, and the substituents, which are problematic in catalyzed transamidation, are tolerated in this methodology. The transamidation reaction was successfully extended to water as the medium as well. The present methodology appears to be better than the other catalyzed transamidations reported recently.

Trichloroisocyanuric Acid Mediated Oxidative Dehydrogenation of Hydrazines­: A Practical Chemical Oxidation To Access Azo Compounds

Synthesis ◽  
2020 ◽  
Vol 52 (07) ◽  
pp. 1103-1112
Author(s):  
Yingpeng Su ◽  
Xuan Liu ◽  
Jie Yu ◽  
Guiyan Cao ◽  
Rong Zhang ◽  
...  
Keyword(s):  
Scale Up ◽  
Chemical Oxidation ◽  
Azo Compounds ◽  
Reaction Conditions ◽  
Metal Free ◽  
Wide Range ◽  
Plausible Mechanism ◽  
Trichloroisocyanuric Acid ◽  
Economical Process ◽  
Operational Simplicity

A highly efficient, metal-free, chemical oxidation of hydrazines has been implemented using environmentally friendly TCCA as oxidant. This benign protocol provides straightforward access to a wide range of azo compounds in THF in excellent yield. Altogether, 35 azo compounds were obtained in this way and scale-up preparations were performed. Additionally, a plausible mechanism was also proposed. Step-economical process, mild reaction conditions, operational simplicity, high reaction efficiency, and easy scale-up highlight the practicality of this methodology.

scholarly journals Bifunctional Iminophosphorane Catalyzed Enantioselective Sulfa-Michael Addition to Unactivated α,β-Unsaturated Amides

2021 ◽  
Author(s):  
Daniel Rozsar ◽  
Michele Formica ◽  
Ken Yamazaki ◽  
Trevor Hamlin ◽  
Darren J. Dixon
Keyword(s):  
Carbonyl Group ◽  
Michael Addition ◽  
Computational Analysis ◽  
Transition States ◽  
Substantial Evidence ◽  
Reaction Conditions ◽  
Metal Free ◽  
Wide Range ◽  
Covalent Activation

<div>The first metal-free catalytic intermolecular enantioselective sulfa-Michael addition to unactivated <i>α</i>,<i>β</i>- unsaturated amides is described. Consistently high enantiomeric excesses, and yields were obtained over a wide range of alkyl thiol pronucleophiles and electrophiles under mild reaction conditions, enabled by a novel squaramide-based bifunctional iminophosphorane (BIMP) catalyst. Low catalyst loadings (2 mol%) were achieved on a decagram scale, demonstrating the scalability of the reaction. Computational analysis revealed the origin of the high enantiofacial selectivity, corresponding transition states, and provided substantial evidence for specific non-covalent activation of the carbonyl group of the <i>α</i>,<i>β</i>-unsaturated amide by the catalyst.</div>

scholarly journals Interaction of 4-{[(tolyl(methane)sulphonyl)oxy]imino}cyclohexa-2,5-dien-1-ones with N-nucleophiles

2021 ◽  
pp. 3-11
Author(s):  
A.P. Avdeenko ◽  
◽  
S.A. Konovalova ◽  
I.Yu. Yakymenko ◽  
V.M. Baumer ◽  
...  
Keyword(s):  
Redox Potential ◽  
Diffraction Data ◽  
Sulfonic Acid ◽  
Biological Activities ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
X Ray ◽  
Wide Range ◽  
Substituted Hydrazines ◽  
Lower Basicity

Hydrazones of 1,4-benzoquinone, which have a wide range of biological activities, can be synthesized in the reactions of 4-{[(arylsulfonyl)oxy]imino}cyclohexa-2,5-diene-1-ones or N-(4-oxocyclohexa-2,5-diene-1-ylidene)arylsulfonamides with N-substituted hydrazines. In this study, the reaction of 2,6-disubstituted 4-{[(tolyl(methane)sulfonyl)oxy]imino}cyclohexa-2,5-diene-1-ones with aroylhydrazides gave N'-(3,5-dialkyl-4-oxocyclohexa-2,5-diene-1-ylidene)aroylhydrazides, which can be obtained by cross-synthesis in the reaction of N-(3,5-dialkyl-4-oxocyclohexa-2,5-dien-1-ylidene)arylsulfonamides with aroylhydrazides. As a result of the reaction of 4-{[(tolyl(methane)sulfonyl)oxy]imino}cyclohexa-2,5-dien-1-ones with phenylhydrazine, stable 4-hydroxyanilinium tolyl(methane)sulfates were isolated. Their structures were confirmed by X-ray diffraction data. We suggested that at the first stage of the reaction between 4-{[(tolyl(methane)sulfonyl)oxy]imino}cyclohexa-2,5-diene-1-ones and hydrazines, the N–O bond of starting 4-(oxyimino)cyclohexa-2,5-diene-1-one was broken forming sulfonic acid and corresponding quinoneimine. The latter either can be reduced to corresponding aminophenol under reaction conditions or can react with an excess of N-substituted hydrazine yielding corresponding hydrazide. The formation of N'-(4-oxocyclohexa-2,5-diene-1-ylidene)arohydrazides is facilitated by a lower basicity of hydrazide and a lower redox potential of quinoneimine.

scholarly journals Bifunctional Iminophosphorane Catalyzed Enantioselective Sulfa-Michael Addition to Unactivated α,β-Unsaturated Amides

2021 ◽  
Author(s):  
Daniel Rozsar ◽  
Michele Formica ◽  
Ken Yamazaki ◽  
Trevor Hamlin ◽  
Darren J. Dixon
Keyword(s):  
Carbonyl Group ◽  
Michael Addition ◽  
Computational Analysis ◽  
Transition States ◽  
Substantial Evidence ◽  
Reaction Conditions ◽  
Metal Free ◽  
Wide Range ◽  
Covalent Activation

<div>The first metal-free catalytic intermolecular enantioselective sulfa-Michael addition to unactivated <i>α</i>,<i>β</i>- unsaturated amides is described. Consistently high enantiomeric excesses, and yields were obtained over a wide range of alkyl thiol pronucleophiles and electrophiles under mild reaction conditions, enabled by a novel squaramide-based bifunctional iminophosphorane (BIMP) catalyst. Low catalyst loadings (2 mol%) were achieved on a decagram scale, demonstrating the scalability of the reaction. Computational analysis revealed the origin of the high enantiofacial selectivity, corresponding transition states, and provided substantial evidence for specific non-covalent activation of the carbonyl group of the <i>α</i>,<i>β</i>-unsaturated amide by the catalyst.</div>

Facile Protocols towards C2-Arylated Benzoxazoles using Fe(III)-Catalyzed C(sp 2-H) Functionalization and Metal-Free Domino Approach

Synlett ◽  
2018 ◽  
Vol 29 (11) ◽  
pp. 1469-1478 ◽  
Author(s):  
Chandi Malakar ◽  
Nagaraju Vodnala ◽  
Raghuram Gujjarappa ◽  
Arup Kabi ◽  
Mohan Kumar ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Drug Discovery ◽  
Precious Metals ◽  
Boronic Acids ◽  
The Other ◽  
Metal Free ◽  
Discovery Research ◽  
Drug Discovery Research ◽  
Wide Range ◽  
High Yields

Considering their growing attention in the field of medicinal chemistry and drug-discovery research, the facile and convenient approaches towards the preparation of 2-aryl benzoxazole derivatives have been described. The transformation is accomplished by using Fe(III)-catalyzed C–H activation of benzoxazoles with boronic acids to obtain a wide range of C2-arylated benzoxazoles in high yields. The developed method excludes the formation of self-coupling compounds as side products. On the other hand, the synthesis of the products is also achieved via a metal-free domino protocol by the reaction between 1-nitroso-2-naphthol and acetophenones using catalytic amounts of CBr4 in the presence of Cs2CO3 as base. The devised tandem method avoids the use of pre-activated α-haloketones as substrates. Due to their immense impact in marketed drugs and molecules under clinical trial, the described method can be a powerful tool for their synthesis which ­restricts the use of precious metals as catalyst.

2D Color-Intensity Representation of Ultrasonic Thickness Gauge Measurements

2020 ◽  
pp. 1192-1198
Author(s):  
M.S. Mohammad ◽  
Tibebe Tesfaye ◽  
Kim Ki-Seong
Keyword(s):  
Cost Effective ◽  
The Other ◽  
Thickness Gauge ◽  
Color Intensity ◽  
Digital Readout ◽  
Flat Surfaces ◽  
Video Cameras ◽  
Wide Range ◽  
Cost Effective Alternative ◽  
Ultrasonic Thickness

Ultrasonic thickness gauges are easy to operate and reliable, and can be used to measure a wide range of thicknesses and inspect all engineering materials. Supplementing the simple ultrasonic thickness gauges that present results in either a digital readout or as an A-scan with systems that enable correlating the measured values to their positions on the inspected surface to produce a two-dimensional (2D) thickness representation can extend their benefits and provide a cost-effective alternative to expensive advanced C-scan machines. In previous work, the authors introduced a system for the positioning and mapping of the values measured by the ultrasonic thickness gauges and flaw detectors (Tesfaye et al. 2019). The system is an alternative to the systems that use mechanical scanners, encoders, and sophisticated UT machines. It used a camera to record the probe’s movement and a projected laser grid obtained by a laser pattern generator to locate the probe on the inspected surface. In this paper, a novel system is proposed to be applied to flat surfaces, in addition to overcoming the other limitations posed due to the use of the laser projection. The proposed system uses two video cameras, one to monitor the probe’s movement on the inspected surface and the other to capture the corresponding digital readout of the thickness gauge. The acquired images of the probe’s position and thickness gauge readout are processed to plot the measured data in a 2D color-coded map. The system is meant to be simpler and more effective than the previous development.

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