The Paal-Knorr reaction revisited. A catalyst and solvent-free synthesis of underivatized and N-substituted pyrroles

The Paal-Knorr reaction revisited. A catalyst and solvent-free synthesis of underivatized and N-substituted pyrroles

Green Chem., 2015, Advance Article
DOI: 10.1039/C4GC01523A, Paper
Hyejin Cho, Richard Madden, Bilal Nisanci, Bela Torok
A catalyst and solvent-free room temperature synthesis of pyrroles is described.
A new, modified synthesis of pyrroles is described. The reaction of 2,5-hexandione with a variety of amines yielded the expected pyrrole analogues in excellent yields. The reactions were carried out under the ultimate green conditions excluding both catalyst and solvent applying simple stirring at room temperature. The variety of amines include aqueous ammonium hydroxide for the synthesis of pyrroles with a free NH group, and benzylamines, anilines and phenylene-diamines for the synthesis of several N-derivatized pyrroles. The reaction also occurs efficiently with a variety of 1,4-diketones, although the reaction rates and yields are lower for the diketones that do not possess terminal methyl group(s).
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Eco-friendly synthesis of pyridines via rhodium-catalyzed cyclization of diynes with oximes

Eco-friendly synthesis of pyridines via rhodium-catalyzed cyclization of diynes with oximes

Green Chem., 2015, Advance Article
DOI: 10.1039/C4GC01756K, Communication
Fen Xu, Chunxiang Wang, Haolong Wang, Xincheng Li, Boshun Wan
We describe a new route for the synthesis of pyridines via [2 + 2 + 2] cycloaddition of diynes and oximes catalyzed by Rh(NBD)2BF4/MeO-Biphep using ethanol as an alternative reaction medium, affording the desired pyridine derivatives in yields of up to 93%.
We describe a new route for the synthesis of pyridines via [2 + 2 + 2] cycloaddition of diynes and oximes catalyzed by Rh(NBD)2BF4/MeO-Biphep using ethanol as an alternative green reaction medium, affording the desired pyridine derivatives in yields of up to 93%. This environmentally friendly method meets the requirement for green chemistry by minimizing pollution from solvents and is tolerant of a range of functional groups.

Bronsted acid ionic liquid-catalyzed reductive Friedel-Crafts alkylation of indoles and cyclic ketones without using an external reductant

ORGANIC CHEMISTRY SELECT

Green Chem., 2015, Advance Article
DOI: 10.1039/C4GC01299B, Communication
Amir Taheri, Bingbing Lai, Cheng Cheng, Yanlong Gu
C3-cycloalkylated indole was synthesized from indole and cyclic ketone in the absence of a reductant with the aid of an acid catalyst.
Bronsted acid ionic liquid-catalyzed reductive Friedel-Crafts alkylation of indoles and cyclic ketones without using an external reductant
In the absence of an external reductant, C3-cycloalkylated indole could be synthesized through reductive alkylation of indole with cyclic ketone using a sulfonyl-functionalized Brønsted acid ionic liquid as a catalyst. Water generated in the initial stage of the reaction played a key role in rendering the reductive coupling possible. The reaction proceeds most likely in a radical way.

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Microwave-Assisted Three-Component “Catalyst and Solvent-Free” Green Protocol: A Highly Efficient and Clean One-Pot Synthesis of Tetrahydrobenzo[b]pyrans,

851924.sch.001
Scheme 1: Synthesis of 4H-benzo[b]pyran derivatives under MW irradiation.

 

Microwave-Assisted Three-Component “Catalyst and Solvent-Free” Green Protocol: A Highly Efficient and Clean One-Pot Synthesis of Tetrahydrobenzo[b]pyrans,

Organic Chemistry International
Volume 2014 (2014), Article ID 851924, 8 pages
http://dx.doi.org/10.1155/2014/851924

 

Sougata Santra, Matiur Rahman, Anupam Roy, Adinath Majee, and Alakananda Hajra
Volume 2014 (2014), Article ID 851924, 8 pages

http://www.hindawi.com/journals/oci/2014/851924/

A green and highly efficient method has been developed for the one-pot synthesis of tetrahydrobenzo[b]pyrans via a three-component condensation of aldehydes, 1,3-cyclic diketones, and malononitrile under MW irradiation without using any catalyst and solvent. This transformation presumably occurs by a sequential Knoevenagel condensation, Michael addition, and intramolecular cyclization. Operational simplicity, solvent and catalyst-free conditions, the compatibility with various functional groups, nonchromatographic purification technique, and high yields are the notable advantages of this procedure.

851924.sch.002
Scheme 2: Plausible reaction mechanism.
851924.sch.003

 

A rapid, convenient, solventless green approach for the synthesis of oximes using grindstone chemistry

A rapid, convenient, solventless green approach for the synthesis of oximes using grindstone chemistry
Lakhinath Saikia, Jejiron Baruah, Ashim Thakur
Organic and Medicinal Chemistry Letters 2011, 1:12 (4 October 2011)

http://www.orgmedchemlett.com/content/1/1/12

Background
Synthesis of oximes is an important reaction in organic chemistry, because these versatile oximes are used for protection, purification, and characterization of carbonyl compounds. Nitriles, amides via Beckmann rearrangement, nitro compounds, nitrones, amines, and azaheterocycles can be synthesised from oximes. They also find applications for selective α-activation. In inorganic chemistry, oximes act as a versatile ligand.

Several procedures for the preparation of oximes exist, but, most of them have not addressed the green chemistry issue. They are associated with generation of pollutants, requirement of high reaction temperature, low yields, lack of a generalized procedure, etc. Hence, there is a demand for developing an efficient, convenient, and non-polluting or less polluting alternative method for the preparation of oximes. In this context, bismuth compounds are very useful as they are cheap in general, commercially available, air stable crystalline solids, safe, and non-toxic, hence easy to handle.

Results
Carbonyl compounds (aliphatic, heterocyclic, and aromatic) were converted into the corresponding oximes in excellent yields by simply grinding the reactants at room temperature without using any solvent in the presence of Bi2O3. Most importantly, this method minimizes waste disposal problems, provides a simple yet efficient example of unconventional methodology and requires short time.

Conclusions
We have developed a novel, quick, environmentally safe, and clean synthesis of aldoximes and ketoximes under solvent-free grinding condition.

A truly green synthesis of α-aminonitriles via Strecker reaction

A truly green synthesis of α-aminonitriles via Strecker reaction

Debasish Bandyopadhyay, Juliana M Velazquez, Bimal K BanikOrganic and Medicinal Chemistry Letters 2011, 1:11 (4 October 2011)

Background
The classical Strecker reaction is one of the simplest and most economical methods for the synthesis of racemic α-aminonitriles (precursor of α-amino acids) and pharmacologically useful compounds.Results
Indium powder in water is shown to act as a very efficient catalyst for one-pot, three-component synthesis of α-aminonitriles from diverse amines, aldehydes and TMSCN. This general rapid method is applicable to a wide range of amines and aldehydes and produces products in excellent yield.

Conclusions
The present one-pot, three-component environmentally benign procedure for the synthesis of α-aminonitriles will find application in the synthesis of complex biologically active molecules.

Healthy diets are good for the kidneys

ClinicalNews.Org

Philadelphia, PA (November 15, 2014) — A healthy diet may help protect the kidneys, according to two studies that will be presented at ASN Kidney Week 2014 November 11¬-16 at the Pennsylvania Convention Center in Philadelphia, PA.

Dietary modifications may be a low-cost, simple intervention to reduce the burden of chronic kidney disease (CKD). To test this hypothesis, Andrew Smyth, MD (National University of Ireland Galway) and his colleagues analyzed questionnaires completed by 544,635 participants of the National Institutes of Health-AARP Diet and Health Study that assessed diet quality, as well as sodium and potassium intake.

A higher-quality diet, as measured using 3 different scoring systems for dietary qualities known to reduce the risk of cardiovascular disease, was associated with a 16% to 23% reduced risk of needing dialysis or dying from kidney problems. Higher-quality diets included those high in fruits, vegetables, and unsaturated fats. The researchers also found that…

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