Azine-Hydrazone Tautomerism of Guanylhydrazones: Evidence for the Preference Toward the Azine Tautomer

An NNN Pd(II) pincer complex with 1,1-diaminoazine: a versatile catalyst for acceptorless dehydrogenative coupling reactions

An azine-based, non-palindromic, neutral NNN-pincer ligand was synthesised in a single step with an yield of 85%. The palladation of the ligand, using Pd(OAc)2, was performed in acetonitrile at room temperature to obtain the pincer complex in 88% yield through a simple, cost-effective, and straightforward synthetic procedure. The structure of the complex was confirmed by 1H NMR, 13C NMR, FT-IR, and mass spectrometry. The variable temperature NMR spectra revealed the stability of the complex even at higher temperatures, a characteristic feature of pincer complexes. The generated complex proved to be a versatile catalyst for Acceptorless Dehydrogenative Coupling (ADC) to synthesize N-heterocycles: (i) 1,2-disubstituted benzimidazoles, (ii) 2-phenylquinolines, (iii) 2-phenylquinoxalines and (iv) 2-phenylquinazolinones. Since the side products of the reactions are H2O and H2 gas, the catalysis can be considered as a green catalytic process. Quantum chemical calculations indicated the participation of a possible nitrene-imide conversion process during the Metal-Ligand Cooperation (MLC) in ADC reactions.

Facile synthesis of azines by carboxylic acid esters as catalyst and facilitation of intersystem crossing (ISC) in azines by azine chromophore

Development of new organic synthetic methods fascinating the researchers which facilitating the increasing demands of the modern society, environmental friendly with high efficiency and low cost. The introduction of chromophores in an organic molecules facilitating intersystem crossing (ISC) to harvest both singlet and triplet excitons is also currently demanding field. We report a facile synthesis of symmetrical azines from carbonyl compounds and hydrazine hydrate with carboxylic acid esters as catalyst in methanol. This reaction presents a condensation of primary amino groups in hydrazine hydrate and carbonyl compounds took place simultaneously in a very short refluxing time. The prepared azines 1-10 were structurally analysed by various analytical techniques such as LC-MS1, H NMR13, C NMR, UV-Vis, FTIR and single crystal X-ray diffraction. Photoluminescence properties of prepared azines were recorded in CCl4 at 1 × 10-3 M and excitation range from 329 to 362 nm. The photoluminescence analysis results revealed that compounds 1-10 (except 8) were showed delayed fluorescence and 8 was showed fluorescence property. The photophysical properties of compounds 1-10 such as electron density and band gap energies was calculated by density function theory. This results revealed that the intra-molecular charge transfer occurs within the azines. The azine function in the azines enabling intersystem crossing hence, it is showing phosphorescence.

Tuning of (E)-(4-fluorophenyl)-1,1-diamino-2,3-diazabuta-1,3-diene nanostructures for the selective detection of imidacloprid

The present work demonstrates a facile route for synthesizing the organic nanoparticles (ONPs) and the blue fluorescent Quantum Dots (QDs) based on an organic molecule named (E)-(4-fluorophenyl)-1,1-diamino-2,3-diazabuta-1,3-diene. The synthesis process possesses advantages viz green synthesis, non-toxic degraded products, and amount of organic compound. Initially, the ONPs were prepared using the nanoprecipitation method and were screened for their recognition potential against various pesticides, however, no selectivity has been observed. This motivated us to tune the ONPs into QDs. The QDs were prepared using the hydrothermal method and a color change was observed in the QDs solution under daylight and under a UV lamp. The emission wavelength was observed at 400 nm (λexcitation = 278 nm). The synthesized QDs exhibited selective sensing potential towards imidacloprid via a quenching mechanism. A normalised decrement in the luminescence intensity of QDs was observed on raising the concentration of imidacloprid and a good linear response was noticed over a concentration varies from 1 μM to 100 μM with a regression coefficient of 0.99. The detection limit was estimated to be 4.53 nM and quantification limit was calculated to be and 13.72 nM.

Catalyst- and Additive-Free C(sp3)-H Functionalization of (Thio)barbituric Acids via C-5 Dehydrogenative Aza-Coupling Under Ambient Conditions

A one-pot room-temperature-based three-component reaction strategy has been accomplished to access a new series of bio-relevant barbituric/2-thiobarbituric acid hydrazones from the reaction between barbituric/2-thiobarbituric acids, primary aromatic amines, and tert-butyl nitrite in an acetonitrile solvent, without the aid of any catalysts/additives. The ambient reaction conditions can efficiently implement the C(sp³)-H functionalization of barbituric/2-thiobarbituric acids via C-5 dehydrogenative aza-coupling. The process does not require column chromatographic purification; pure products are obtained by simple filtration of the resulting reaction mixture, followed by washing the crude residue with distilled water. The catalyst-free ambient reaction conditions, operational simplicity, broad substrate scope and tolerance for various functional groups, no need for chromatographic purification, good to excellent yields of products within reasonable reaction times in minutes, clean reaction profile, and gram-scale synthetic applicability make this procedure attractive, green, and cost-effective.

11H-Indeno[1,2-b]quinoxalin-11-one 2-(4-ethylbenzylidene)hydrazone

11H-Indeno[1,2-b]quinoxaline derivatives present an important type of nitrogen-containing heterocyclic compound that are useful intermediate products in organic synthesis and have potential pharmaceutical applications. A new 11H-indeno[1,2-b]quinoxalin-11-one-2-(4-ethylbenzylidene)hydrazone (compound 3) was synthesized. Compound 3 is the first example of an azine derivative based on the 11H-indeno[1,2-b]quinoxaline system. The Z,E-isomerism of compound 3 was investigated by DFT calculations. Bioavailability was evaluated in silico using ADME predictions. According to the ADME results, compound 3 is potentially highly bioavailable and has potential to be used for the treatment of neuroinflammation and ischemia–reperfusion injury.

1,1-Diaminoazines as organocatalysts in phospha-Michael addition reactions

1,1-Diaminoazines can act as effective organocatalysts for the formation of phosphorus-carbon bonds between biphenylphosphine oxide and an activated alkene (Michael acceptor). These catalysts provide the P-C adducts at a faster rate and with relatively better yields in comparison to the organocatalysts employed earlier. The notable advantage is that 1,1-diaminoazines catalyse the reaction even in an aqueous medium with very good yields. Organocatalysis using 1,1-diaminoazines was also successfully carried out between dimethylphosphite and benzylidenemalononitrile under multicomponent conditions.

Iodine Catalyzed Oxidative Coupling of Diaminoazines and Amines for the Synthesis of 3,5-Disubstituted-1,2,4-Triazoles

A simple, convenient, transition metal-free one pot synthesis of 3,5-disubstituted-1,2,4-triazoles has been established. The innovation in this reaction is the use of easily available 1,1-diaminoazines as substrates. This method provides the products with wider substrate scope, at an expedited rate, and with relatively better yields in comparison to the reported methods. The reaction mechanism involves an initial intermolecular nucleophilic addition (facilitated by I₂) followed by intramolecular nucleophilic cyclization.

Synthesis and Biological Activity of Hydrazones and Derivatives: A Review

Hydrazones and their derivatives are very important compounds in medicinal chemistry due to their reported biological activity for the treatment of several diseases, like Alzheimer's, cancer, inflammation, and leishmaniasis. However, most of the investigations on hydrazones available in literature today are directed to the synthesis of these molecules with little discussion available on their biological activities. With the purpose of bringing lights into this issue, we performed a revision of the literature and wrote this review based on some of the most current research reports of hydrazones and derivatives, making it clear that the synthesis of these molecules can lead to new drug prototypes. Our goal is to encourage more studies focused on the synthesis and evaluation of new hydrazones, as a contribution to the development of potential new drugs for the treatment of various diseases.

Retromer stabilization results in neuroprotection in a model of Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a fatal disease characterized by the degeneration of upper and lower motor neurons (MNs). We find a significant reduction of the retromer complex subunit VPS35 in iPSCs-derived MNs from ALS patients, in MNs from ALS post mortem explants and in MNs from SOD1G93A mice. Being the retromer involved in trafficking of hydrolases, a pathological hallmark in ALS, we design, synthesize and characterize an array of retromer stabilizers based on bis-guanylhydrazones connected by a 1,3-phenyl ring linker. We select compound 2a as a potent and bioavailable interactor of VPS35-VPS29. Indeed, while increasing retromer stability in ALS mice, compound 2a attenuates locomotion impairment and increases MNs survival. Moreover, compound 2a increases VPS35 in iPSCs-derived MNs and shows brain bioavailability. Our results clearly suggest the retromer as a valuable druggable target in ALS.

ALS is a neurodegenerative disease characterized by loss of motor neurons. Here, the authors showed that reduced levels of the VSP35 subunit in the retromer complex is a conserved ALS feature and identified a new lead compound increasing retromer stability ameliorating the disease phenotype.

Investigations on the E/Z-isomerism of neonicotinoids

We investigate the minimum-energy path for the rotation of formal C=N double bonds in molecules with guanidine-like substructures as present in the chemical class of neonicotinoids. The transitions between the E- and Z-isomers of several neonicotinoids using scans of the torsional potential energy hypersurfaces are quantified at the DFT-level of theory. The validity of using this ansatz is checked by single-point CCSD(T) calculations for model systems like nitroguanidine. A combined approach of theory and experiment permits to unambiguously identify the relevant isomers present at ambient conditions. As an example, MP2-GIAO predictions of the NMR spectra of E- and Z-Clothianidin are experimentally confirmed by low-temperature NMR-experiments identifying for the first time the hitherto unknown Z-Isomer of Clothianidin.

Fabrication of a Hydrazone-Based Al(III)-Selective "Turn-On" Fluorescent Chemosensor and Ensuing Potential Recognition of Picric Acid

A hydrazone-based N'1,N'3-bis((E)-4-(diethylamino)-2 -hydroxybenzylidene)isophthalohydrazide (NDHIPH), has been synthesized, characterized, and assessed for its highly selective and sensitive (limit of detection, 2.53 nM) response toward Al(III) via fluorescence enhancement in 95% aqueous medium. All experimental results of analytical studies are in good consonance with the theoretical studies performed. Further, this NDHIPH-Al(III) ensemble is used for selective and sensitive (12.15 nM) detection of explosive picric acid (PA) via fluorescence quenching. This reversible behavior of NDHIPH toward Al(III) and PA is used for the creation of a molecular logic gate.

Azines: synthesis, structure, electronic structure and their applications

Azines (2,3-diaza-1,3-butadienes): structure, electronic structure, tautomerism, and their applications in organic synthesis, medicinal chemistry and materials chemistry.

An unprecedented intramolecular to intermolecular mechanistic switch in 1,1-diaminoazines leading to differential product formation during the I2-induced tandem oxidative transformation

Intermolecular cyclization of 1,1-diaminoazine.

Electronic and ligating properties of carbocyclic carbenes: A theoretical investigation

Carbocyclic carbenes (CCCs) are a class of nucleophilic carbenes which are very similar to N-heterocyclic carbenes (NHCs) in terms of their reactivity, but they do not contain a stabilizing heteroatom in their cyclic ring system. In this study, 17 representative known CCCs and 34 newly designed CCCs are evaluated using quantum chemical methods, and the results are compared in terms of their stability, nucleophilicity, and proton affinity (PA) parameters. The results are divided on the basis of ring size of the known and reported CCCs. The stability, nucleophilicity, PA, complexation energy, and bond strength-related parameters were estimated using M06/6-311++G(d,p) method. The results indicated that the CCCs known in the literature are strong σ-electron donating species and have considerable π-accepting properties. This study led to the design and identification of a few new CCCs with dimethylamine and diaminomethynyl substituents which can be singlet stable and are substantially nucleophilic. © 2018 Wiley Periodicals, Inc.

Interactions of Schiff base compounds and their coordination complexes with the drug cisplatin

There is a complex interplay between the structural and other physicochemical properties of new compounds and the molecules in living organisms.

Sulfonamide vs. sulfonimide: tautomerism and electronic structure analysis of N-heterocyclic arenesulfonamides

Experimental and computational studies suggest a preference toward the sulfonimide tautomer in N-heterocyclic arenesulfonamide.