Chitosan as an eco-friendly heterogeneous catalyst for Michael type addition reactions. A simple and efficient route to pyridones and phthalazines

Depending on their nature, nitrile activated methylene compounds add readily to β-enaminones in presence of chitosan to yield dienamides, pyridones or pyridine thiones. The dienamides, formed in this manner, can be readily converted to pyridones by stirring in refluxing acetic acid. Reaction of pyridazinones with a mixture containing benzaldehyde, malononitrile and chitosan affords phthalazines that are also produced by reaction of pyridazinone with benzylidene-malononitrile

Simple Efficient Routes for the Preparation of Pyrazoleamines and Pyrazolopyrimidines: Regioselectivity of Pyrazoleamines Reactions with Bidentate Reagents

Simple and efficient routes for the preparation of 2-amino-5-phenyl-4,5-dihydrofuran-3-carbonitrile (12), 2-oxo-5-phenyl-tetrahydrofuran-3-carbonitrile (13) and the 3,5-diaminopyrazole derivative 2h were developed. The results of the reactivity profiles of 12 and 2h are reported and the previously investigated reaction of pyrazole-3,5-diamine (2b) with acrylonitrile to yield compound (31), a N-1 acylation product, is currently justified by using X-ray crystallographic analysis. Taken together, the observation of alkenes and alkynes substitution when reacting with 3,5-diaminopyrazole derivative 2h is explained by the terminal electron withdrawing group. This pattern of substitution is attributed to involvement of sterically unhindered electrophiles primarily at the N-1 position. This work is licensed under a Creative Commons Attribution 4.0 International License

Green methodologies in organic synthesis: Microwave assisted solvent- and catalyst-free synthesis of enaminones and their conversion into 1,3,5-trisubstituted benzenes as well as 3-aroyl-6-substituted pyridines

Enaminones were obtained in good yields via condensing methyl ketones with (N,N-dimethylformamide dimethyl acetal) DMF-DMA under microwave irradiation in absence of solvent. These enaminones were readily converted into 1,3,5-trisubstituted benzenes. Reacting enaminones in presence of ammonium acetate has afforded pyridine derivatives

Studies with Arylhydrazono-3-oxopropanals:A novel route to synthesis of substituted pyrazoles, oxoalkanonitrile and glyoxalonitrile containing sulfa drug moieties

Coupling of enaminones 1 with diazonium salts gave thehydrazonopropanals 3a-h. Compound 3 react with ω-bromoacetophenone or α-chloroacetanilide to yield 5 and 8. These compounds were cyclized smoothly into 6 and 9 respectively. Reactions of 3 with phenylhydrazine gave diphenylhydrazones 10 which cyclized into arylazopyrazoles 11 in refluxing pyridine. However reaction of 3c-f with hydrazine hydrate afforded pyrazoles 12.Reactions of 3 with phenylhydrazine hydrochloride afforded 11. Finally, reactions of 3c with hydroxylamine hydrochloride afforded the aldoxime 14 that on refluxing in pyridine gave 15 not 16

Arylazoazines and arylazoazoles as interesting disperse dyes: Recent developments with emphasis on our contribution laboratory outcomes

In this review, we report a survey on the synthesis and application of arylazoazines and arylazoazoles as versatile disperse dyes. Recent reports on the synthesis of arylazonicotinates via condensing arylhydrazonals with active methylene nitriles in acetic acid in presence of ammonium acetate is surveyed. The scope and limitations of this synthetic approach which in some cases afford pyridazinones or arylazonicotinates is defined. Microwave assisted as well as ultra sound assisted synthesis of arylazopyridones as established marketed dyes is also surveyed. Conversion of these arylazopyridones into arylazothienopyridones that can de converted into arylazoisoquinoline derivatives is discussed. Synthesis of arylazopyrazoles and pyrazolopyrimidines via microwave or ultra sound is discussed. The utility of the synthesized compounds as well as antimicrobial disperse dyes and efforts to define their potentialities are also covered

Cerium (IV) ammonium nitrate-mediated reactions: Simple route to benzimidazole derivatives

AbstractThe reaction of o-phenylenediamine with aromatic aldehydes in MeOH at room temperature catalyzed by cerium (IV) ammonium nitrate (CAN) afforded either 2-aryl-1-arylmethyl-1H-benz-imidazoles and/or 2-aryl-substituted benzimidazoles

A facile synthesis of some biologically active disperse dyes derived from arylazonicotinates and their application on polyester fabrics

A series of 2-hydroxy- and 2-amino-6-substituted-5-arylazonicotinates monoazo disperse dyes 6 and 8a-d were prepared via condensation of 3-oxo-3-substituted-2-arylhydrazonals 1a-d with active methylene nitriles 2a,b. A high temperature dyeing method was employed to apply these disperse dyes for polyester fabrics. Fastness properties of the dyed samples were measured. Most of the dyed fabrics tested displayed very good fastness level to washing, perspiration and light. Finally, the biological activities of the prepared dyes against gram positive and gram negative bacteria were evaluated

Multicomponent reactions under increased pressure: on the reaction of arylhydrazonals, aromatic aldehydes and malononitrile in Q-Tube

A novel multi-component reaction between arylhydrazonals, malononitrile and aromatic aldehydes under high pressure utilizing Q-tube was carried out. The reaction of arylhydrazonal (1j) with malononitrile and aromatic aldehydes afforded the corresponding biphenyl derivatives (4). However, compound 1h reacted with malononitrile and aromatic aldehydes (7) to afford pyridazino[5,4,3-de]1,6-naphthyridine-7-carbonitrile derivatives (8). In contrast, the arylhydrazonal (1k) at the same reaction conditions afforded the corresponding pyridazinoquinazoline derivative (22). A rationalization for the difference in behavior for reaction of compounds 1h-k with malononitrile and aromatic aldehydes was postulated. Based on these findings a mechanism to account for the formation of the reaction products is suggested excluding possible initial dimerization of malononitrile as has been previously reported

Revisiting the structure and chemistry of 3(5)-Substituted Pyrazoles

Pyrazoles are known as versatile scaffolds in organic synthesis and medicinal chemistry, often used as starting materials for the preparation of more complex heterocyclic systems with relevance in the pharmaceutical field. Pyrazoles are also interesting compounds from a structural viewpoint, mainly because they exhibit tautomerism. This phenomenon may influence their reactivity, with possible impact on the synthetic strategies where pyrazoles take part, as well as on the biological activities of targets bearing a pyrazole moiety, since a change in structure translates into changes in properties. Investigations of the structure of pyrazoles that unravel the tautomeric and conformational preferences are therefore of upmost relevance. 3(5)-Aminopyrazoles are largely explored as precursors in the synthesis of condensed heterocyclic systems, namely pyrazolo[1,5-a]pyrimidines. However, the information available in the literature concerning the structure and chemistry of 3(5)-aminopyrazoles is scarce and disperse. We provide a revision of data on the present subject, based on investigations using theoretical and experimental methods, together with the applications of the compounds in synthesis. It is expected that the combined information will contribute to a deeper understanding of structure/reactivity relationships in this class of heterocycles, with a positive impact in the design of synthetic methods, where they take part.info:eu-repo/semantics/publishedVersio