scholarly journals Syntheses of 3,4- and 1,4-dihydroquinazolines from 2-aminobenzylamine

2017 ◽  
Vol 13 ◽  
pp. 1470-1477 ◽  
Author(s):  
Jimena E Díaz ◽  
Silvia Ranieri ◽  
Nadia Gruber ◽  
Liliana R Orelli
Keyword(s):  
Reaction Times ◽  
Ring Closure ◽  
Cesium Carbonate ◽  
Amino Groups ◽  
Microwave Assisted ◽  
Common Precursor ◽  
Alkylation Reactions

A straightforward strategy for the synthesis of dihydroquinazolines is presented, which allows for the preparation of 3,4- and 1,4-dihydroquinazolines with different substitution patterns from 2-aminobenzylamine (2-ABA) as common precursor. The required functionalization of both amino groups present in 2-ABA was achieved by different routes involving selective N-acylation and cesium carbonate-mediated N-alkylation reactions, avoiding protection/deprotection steps. The heterocycles were efficiently synthesized in short reaction times by microwave-assisted ring closure of the corresponding aminoamides promoted by ethyl polyphosphate (PPE).

scholarly journals Microwave-assisted cyclizations promoted by polyphosphoric acid esters: a general method for 1-aryl-2-iminoazacycloalkanes

2016 ◽  
Vol 12 ◽  
pp. 2026-2031 ◽  
Author(s):  
Jimena E Díaz ◽  
María C Mollo ◽  
Liliana R Orelli
Keyword(s):  
Polyphosphoric Acid ◽  
General Procedure ◽  
Reaction Times ◽  
Ring Closure ◽  
Heterocyclic Synthesis ◽  
Microwave Assisted ◽  
Solvent Free Conditions ◽  
High Yields ◽  
Acid Esters ◽  
General Method

The first general procedure for the synthesis of 5 to 7-membered 1-aryl-2-iminoazacycloalkanes is presented, by microwave-assisted ring closure of ω-arylaminonitriles promoted by polyphosphoric acid (PPA) esters. 1-Aryl-2-iminopyrrolidines were easily prepared from the acyclic precursors employing a chloroformic solution of ethyl polyphosphate (PPE). The use of trimethylsilyl polyphosphate (PPSE) in solvent-free conditions allowed for the synthesis of 1-aryl-2-iminopiperidines and hitherto unreported 1-aryl-2-iminoazepanes. The cyclization reaction involves good to high yields and short reaction times, and represents a novel application of PPA esters in heterocyclic synthesis.

scholarly journals Microwave-assisted synthesis of 2-substituted 4,5,6,7-tetrahydro-1,3-thiazepines from 4-aminobutanol

2020 ◽  
Vol 16 ◽  
pp. 32-38
Author(s):  
María C Mollo ◽  
Natalia B Kilimciler ◽  
Juan A Bisceglia ◽  
Liliana R Orelli
Keyword(s):  
General Procedure ◽  
Reaction Times ◽  
Solvent Free ◽  
Ring Closure ◽  
Microwave Assisted Synthesis ◽  
Microwave Assisted ◽  
Solvent Free Conditions

A general procedure for the synthesis of 2-substituted tetrahydro-1,3-thiazepines by MW-assisted cyclization of 4-thioamidobutanols is presented. The acyclic precursors were prepared in high overall yields by an expeditious three-step diacylation/thionation/deprotection sequence from 4-aminobutanol. Microwave-assisted ring closure of 4-thioamido alcohols promoted by trimethylsilyl polyphosphate (PPSE) in solvent-free conditions allowed for the synthesis of several hitherto unreported seven-membered iminothioethers bearing 2-aryl, alkenyl, aralkyl and alkyl substituents. The cyclodehydration reaction is likely to involve an SN2-type displacement and affords good to excellent yields of the desired heterocycles in very short reaction times.

scholarly journals Microwave-assisted Synthesis of 2-Substituted 4,5,6,7-Tetrahydro-1,3-thiazepines from 4-Aminobutanol

2019 ◽  
Author(s):  
María C Mollo ◽  
Natalia B Kilimciler ◽  
Juan A Bisceglia ◽  
Liliana R Orelli
Keyword(s):  
General Procedure ◽  
Reaction Times ◽  
Solvent Free ◽  
Ring Closure ◽  
Microwave Assisted Synthesis ◽  
Microwave Assisted ◽  
Solvent Free Conditions

A general procedure for the synthesis of 2-substituted tetrahydro-1,3-thiazepines is presented, by MW-assisted cyclization of 4-thioamidobutanols. The acyclic precursors were prepared in high overall yields by an expeditious three step diacylation/thionation/deprotection sequence from 4-aminobutanol. Microwave assisted ring closure of 4-thioamidoalcohols promoted by trimethylsilyl polyphosphate (PPSE) in solvent-free conditions allowed for the synthesis of several hitherto unreported seven-membered iminothioethers bearing 2-aryl, alkenyl, aralkyl and alkyl substituents. The cyclodehydration reaction is likely to involve a SN2-type displacement and affords good to excellent yields of the desired heterocycles in very short reaction times.

Microwave-Assisted Synthesis of 2-Substituted 2-Thiazolines and 5,6-Dihydro-4H-1,3-thiazines

Synthesis ◽  
2020 ◽  
Vol 52 (11) ◽  
pp. 1666-1679
Author(s):  
Liliana R. Orelli ◽  
María C. Mollo ◽  
Juan A. Bisceglia ◽  
Natalia B. Kilimciler ◽  
Michele Mancinelli
Keyword(s):  
Reaction Times ◽  
Ring Closure ◽  
Cyclization Reaction ◽  
Microwave Assisted Synthesis ◽  
Metal Free ◽  
Microwave Assisted ◽  
Whole Process ◽  
High Yields ◽  
General Method

An efficient and general method for the synthesis of 2-substituted thiazolines and 5,6-dihydro-4H-1,3-thiazines is developed via microwave-assisted ring closure of ω-thioamidoalcohols promoted by ethyl polyphosphate (PPE). The cyclization reaction involves an SN2-type mechanism and features the advantages of very short reaction times, high yields and a predictable stereochemical outcome. The acyclic precursors are prepared in high overall yields by an improved diacylation–thionation–saponification sequence from commercially available ω-amino­alcohols. The whole process is metal-free and operationally simple.

Microwave-Assisted Decarbonylation of Biomass-Derived Aldehydes Using Pd-Doped Hydrotalcites

2019 ◽  
Author(s):  
Nan An ◽  
Diana Ainembabazi ◽  
Kavya Samudrala ◽  
Christopher Reid ◽  
Kare Wilson ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Reaction Times ◽  
Inverse Correlation ◽  
Mulliken Charge ◽  
Metal Leaching ◽  
Carbonyl Carbon ◽  
Mild Conditions ◽  
Microwave Assisted ◽  
Biomass Processing ◽  
Alcohol Dehydrogenation

<p>Here we report the synthesis, characterization and activity of tunable Pd-doped hydrotalcites (Pd-HTs) for the decarbonylation of furfural, hydroxymethylfurfural (HMF), aromatic and aliphatic aldehydes under microwave conditions. The decarbonylation activity reported is a notable improvement over prior heterogeneous catalysts for this process. Furfural decarbonylation is optimized in a benign solvent compatible with biomass processing - ethanol, under relatively mild conditions and short reaction times. HMF selectively affords excellent yields of furfuryl alcohol with no humin formation, but longer reaction can also afford furan via tandem alcohol dehydrogenation and decarbonylation. Yields of substituted benzaldehydes are related to calculated Mulliken charge of the carbonyl carbon. The activity and selectivity differences can be traced to loading-dependent differences in Pd speciation on the catalysts. Poisoning studies show inverse correlation between Pd loading and metal leaching: Pd-HTs with lowest Pd loading, which consist of highly dispersed and oxidized Pd species, operate heterogeneously with negligible metal leaching. Recycling experiments are consistent with this trend, offering potential for further optimization to improve robustness.</p>

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.

scholarly journals Microwave-Assisted Asinger Synthesis of Thiazolines

2020 ◽  
Vol 3 (1) ◽  
pp. 27
Author(s):  
Raúl Eduardo Gordillo-Cruz ◽  
Liliana Gonzalez-Reyes ◽  
Milton Coporo-Reyes ◽  
Nieves Zavala-Segovia ◽  
Bernardo A. Frontana-Uribe ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Reaction Times ◽  
Reaction Conditions ◽  
Microwave Assisted

An array of 2,4-disubstituted thiazolines was obtained through Asinger reaction approach from the straightforward treatment of diverse aldehydes/ketones with 1-mercaptopropan-2-one, in the presence of NH3 assisted by microwave irradiation, displaying similar and sometimes higher yields, as well as shorter reaction times that traditional Asinger reaction conditions at room and lower temperatures.

scholarly journals Silica Supported Acids (SiO2-HClO4, SiO2-KHSO4) as Eco-friendly Reusable Catalysts for Bromination of Aromatic and Heteroaromatic Compoundsusing Kbr Under Solvothermal and Solvent-free Conditions

2021 ◽  
Author(s):  
Vijayshekar pulusu ◽  
Chinna Rajanna Rajanna Kamatala ◽  
Anil Kumar Mardhanpally ◽  
Hemanth Sriram Yel ◽  
Yaku Guguloth ◽  
...  
Keyword(s):  
Aromatic Compounds ◽  
Reaction Times ◽  
Solvent Free ◽  
Microwave Assisted ◽  
Rate Acceleration ◽  
Solvent Free Conditions ◽  
Ultrasonic Assisted

Abstract Silica supported nanogreenacids like Si-KHSO4, and Si-HClO4are explored as reusable catalysts for bromination of aromatic and hetero aromatic compounds using KBr under solvothermal, and solvent-free conditions. Reaction times reduced from Reacions under conventional solvothermal protocols conditions required (4 – 6) hours, while ultrasonic assisted reactions only (9 – 12) minutes for completion. But, solvent-free microwave assisted reactions required only (1-5) minutes exhibiting striking rate acceleration compared to the solvothermal and ultrasonic assisted protocols All the reaction protocols afforded fairly good yields of brominated products, which are comparable with existing protocols.

Microwave-assisted synthesis of zinc 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin and zinc 5-(4-carboxyphenyl)-10,15,20-triphenylchlorin

2015 ◽  
Vol 19 (04) ◽  
pp. 595-600 ◽  
Author(s):  
Rima Chouikrat ◽  
Aymeric Champion ◽  
Régis Vanderesse ◽  
Céline Frochot ◽  
Albert Moussaron
Keyword(s):  
Reaction Times ◽  
Microwave Assisted Synthesis ◽  
Spectroscopic Techniques ◽  
H Nmr ◽  
Microwave Assisted ◽  
Experimental Protocols ◽  
Time Of Reaction

The microwave-assisted synthesis of zinc 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin and zinc 5-(4-carboxyphenyl)-10,15,20-triphenylchlrorin are described and compared to classic conditions of synthesis in terms of time of reaction and yields obtained. The new experimental protocols are easy to implement required small amounts of reagents and solvents and lead to short reaction times. All compounds have been characterized by 1 H NMR, MS and spectroscopic techniques.

Versatile synthesis of functionalised dibenzothiophenes via Suzuki coupling and microwave-assisted ring closure

2011 ◽  
Vol 9 (17) ◽  
pp. 6066 ◽  
Author(s):  
Sonsoles Rodriguez-Aristegui ◽  
Kate M. Clapham ◽  
Lauren Barrett ◽  
Céline Cano ◽  
Marine Desage-El Murr ◽  
...  
Keyword(s):  
Suzuki Coupling ◽  
Ring Closure ◽  
Microwave Assisted
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