Cyclization reactions

A series of chalcone analogues were synthesized using Claisen-Schmidt condensation and assayed for in vitro inhibitory activity against α-glucosidase. The synthesis involved in solvent-free reaction conditions including NaOHcatalyzed grinding or microwave irradiation in the presence of a clay-based catalyst. Hydroxychalcones and 2′-hydroxychalcones were not isolated when using grinding method, while the microwave-assisted, clay-catalyzed synthesis gave these desired products. In addition, flavanones, cyclization products from 2′-hydroxychalcones were formed in both methods.

8p dianmotminh02 03-05-2024 5 1   Download

Ebook "Polycondensation: History and new results" reports on origin and history of polycondensation chemistry beginning in the first half of the 19th century. Furthermore, history and inventors of the most important polycondensates, such as Nylons, PET or polycarbonates, are described. The classical theory of step-growth polymerizations is discussed in the light of the latest experimental and theoretical results. Particular emphasis is laid on the role of cyclization reactions.

291p tudohanhtau1006 29-03-2024 2 1   Download

Ebook "Stereoselective syntheses of tetrahydropyrans: Applications to the synthesis of (+)-Leucascandrolide A, (+)-Dactylolide and (±)-Diospongin A" describes his studies into tandem and organocatalytic oxa-conjugate addition reactions for the synthesis of complex tetrahydropyrans (THP). Readers gain insight into the new methods Lee employs for the synthesis of biologically interesting natural products including (+)-leucascandrolide A, (+)-dactylolide, and (±)diospongin A.

198p tudohanhtau1006 29-03-2024 2 1   Download

Ebook "Chemistry of 1,2,3-triazoles (Topics in Heterocyclic chemistry, Volume 40)" has been an important topic in heterocyclic chemistry since the first such heterocycles were prepared in the nineteenth century by von Pechmann (1888). Publications on triazoles have increased steadily ever since but there has recently been a remarkable additional interest due to the CuAAC (copper-catalyzed acetylene/azide cycloaddition) discovered by Meldal and Sharpless and related azide cycloaddition reactions, leading to a surge of publications and new applications for triazoles.

389p tudohanhtau1006 29-03-2024 6 1   Download

Ebook "The chemistry of zirconacycles and 2,6-diazasemibullvalenes: Synthesis, structures, reactions, and applications in the synthesis of novel N-heterocycles" introduces two strategies used to construct various types of N-heterocycles, based on the chemistry of zirconacycles and 2,6-diazasemibullvalenes. In the first part, the author presents the development of multi-component cyclization of a zirconacyclobutene-silacyclobutene fused compound, nitriles and unsaturated compounds.

182p manmanthanhla0201 26-02-2024 11 1   Download

A series of novel N -[3-(2-benzo[d]thiazol-2-yl)-4-methylthiazol-2(3H)-ylidene] substituted benzamides (2a–k) were efficiently synthesized by heterocyclization of the corresponding 1-(benzo[d]thiazol-2-yl)-3-aroylthioureas (1a–k). The cyclization was achieved by the reaction of α-bromoacteone produced in situ using bromine in dry acetone in the presence of triethylamine.

8p langthannam 29-12-2021 7 0   Download

One-pot syntheses of the value-added heterocyclic compounds 3-methylpyridine and pyridine using a renewable chemical, glycerol, were achieved in acidic medium by thermal conversion reactions. Condensation/cyclization reactions of the thermal degradation products of glycerol were investigated in situ using different ammonia and acidic moiety producing inorganic ammonium salts under pyrolysis or microwave heating conditions.

10p langthannam 29-12-2021 21 0   Download

A facile synthesis of bis-thiazoles, bis-pyrazoles, and bis-hydrazonates from the reaction of bis-hydrazonoyl dichlorides with different moieties is described. Bis-triazolothiadiazoles were synthesized via oxidative cyclization of bis-hydrazones. Structures of the final product were elucidated by elemental analyses and spectral data.

10p langthannam 29-12-2021 3 0   Download

6H-Benzo[c]chromen-6-ones serve as core structures of secondary metabolites and are of considerable pharmacological importance. Natural sources produce limited quantities, hence the need for synthetic procedures for 6H-benzo[c]chromen-6-ones, which are herein reviewed.

27p langthannam 29-12-2021 9 0   Download

The present work describes the preparation of new thiadiazoles through a simple intramolecular reaction of mono- and bis-hydrazonoyl halides with methyl hydrogen phenyl carbonimidodithioate or methyl-2-arylidene hydrazinecarbodithioate. The synthetic method involves nucleophilic substitution followed by intramolecular cyclization reactions mediated by evolution of methanethiol. The structures of the title compounds were elucidated by elemental analyses, and FTIR, MS and NMR spectra.

8p langthannam 29-12-2021 8 0   Download

An efficient, convenient, and environmentally benign procedure for the synthesis of novel benzo[a]chromeno[2,3-c]phenazine derivatives has been developed by domino four-component condensation reaction between 2-hydroxynaphthalene-1,4-dione, o−phenylenediamine, aromatic aldehydes, and naphthols or phenol in the presence of a catalytic amount of DABCO as an expedient, ecofriendly, and reusable base catalyst under microwave irradiation in EtOH/H2O (1:1).

10p tudichquannguyet 29-11-2021 13 1   Download

Aliphatic nitroalkanes with different functional groups were synthesized from the Michael addition reactions of active methylene compounds 2 and nitrovinyl arenes 1 in high yields. The synthesized Michael adducts were subjected to intramolecular cyclization to give heteroaryl substituted γ -lactams in good to high yields under mild reaction conditions.

7p tudichquannguyet 29-11-2021 8 0   Download

Pyrimidine derivatives are well known due to their remarkable pharmacological potential in various fields of science, and they are also present in some natural substances like DNA and RNA. These scaffolds manifest diversified biological activities such as antimicrobial, antiinflammatory, anti-HIV, antitubercular, antitumor, antineoplastic, and antimalarial. A pyrimidine ring is constructed when chalcones, amidines, guanidine, nitriles, isocyanates, urea, thiourea, and aminopyrazoles undergo condensation, coupling, or cyclization reactions.

38p tudichquannguyet 29-11-2021 11 1   Download

Generally, 3-amino-9-ethylcarbazole is considered a versatile compound not only for its unique electronic properties but also for its significance as a building block in synthetic, pharmaceutical, and material chemistry. The synthesis, chemical reactivity, and applications of 3-amino-9-ethylcarbazole are described in this review. The presence of the amino group at position 3 exhibits a unique reactivity with both C-2 and C-4.

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The aim of this study is to synthesize novel piperazine-containing dihydrofuran compounds (3a-n)from radical additions and cyclizations of diacyl and alkyl-acyl piperazine derivatives (1a-h) with 1,3-dicarbonyl compounds (2a-c) mediated by Mn(OAc)3 for the first time. From the reactions of 1a-c with dimedone (2a);1a, 1c, and 1d with acetylacetone (2b); and 1a with ethylacetoacetate(2c) ,the dihydrofuran-piperazine compounds 3a-c, 3d-f, and 3g were obtained in medium to high yields (31%–81%), respectively.

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In this study, nine different C-2 aroyl imidazole derivatives were synthesized in a one pot reaction with two steps, and the reduction reactions of these derivatives with NaBH4 were carried out under mild conditions. Substitution reaction of obtained imidazo methanol derivatives with chloroacetylchloride reagent and ring reaction of substitution products were investigated. It was determined that 1,4-imidazoxazinone derivative was obtained as a result of the cyclization reaction.

42p tudichquannguyet 29-11-2021 6 1   Download

4-spirocyclopropaneisoxazolidine carboxylate, 1,3-amino alcohols, lactones, cleavage of the N-O bond 1, 3 - Dipolar cycloaddition of nitrones to the double carbon – carbon bond of acceptor ring substituted methylenecyclopropanes affords thermally stable regioisomeric 4 - spirocyclopropaneisoxazolidine.

4p cothumenhmong11 10-05-2021 15 2   Download

A cyclopropyl-substituted 1,3-bis(silyl enol ether) was prepared in two steps and subsequently employed in the cyclization with oxalyl chloride to give a cyclopropyl-carbonyl substituted -alkylidenebutenolide. The cyclization of the 1,3-bis(silyl enol ether) with 1,3-dielectrophiles afforded cyclopropyl-carbonyl substituted phenols. The reactions proceeded with very good regioselectivity.

3p nguaconbaynhay11 16-04-2021 15 2   Download

In this work, an attempt to planarize 2,3,4,6- tetraarylthieno[3,2-b]thiophene based on the FeCl3 oxidative annulation was described. Thus, two cyclized 2,3,5,6-tetraarylthieno[3,2-b]thiophenes 5a and 5b were synthesized in moderate yields. NMR and HR-MS analysis indicated the annulation between only one pair of the phenyl substituents.

8p tamynhan9 02-12-2020 11 2   Download

In this work, the Fe3O4@SiO2@AMBI/Cu nanocatalyst was synthesized and used as a well-organized magnetic nanocatalyst for the click reaction. This nanocatalyst has effectively catalyzed the cyclization of terminal alkynes and sodium azide with aryl iodide/benzyl halide for the formation of 1,4-disubstituted 1,2,3-triazoles under mild reaction conditions with good to high yields in low reaction time.

10p tocectocec 25-05-2020 8 1   Download