A Green Approach for Organic Transformations Using Microwave Reactor

2019 ◽  
Vol 16 (5) ◽  
pp. 730-764 ◽  
Author(s):  
Subrata Das ◽  
Rupak Banik ◽  
Brajesh Kumar ◽  
Subhadip Roy ◽  
Noorussabah ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Microwave Heating ◽  
Organic Synthesis ◽  
Reaction Times ◽  
Green Technology ◽  
Conventional Heating ◽  
Organic Transformations ◽  
Green Approach ◽  
Site Selectivity ◽  
Recent Developments

Microwave-assisted organic transformation (MAOR) is presently gaining wide popularity in the field of organic synthesis. The conventional heating technique is gradually being removed from the laboratory and a novel microwave heating technique established to be used in both academia and industry. As compared to the classical organic methodology, the green technology tools have several advantages like dramatically reduced reaction times, improved yields, site selectivity, and the increased product purities with simplification of work-up procedures. In the current study, we have briefly described the overview of recent developments and applications of microwave irradiation in organic transformation with schematic compiling of the organic reactions, bioactive heterocyclic compounds, and so on. This review also presents a critical analysis of the various advantages of microwave irradiation in organic synthesis/transformation compared to the classical or conventional heating. So, we believe that our current study of the green microwave heating technique will be highly beneficial for the researchers from both academia and industry in their near future.

Regioselective Synthesis of Potent 4,5,6,7-Tetrahydroindazole Derivatives via Microwave-assisted Vilsmeier-Haack Reaction and their Antioxidant Activity Evaluation

2019 ◽  
Vol 16 (3) ◽  
pp. 194-201 ◽  
Author(s):  
Renu Bala ◽  
Vandana Devi ◽  
Pratibha Singh ◽  
Navjot Kaur ◽  
Pawandeep Kaur ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Microwave Irradiation ◽  
Biological Activities ◽  
Reaction Times ◽  
Conventional Heating ◽  
High Chemical ◽  
Microwave Assisted ◽  
Work Up ◽  
Active Methylene ◽  
By Products

Background: Tetrahydroindazole, a member of the fused-pyrazole system, is a least studied class of heterocyclic compounds owing to its scarcity in nature. However, a large number of synthetically prepared tetrahydroindazoles are known to show a variety of biological activities such as interleukin- 2 inducible T-Cell kinase inhibitors, AMPA receptor positive allosteric modulators, antitumor, antituberculosis, anti-inflammatory and antimicrobial activities. Vilsmeier-Haack reaction is one of the most important chemical reactions used for formylation of electron rich arenes. Even though Vilsmeier- Haack reaction was studied on a wide variety of hydrazones derived from active methylene compounds, literature lacks the examples of the use of 4-substituted cyclohexanones as a substrate for the synthesis of 4,5,6,7-tetrahydroindazoles. The study of the reaction of Vilsmeier-Haack reagent with hydrazones derived from cyclic keto compounds having active methylene has been considered the interested topic of investigation. In the present study, ethyl cyclohexanone-4-carboxylate was treated with one equivalent of various hydrazines for two hours and the resulted hydrazones were further treated with an OPC-VH reagent (Vilsmeier-Haack reagent isolated from phthaloyl dichloride and N,Ndimethylformamide) afforded 4,5,6,7-tetrahydroindazoles in excellent yields. The synthesized compounds 4a-f and 5a-f were screened for their antioxidant activities using the DPPH radical scavenging assay. The target compounds were synthesized regioselectively using 4+1 approach in excellent yields. A number of experiments using both conventional heating as well as microwave irradiation methods were tried and on comparison, microwave irradiation method was found excellent in terms of easy work up, high chemical yields, shortened reaction times, clean and, no by-products formation. Some of the synthesized compounds showed significant antioxidant activity. The microwave assisted synthesis of 4,5,6,7-tetrahydroindazoles from ethyl cyclohexanone-4-carboxylate has been reported under mild conditions in excellent yield. Easy work up, high chemical yield, shortened reaction times, clean and no by-products formation are the major advantages of this protocol. These advantages may make this method useful for chemists who are interested in developing novel 4,5,6,7-tetrahydroindazole based drugs.

Efficient Biginelli Synthesis of 2-Aminodihydropyrimidines under Microwave Irradiation

Synlett ◽  
2018 ◽  
Vol 29 (08) ◽  
pp. 1047-1054 ◽  
Author(s):  
Fulvia Felluga ◽  
Fabio Benedetti ◽  
Federico Berti ◽  
Sara Drioli ◽  
Giorgia Regini
Keyword(s):  
Microwave Irradiation ◽  
Guanidine Hydrochloride ◽  
Reaction Times ◽  
Conventional Heating ◽  
Dicarbonyl Compounds ◽  
Simple Protocol ◽  
Twofold Excess ◽  
General Method

A practical and general method for the Biginelli cyclocondensation of guanidine with aldehydes and β-dicarbonyl compounds is described and illustrated with the synthesis of a set of 26 functionalized 2-amino-3,4-dihydropyrimidines. The simple protocol involves the ­microwave-mediated reaction of a twofold excess of guanidine hydrochloride with the required reaction partners in an alcohol at 120 °C. Yields are generally good, with short reaction times and a simple workup. The scope is considerably wider than that of similar reactions ­carried out under conventional heating.

The double and triple role of L-(+)-tartaric acid and dimethyl urea: A prevailing green approach in organic synthesis

2021 ◽  
Vol 25 ◽  
Author(s):  
Rashid Ali ◽  
Ajay Kumar Chinnam ◽  
Vikas R. Aswar
Keyword(s):  
Tartaric Acid ◽  
Organic Synthesis ◽  
Low Cost ◽  
Organic Transformations ◽  
Green Approach ◽  
Dimethyl Urea ◽  
Low Toxicity ◽  
The One ◽  
Near Future

: The deep eutectic mixtures (DESs), introduced as novel alternative to usual volatile organic solvents for organic transformations has attracted a tremendous attention of the research community because of their low cost, negligible vapour pressure, low toxicity, biodegradability, recyclability, insensitive towards moisture, and readily availability from bulk renewable resources. Although, the low melting mixture of dimethyl urea (DMU)/L-(+)-tartaric acid (TA) is still infancy yet much effective as it play double and triple roles such as solvent, catalyst and/or reagent in a same pot for many crucial organic transformations. These unique properties of DMU/TA mixture prompted us to provide a quick overview of where the field stands presently, and where it might be going in near future. To our best knowledge, no review dealing with the applications of a low melting mixture of DMU/TA appeared in the literature except the one published in 2017 describing only the chemistry of indole systems. Therefore, we intended to reveal the developments of this versatile low melting mixture in the modern organic synthesis since its first report in 2011 by Köenig’s team to till date. Hopefully, the present review article will be useful to the researcher working not only in the arena of synthetic organic chemistry but also to the scientists working in other branches of science and technology.

Organic Synthesis

2017 ◽  
Author(s):  
Douglass F. Taber ◽  
Tristan Lambert
Keyword(s):  
Organic Synthesis ◽  
State Of The Art ◽  
Research Area ◽  
Organic Transformations ◽  
The Past ◽  
Catalytic Asymmetric Synthesis ◽  
New Methods ◽  
Recent Developments ◽  
Enantioselective Epoxidation ◽  
To Come

Organic synthesis is a vibrant and rapidly evolving field; chemists can now cyclize alkenes directly onto enones. Like the first five books in this series, Organic Synthesis: State of the Art 2013-2015 will lead readers quickly to the most important recent developments in a research area. This series offers chemists a way to stay abreast of what's new and exciting in organic synthesis. The cumulative reaction/transformation index of 2013-2015 outlines all significant new organic transformations over the past twelve years. Future volumes will continue to come out every two years. The 2013-2015 volume features the best new methods in subspecialties such as C-O, C-N and C-C ring construction, catalytic asymmetric synthesis, selective C-H functionalization, and enantioselective epoxidation. This text consolidates two years of Douglass Taber's popular weekly online column, "Organic Chemistry Highlights" as featured on the organic-chemistry.org website and also features cumulative indices of all six volumes in this series, going back twelve years.

Comparison of Conventional and Microwave Heating for Evaluation of Microwave Effects

2016 ◽  
Vol 69 (8) ◽  
pp. 865 ◽  
Author(s):  
Péter Bana ◽  
István Greiner
Keyword(s):  
Temperature Measurement ◽  
Microwave Heating ◽  
Organic Synthesis ◽  
Convenient Method ◽  
Thermal Effects ◽  
Fibre Optic ◽  
Organic Transformations ◽  
Microwave Assisted ◽  
Microwave Reactor ◽  
Microwave Effects

In microwave-assisted organic synthesis, the question of microwave effects is still debated. Proper examination of these hypothesized phenomena is encumbered by some specific features of microwave heating. We devise a convenient method to eliminate most of the irreproducibility observed in microwave-heated organic transformations by thermal conditioning of the microwave reactor cavity. To show the utility of this approach, we investigated a reaction of 2-chloropyridine, in which microwave conditions were shown to be beneficial by previous studies. Using our method to ensure proper reproducibility together with fibre optic temperature measurement, the observed differences were traced back to large hidden thermal differences, while non-thermal effects could not be detected in the comparison experiments.

Synthesis of anti-inflammatory 2,3-unsaturated O-glycosides using conventional and microwave heating techniques

2017 ◽  
Vol 23 (3) ◽  
pp. 205-211
Author(s):  
Adriana Cristina N. de Melo ◽  
Ronaldo N. de Oliveira ◽  
João R. de Freitas Filho ◽  
Teresinha G. da Silva ◽  
Rajendra M. Srivastava
Keyword(s):  
Reaction Time ◽  
Microwave Irradiation ◽  
Microwave Heating ◽  
Acid Catalyst ◽  
Conventional Heating ◽  
Microwave Exposure ◽  
Ferrier Rearrangement ◽  
Acetyl Group ◽  
Anti Inflammatory

AbstractThe preparation of eight 2,3-unsaturated O-glycosides from D-glycals and alcohols, using montmorillonite K-10 as an acid catalyst, is described. The Ferrier rearrangement products were obtained in good yields using conventional heating and microwave irradiation but the reaction time was substantially reduced employing the latter procedure. The yields were slightly lower under microwave exposure. Five of the di-O-acetylated products were deacetylated to the glycosides in excellent yields. The acetylated products possess good anti-inflammatory property suggesting that the acetyl group plays an important role in reducing the inflammation. Among the compounds tested, glycosides containing thiophene as an aglycone present much better inflammation reducing characteristics than the analogues without this function.

scholarly journals Orthoamide, LXII [1]. – Mikrowellen-unterst ¨ utzte Formylierung schwach CH2-acider Verbindungen mit dem Bredereck-Simchen Reagenz – Umwandlung der Kondensationsprodukte in Heteroaromaten / Orthoamides, LXII [1]. – Microwave Assisted Formylation of Weak CH2-Acidic Compounds with the Bredereck-Simchen Reagent – Preparation of Heteroaromatic Compounds from the Condensation Products

2005 ◽  
Vol 60 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Willi Kantlehner ◽  
Gerhard Simchen ◽  
Jochen Mezger ◽  
Edmont V. Stoyanov ◽  
Ralf Kreß ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Reaction Times ◽  
Conventional Heating ◽  
Methyl Anthranilate ◽  
Prolonged Heating ◽  
Heteroaromatic Compounds ◽  
Microwave Assisted ◽  
Condensation Products ◽  
Acidic Compounds ◽  
Isoxazole Derivatives

The diformylation of the dinitriles 4 and diesters 7 with the Bredereck-Simchen reagent HC[N(CH3)2]2[OC(CH3)3] (1) under microwave irradiation give the bis-enamines 6 and 8 with dramatically reduced reaction times and improved yields compared to conventional heating. The condensation products formed can be easily converted to bis-pyrazole and bis-isoxazole derivatives 13 and 20, respectively. Methyl anthranilate reacts on prolonged heating with the orthoamide 21 to give ketene aminal 23 in low yield (8 %). Under microwave irradiation the same reagents lead to a mixture of 23 (14 %) and dihydropyrane 24 (28 %).

Efficient, microwave-assisted intramolecular 1,3-dipolar cycloadditions of oximes and N-methylnitrones derived from o-alkenylmethoxy-acetophenones

2005 ◽  
Vol 83 (3) ◽  
pp. 260-265 ◽  
Author(s):  
Surinderjit Singh ◽  
M PS Ishar ◽  
Gajendra Singh ◽  
Rajinder Singh
Keyword(s):  
Microwave Irradiation ◽  
Microwave Heating ◽  
Reaction Times ◽  
Solvent Free ◽  
Dipolar Cycloadditions ◽  
Microwave Assisted ◽  
Solvent Free Conditions ◽  
A Minor ◽  
Acetophenone Oxime

Contrary to literature reports, the o-allyloxy- and crotyloxy-acetophenone-oximes (2a, 2b) are transformed to nitrones, which undergo regio- and stereoselective intramolecular 1,3-dipolar cycloadditions, both on microwave heating under solvent free conditions and refluxing in toluene, to afford novel cycloadducts (5a, 5b); the oxazepine-N-oxide (3a) reported to be formed in 98% yield was obtained only as a minor product (~10%). However, o-cinnamyloxy-acetophenone-oxime (2c) under similar conditions undergoes intramolecular N-alkylation to afford nitrone (3c). The reactions carried out under microwave irradiation are cleaner, require shorter reaction times, and have higher yields. Corresponding intramolecular 1,3-dipolar cycloadditions of N-methylnitrones (B), generated in situ from o-alkenylmethoxy-acetophenones (1a–1c) and N-methylhydroxylamine under solvent-free microwave irradiation conditions, are completely regio- and stereoselective, require much shorter reaction times, and afford adducts (4a–4c) in higher yields, as compared with their thermal counterparts.Key words: cycloadditions, nitrones, oximes, o-alkenylmethoxy-acetophenones, microwave, isoxazolidines.

Study on Synthesis of Superabsorbent Using Microwave Heating and Water Absorbency

2011 ◽  
Vol 239-242 ◽  
pp. 1854-1857 ◽  
Author(s):  
Hao Ren ◽  
Yu Fen Zhang ◽  
Tai Zhong Huang ◽  
Juan Wang
Keyword(s):  
Microwave Heating ◽  
Saline Water ◽  
Three Dimensional ◽  
Reaction Times ◽  
Conventional Heating ◽  
Polymerization Temperature ◽  
Water Absorbency ◽  
Dimensional Network ◽  
Aqueous Solution Polymerization ◽  
Synthesis Experiment

The aqueous solution polymerization methods were carried out using microwave heating for the superabsorbent synthesis experiment. The differences between reaction temperatures and reaction times were compared respectively under the same conventional heating conditions. The results showed that microwave heating can generate better results: The maximum of distilled water absorbency is 711 times, and the maximum of 0.9% saline water absorbency is 86 times when the polymerization temperature is at 35 °C and the reaction time is 1.5 h. Water absorbency of the superabsorbent obtained using microwave heating is better than that of conventional heating. Analysis of FTIR and SEM showed that starch grafting with acrylic acid and acrylamide was successful, and a three-dimensional network structure was formed in superabsorbent. The causes of organic reactions accelerated using microwave heating were also discussed in this paper.

scholarly journals Microwave-Assisted Synthesis of Arylidene Acetophenones

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Sheauly Khatun ◽  
M. Z. H. Khan ◽  
Khodeza Khatun ◽  
M. A. Sattar
Keyword(s):  
Microwave Irradiation ◽  
Microwave Heating ◽  
Spectral Data ◽  
Condensation Reaction ◽  
Aromatic Aldehydes ◽  
Conventional Heating ◽  
Microwave Assisted Synthesis ◽  
Efficient Synthesis ◽  
H Nmr ◽  
Microwave Assisted

An efficient synthesis of arylidene acetophenones have been achieved by using the microwave heating in comparison to the conventional heating. In this work compound 1-phenyle-3-(4-droxyphenyle)-2-propen-1-one, 1-(4-chlorophenyle)-3-phenyle-2-propen-1-one, and 1-(4-chlorophenyle)-3-(4-hydroxyphenyle)-2-propen-1-one have been synthesized by the condensation reaction between aromatic aldehydes and substituted acetophenones under microwave irradiation. The compounds of aldehydes and acetophenones were used as benzaldehyde, parahydroxybenzaldehyde, acetophenone, and parachloroacetophenone. The result shows that the time taken for the reaction was reduced from the conventional 1-2 hours to 60–120 seconds. The yield of the compounds in the conventional heating was moderate while the highest yield of 90–98% was observed in MWI method. The structure of the compounds was characterized by their IR,1H-NMR spectral data.

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