Organic Synthesis Using Microwaves and Supported Reagents

Varma, Rajender S.; Baig, R. B. Nasir

doi:10.1002/9783527651313.ch10

Cited by 5 publications

(3 citation statements)

References 276 publications

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“…The laboratory scale use of such solvent-free and even catalyst-free tactics is not unusual, but the lack of understanding of mass- and heat-transfer processes in the absence of a medium has precluded it large-scale adaptation …”

Section: Alternate Energy Input: Microwave Heating In Chemical Synthesismentioning

confidence: 99%

Greener and Sustainable Trends in Synthesis of Organics and Nanomaterials

Varma

2016

ACS Sustainable Chem. Eng.

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248

127

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Trends in greener and sustainable process development during the past 25 years are abridged involving the use of alternate energy inputs (mechanochemistry, ultrasound- or microwave irradiation), photochemistry, and greener reaction media as applied to synthesis of organics and nanomaterials. In the organic synthesis arena, examples comprise assembly of heterocyclic compounds, coupling and a variety of other name reactions catalyzed by basic water or recyclable magnetic nanocatalysts. Generation of nanoparticles benefits from the biomimetic approaches where vitamins, sugars, and plant polyphenols, including agricultural waste residues, can serve as reducing and capping agents. Metal nanocatalysts (Pd, Au, Ag, Ni, Ru, Ce, Cu, etc.) immobilized on biodegradable supports such as cellulose and chitosan, or on recyclable magnetic ferrites via ligands, namely dopamine or glutathione, are receiving special attention. These strategic approaches attempt to address most of the Green Chemistry Principles while producing functional chemicals with utmost level of waste minimization.

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Section: Alternate Energy Input: Microwave Heating In Chemical Synthesismentioning

confidence: 99%

Greener and Sustainable Trends in Synthesis of Organics and Nanomaterials

Varma

2016

ACS Sustainable Chem. Eng.

Self Cite

248

127

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“…Yields in toluene or xylene were typically around 90% ( Table 1 , entries 25 and 26). Although most reported microwave-promoted organic reactions on solid supports are performed without additional solvent [ 46 – 47 ], the combination of a nonpolar solvent with a polar heterogeneous catalyst can be effective as a consequence of the solid selectively absorbing the microwave energy and facilitating reaction at its surface, while the nonpolar solvent absorbs relatively little microwave energy and remains at a milder temperature.…”

Section: Resultsmentioning

confidence: 99%

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

Klintworth¹,

Morgans²,

Scalzullo³

et al. 2021

Beilstein J. Org. Chem.

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A wide range of N-(ethoxycarbonylmethyl)enaminones, prepared by the Eschenmoser sulfide contraction between N-(ethoxycarbonylmethyl)pyrrolidine-2-thione and various bromomethyl aryl and heteroaryl ketones, underwent cyclization in the presence of silica gel to give ethyl 6-(hetero)aryl-2,3-dihydro-1H-pyrrolizine-5-carboxylates within minutes upon microwave heating in xylene at 150 °C. Instead of functioning as a nucleophile, the enaminone acted as an electrophile at its carbonyl group during the cyclization. Yields of the bicyclic products were generally above 75%. The analogous microwave-assisted reaction to produce ethyl 2-aryl-5,6,7,8-tetrahydroindolizine-3-carboxylates from (E)-ethyl 2-[2-(2-oxo-2-arylethylidene)piperidin-1-yl]acetates failed in nonpolar solvents, but occurred in ethanol at lower temperature and microwave power, although requiring much longer time. A possible mechanism for the cyclization is presented, and further functionalization of the newly created pyrrole ring in the dihydropyrrolizine core is described.

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“…The use of MW irradiation techniques for the acceleration of organic reactions had a profound impact on these heterogeneous reactions since the appearance of initial reports on the application of microwaves for chemical synthesis in polar solvents [16,17]. The approach has now matured into a useful technique for a variety of applications in organic synthesis and functional group transformations, as is testified by a large number of books [18,19] and review articles on this theme [2][3][4][5][20][21][22][23].…”

Section: Reactions Under Solvent-free Conditions (With or Without Anymentioning

confidence: 99%