scholarly journals TMSOTf-catalyzed synthesis of trisubstituted imidazoles using hexamethyldisilazane as a nitrogen source under neat and microwave irradiation conditions

RSC Advances ◽  
2021 ◽  
Vol 11 (45) ◽  
pp. 28061-28071
Author(s):  
Kesatebrhan Haile Asressu ◽  
Chieh-Kai Chan ◽  
Cheng-Chung Wang
Keyword(s):  
Microwave Irradiation ◽  
Nitrogen Source ◽  
Microwave Heating ◽  
Solvent Free ◽  
Solvent Free Conditions

Trisubstituted imidazoles are synthesized efficiently from the readily available 1,2-diketones and aldehydes using hexamethyldisilazane as a new and stable nitrogen source under TMSOTf-catalysis system, microwave heating and solvent-free conditions.

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.

scholarly journals Solvent-Free C-3 Coupling of Azaindoles with Cyclic Imines

Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3578 ◽  
Author(s):  
Khadija Belasri ◽  
Ferenc Fülöp ◽  
István Szatmári
Keyword(s):  
Microwave Irradiation ◽  
Microwave Heating ◽  
Aromatic Compounds ◽  
Acid Catalyst ◽  
Solvent Free ◽  
Direct Coupling ◽  
Pka Values ◽  
Toluenesulfonic Acid ◽  
Solvent Free Conditions

By direct coupling 7-azaindole and cyclic imines, such as 3,4-dihydroisoquinoline, 6,7-dihydrothieno[3,2-c]pyridine, 3,4-dihydro-β-carboline, and 4,5-dihydro-3H-benz[c]azepine, new 3-substituted 7-azaindole derivatives have been synthesized. The reaction was extended to 4-azaindoles and 6-azaindoles, as electron-rich aromatic compounds. The lowest reactivity was observed in the case of C-3 substitution of 5-azaindole. In this case, the aza-Friedel-Crafts reaction took place by using 10 mol % of p-toluenesulfonic acid (p-TSA) as the catalyst. The role of the acid catalyst can be explained by the different pKa values of the azaindoles. All reactions were performed in solvent-free conditions by using both classical heating and microwave irradiation. In all cases, microwave heating proved to be more convenient to synthesize new C-3-substituted azaindole derivatives.

scholarly journals Tandem Fries Reaction–Conjugate Addition under Microwave Irradiation in Dry Media; One-pot Synthesis of Flavanones

1999 ◽  
Vol 23 (9) ◽  
pp. 574-575
Author(s):  
Firouz Matloubi Moghaddam ◽  
Mohammad Ghaffarzadeh ◽  
Seyed Hossein Abdi-Oskoui
Keyword(s):  
Microwave Irradiation ◽  
Silica Gel ◽  
Conjugate Addition ◽  
Solvent Free ◽  
Naphthalene Derivatives ◽  
One Pot ◽  
Fries Rearrangement ◽  
One Pot Synthesis ◽  
Solvent Free Conditions ◽  
Fries Reaction

An AICl3–ZnCl2 mixture supported on silica gel is found to be an efficient medium for the Fries rearrangement of acyloxybenzene or naphthalene derivatives in solvent-free conditions under microwave irradiation.

Microwave-assisted synthesis of quinolones and 4H-1,4-benzo thiazine 1,1-dioxides

2005 ◽  
Vol 2005 (1) ◽  
pp. 27-28 ◽  
Author(s):  
Jaime Charris ◽  
Arthur Barazarte ◽  
José Domínguez ◽  
Neira Gamboa
Keyword(s):  
Microwave Irradiation ◽  
Rapid Method ◽  
Solvent Free ◽  
Microwave Assisted Synthesis ◽  
Microwave Assisted ◽  
Solvent Free Conditions

A rapid method for the preparation of N-aryl-2-methylthio-4-oxo-1,4-dihydro quinoline-3-carbonitriles (2a–e) and N-aryl-3-methylthio-4H-1,4-benzothiazine-2-carbonitrile 1,1-dioxides (2f–o) is reported. The cyclization is accelerated by microwave irradiation under solvent free conditions in the presence of K2CO3.

Synthesis of novel amide molecular tweezers under solvent-free conditions using microwave irradiation

2011 ◽  
Vol 35 (10) ◽  
pp. 587-591 ◽  
Author(s):  
Bitao Zeng ◽  
Lijun Zhou ◽  
Xiangbiao Li ◽  
Xianming Zhao ◽  
Zhigang Zhao ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Solvent Free ◽  
Molecular Tweezers ◽  
Solvent Free Conditions
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