Thiazolation of phenylthiosemicarbazone to access new thiazoles: anticancer activity and molecular docking

Aim: Novel thiazole hybrids were synthesized via thiazolation of 4-phenylthiosemicarbazone (4). Materials & methods: The anticancer activity against the NCI 60 cancer cell line panel. Results: Methyl 2-(2-((1-(naphthalen-2-yl)ethylidene)hydrazineylidene)-4-oxo-3-phenylthiazolidin-5-ylidene)acetate (6a) showed significant anticancer activity at 10 μM with a mean growth inhibition (GI) of 51.18%. It showed the highest cytotoxic activity against the ovarian cancer OVCAR-4 with an IC50 of 1.569 ± 0.06 μM. Compound 6a inhibited PI3Kα with IC50 = 0.225 ± 0.01 μM. Moreover, compound 6a revealed a decrease of Akt and mTOR phosphorylation in OVCAR-4 cells. In addition, antibacterial activity showed that compounds 11 and 12 were the most active against Staphylococcus aureus. Conclusion: Compound 6a is a promising molecule that could be a lead candidate for further studies.

Reductive Coupling of a Diazoalkane Derivative Promoted by a Potassium Aluminyl and Elimination of Dinitrogen to Generate a Reactive Aluminium Ketimide

The reaction of 9-diazo-9H-fluorene (fluN2 ) with the potassium aluminyl K[Al(NON)] ([NON]2- =[O(SiMe2 NDipp)2 ]2- , Dipp=2,6-iPr2 C6 H3 ) affords K[Al(NON)(κN1 ,N3 -{(fluN2 )2 })] (1). Structural analysis shows a near planar 1,4-di(9H-fluoren-9-ylidene)tetraazadiide ligand that chelates to the aluminium. The thermally induced elimination of dinitrogen from 1 affords the neutral aluminium ketimide complex, Al(NON)(N=flu)(THF) (2) and the 1,2-di(9H-fluoren-9-yl)diazene dianion as the potassium salt, [K2 (THF)3 ][fluN=Nflu] (3). The reaction of 2 with N,N'-diisopropylcarbodiimide (iPrN=C=NiPr) affords the aluminium guanidinate complex, Al(NON){N(iPr)C(N=CMe2 )N(CHflu)} (4), showing a rare example of reactivity at a metal ketimide ligand. Density functional theory (DFT) calculations have been used to examine the bonding in the newly formed [(fluN2 )2 ]2- ligand in 1 and the ketimide bonding in 2. The mechanism leading to the formation of 4 has also been studied using this technique.

Effect of a Substituent on the Properties of Salicylaldehyde Hydrazone Derivatives

The present study investigates the effect of the substitution of salicylaldehyde hydrazones at two selected positions, i.e., the para-position with regard to the proton-donating and proton-accepting centers forming the hydrogen bridge. A detailed analysis of structural data obtained by theoretical approaches and X-ray experiments, together with original resonance Hammett's constants, indicates that the strength of the intramolecular hydrogen bonding present in salicylaldehyde hydrazones can be selectively modulated by substitution of the parent molecular system with the chemical group of known π-electron-donating or -accepting properties. Our findings provide an insight into planning synthesis pathways for salicylaldehyde hydrazone species and predicting their result with regard to their H-bonding and related physical and chemical properties.

3 a,6 a-Diaza-1,4-Diphosphapentalenes: Synthesis and Complexation with the Organic π-Acceptor 1,2,4,5-Tetracyanobenzene

The reaction of PCl₃ with diethyl ketazine and 4-phenylcyclohexanone azine results in the formation of 1,4-dichloro-3a,6a-diaza-1,4-diphosphapentalenes which were reduced by magnesium in THF to give corresponding diazadiphosphapentalenes EtMeDDP and PhcHexDDP, containing two-coordinate phosphorus atoms. According to the CVA data, the new diazadiphosphapentalenes are strong electron donors showing oxidation peak potentials at 0.34 and 0.10 V, respectively, (vs. Ag/AgCl). Interaction of 1,2,4,5-tetracyanobenzene (TCNB) with the obtained diazadiphosphapentalenes in any stoichiometry produces sandwich complexes of the composition DDP-TCNB-DDP. Black-purple crystals of π-complexes contain infinite molecular chains with short P⋅⋅⋅P contacts between DDP molecules and short (Csp² -H⋅⋅⋅N) contacts between TCNB molecules. Calculations showed that each TCNB molecule is an acceptor of ∼0.3e from two DDP molecules. Estimation of the HOMO-LUMO gap from the onset of optical absorption give values of 1.25 eV and 1.31 eV for [(EtMeDDP)₂ (TCNB)] and [(PhcHexDDP)₂ (TCNB)] respectively.

The crystal structure of 3-(1-(2-((5-methylthiophen-2-yl)methylene)hydrazinyl)ethylidene)chroman-2,4-dione, C17H14N2O3S

C17H14N2O3S, monoclinic, P21/c (no. 14), a = 9.8966(5) Å, b = 9.4360(4) Å, c = 16.7115(7) Å, β = 92.245(4)°, V = 1559.39(12) Å3, Z = 4, R gt(F) = 0.0358, wR ref(F 2) = 0.1013, T = 170 K.

Palladium-Catalyzed Oxidant Dependent Switchable Aza-Wacker Cyclization and Oxidative Dimerization of Benzimidates

An oxidant dependent switchable palladium-catalyzed synthesis of 1,3-oxazines and benzohydrazonates (azines) from O-homoallyl benzimidates has been developed. The reaction involved aza-Wacker-type intramolecular cyclization of O-homoallyl benzimidates with Cu(OAc)2 as oxidant under Pd-catalysis to deliver 4-methylene-1,3-oxazines, whereas dimerization of O-homoallyl benzimidates with K2S2O8 as oxidant resulted remarkably in benzohydrazonates (azines). The reaction is atom economic with an easily operational procedure for divergent synthesis of important scaffolds.

Selective Formation of Unsymmetric Multidentate Azine-Based Ligands in Nickel(II) Complexes

A mixture of 2-pyridine carboxaldehyde, 4-formylimidazole (or 2-methyl-4-formylimidazole), and NiCl₂·6H₂O in a molar ratio of 2:2:1 was reacted with two equivalents of hydrazine monohydrate in methanol, followed by the addition of aqueous NH₄PF₆ solution, afforded a Ni^II complex with two unsymmetric azine-based ligands, [Ni(HL^H)₂](PF₆)₂ (1) or [Ni(HL^Me)₂](PF₆)₂ (2), in a high yield, where HL^H denotes 2-pyridylmethylidenehydrazono-(4-imidazolyl)methane and HL^Me is its 2-methyl-4-imidazolyl derivative. The spectroscopic measurements and elemental analysis confirmed the phase purity of the bulk products, and the single-crystal X-ray analysis revealed the molecular and crystal structures of the Ni^II complexes bearing an unsymmetric HL^H or HL^Me azines in a tridentate κ³N, N’, N” coordination mode. The HL^H complex with a methanol solvent, 1·MeOH, crystallizes in the orthorhombic non-centrosymmetric space group P2₁2₁2₁ with Z = 4, affording conglomerate crystals, while the HL^Me complex, 2·H₂O·Et₂O, crystallizes in the monoclinic and centrosymmetric space group P2₁/n with Z = 4. In the crystal of 2·H₂O·Et₂O, there is intermolecular hydrogen-bonding interaction between the imidazole N–H and the neighboring uncoordinated azine-N atom, forming a one-dimensional polymeric structure, but there is no obvious magnetic interaction among the intra- and interchain paramagnetic Ni^II ions.

Heterocyclization of Bis(2-chloroprop-2-en-1-yl)sulfide in Hydrazine Hydrate–KOH: Synthesis of Thiophene and Pyrrole Derivatives

The article is devoted to heterocyclization of bis(2-chloroprop-2-en-1-yl)sulfide which proceeds in hydrazine hydrate–alkali medium and leads to formation of thiophene and pyrrole derivatives: previously described 4,5,9,10-tetrahydrocycloocta[1,2-c;5,8-c’]dithiophene, as well as unknown hydrazone of 5-methylidene-3-methyldihydrothiophen-2-one and 1-amino-2-(propynylsulfanylpropenylsulfanyl)-3,5-dimethylpyrrole. Tentative mechanisms for the formation of the heterocyclic products are discussed. Obtained hydrazone of 5-methylidene-3-methyldihydrothiophen-2-one was used for the synthesis of a range of azine derivatives and in oxidation process with SeO₂. The found reactions open up expedient approaches to the formation of various hardly accessible thiophene and pyrrole compounds from 2,3-dichloropropene and elemental sulfur as starting reagents.

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

Many heterocyclic compounds can be synthetized using diaza-1,3-butadienes (DADs) as key structural precursors. Isolated and in situ diaza-1,3-butadienes, produced from their respective precursors (typically imines and hydrazones) under a variety of conditions, can both react with a wide range of substrates in many kinds of reactions. Most of these reactions discussed here include nucleophilic additions, Michael-type reactions, cycloadditions, Diels–Alder, inverse electron demand Diels–Alder, and aza-Diels–Alder reactions. This review focuses on the reports during the last 10 years employing 1,2-diaza-, 1,3-diaza-, 2,3-diaza-, and 1,4-diaza-1,3-butadienes as intermediates to synthesize heterocycles such as indole, pyrazole, 1,2,3-triazole, imidazoline, pyrimidinone, pyrazoline, -lactam, and imidazolidine, among others. Fused heterocycles, such as quinazoline, isoquinoline, and dihydroquinoxaline derivatives, are also included in the review.

Dynamic covalent chemistry with azines

Dynamic covalent chemistry is used in many applications that require both the stability of covalent bonds and the possibility to exchange building blocks. Here we present azines as a dynamic covalent functional group that combines the best characteristics of imines and acylhydrazones. We show that azines are stable in the presence of water and that dynamic combinatorial libraries of azines and aldehydes equilibrate in less than an hour.

Synthesis of cis-thiiranes as diastereoselective access to epoxide congeners via 4π-electrocyclization of thiocarbonyl ylides

Organochalcogen heterocycles are ubiquitously present and widely utilized in various fields. Among them, oxirane has been extensively studied, and all of the stereoisomeric forms are readily available. In contrast, synthetic studies on thiirane were rarely reported, and thus the useful sulfur-congener of oxirane has been difficult to access in a stereodefined form. In this research, a general stereoselective synthesis of cis-thiiranes is accomplished by taking advantage of stereospecific electrocyclization of trans-thiocarbonyl ylides, which are generated in situ from readily available E,E-aldazine N-oxides upon treatment with Lawesson's reagent. This newly developed practical method provides a variety of cis-1,2-diarylthiiranes as essentially single diastereomers in high yields under mild reaction conditions. The intermediacy of trans-thiocarbonyl yilde is confirmed by mechanistic experiments, and the excellent stereocontrol is rationalized by DFT calculation.

Azine- and imine-linked conjugated polyHIPEs through Schiff-base condensation reaction

A new alternative synthetic route to the transition-metal free π-conjugated polyHIPEs is reported, which combines the Schiff-base condensation reaction and an emulsion-templating technology.

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.

Ruthenium(ii)-catalysed 1,2-selective hydroboration of aldazines

Herein, an efficient and simple catalytic method for the selective and partial reduction of aldazines using ruthenium catalyst [Ru(p-cymene)Cl₂]₂ (1) has been accomplished. Under mild conditions, aldazines undergo the addition of pinacolborane in the presence of a ruthenium catalyst, which delivered N-boryl-N-benzyl hydrazone products. Notably, the reaction is highly selective, and results in exclusive mono-hydroboration and desymmetrization of symmetrical aldazines. Mechanistic studies indicate the involvement of in situ formed intermediate [{(η⁶-p-cymene)RuCl}2(μ-H-μ-Cl)] (1a) in this selective hydroboration.

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.

Recent advances in pincer-nickel catalyzed reactions

Organometallic catalysts have played a key role in accomplishing numerous synthetically valuable organic transformations that are either otherwise not possible or inefficient. The use of precious, sparse and toxic 4d and 5d metals are an apparent downside of several such catalytic systems despite their immense success over the last several decades. The use of complexes containing Earth-abundant, inexpensive and less hazardous 3d metals, such as nickel, as catalysts for organic transformations has been an emerging field in recent times. In particular, the versatile nature of the corresponding pincer-metal complexes, which offers great control of their reactivity via countless variations, has garnered great interest among organometallic chemists who are looking for greener and cheaper alternatives. In this context, the current review attempts to provide a glimpse of recent developments in the chemistry of pincer-nickel catalyzed reactions. Notably, there have been examples of pincer-nickel catalyzed reactions involving two electron changes via purely organometallic mechanisms that are strikingly similar to those observed with heavier Pd and Pt analogues. On the other hand, there have been distinct differences where the pincer-nickel complexes catalyze single-electron radical reactions. The applicability of pincer-nickel complexes in catalyzing cross-coupling reactions, oxidation reactions, (de)hydrogenation reactions, dehydrogenative coupling, hydrosilylation, hydroboration, C-H activation and carbon dioxide functionalization has been reviewed here from synthesis and mechanistic points of view. The flurry of global pincer-nickel related activities offer promising avenues in catalyzing synthetically valuable organic transformations.

Modified multiwall carbon nanotubes display either phytotoxic or growth promoting and stress protecting activity in Ocimum basilicum L. in a concentration-dependent manner

Carbon-based materials including multiwall carbon nanotubes (MWCNTs) have been recently implicated in a number of reports dealing with their potential use in agriculture, leading to contradictory findings. In this study, MWCNTs were successfully functionalized with carboxylic acid groups (MWCNTs-COOH) in order to increase water dispersion. Hydroponically cultured sweet basil (Ocimum basilicum L.) seedlings were subjected to four concentrations (0, 25, 50 and 100 mg L^-1) of MWCNTs-COOH under three salt stress levels (0, 50 and 100 mM NaCl). An array of agronomic, physiological, analytical and biochemical parameters were evaluated in an attempt to examine the potential use of MWCNTs in plants under optimal and abiotic stress conditions. Application of MWCNTs-COOH at optimum concentration (50 mg L^-1) could ameliorate the negative effects of salinity stress by increasing chlorophyll and carotenoids content and inducing non-enzymatic (i.e. phenolic content) and enzymatic antioxidant components (i.e. ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase (GP) activity). Furthermore, MWCNTs-COOH treatments under optimal conditions induced plant growth, while a significant increase (P ≤ 0.01) was recorded in essential oil content and compound profile. On the other hand, biochemical and epifluorescence microscopy evidence suggested that high dosage (100 mg L^-1) of MWCNTs-COOH leads to toxicity effects in plant tissue. Overall, the positive response of plants to low concentrations of MWCNTs-COOH under control and abiotic stress conditions renders them as potential novel plant growth promoting and stress protecting agents, opening up new perspectives for their use in agriculture.

ESIPT-active multi-color aggregation-induced emission features of triphenylamine–salicylaldehyde-based unsymmetrical azine family

A new family of ESIPT and AIE-active triphenylamine-appended unsymmetrical azine derivatives is reported.

Reactions of hydrazones and hydrazides with Lewis acidic boranes

The reaction of (diphenylmethylene)hydrazone or 1,4-bis-hydrazone-ylidene(phenylmethyl)benzene with Lewis acidic boranes B(2,4,6-F₃C₆H₂)₃ or B(3,4,5-F₃C₆H₂)₃ generates the Lewis acid-base adducts. Alternatively, when (9H-fluoren-9-ylidene)hydrazone is employed several products were isolated including 1,2-di(9H-fluoren-9-ylidene)hydrazone, the 2 : 1 borane adduct of NH₂-NH₂ and the 1-(diarylboraneyl)-2-(9H-fluoren-9-ylidene)hydrazone in which one ArH group has been eliminated. The benzhydrazide starting material also initially gives an adduct when reacted with Lewis acidic boranes which upon heating eliminates ArH generating a CON₂B heterocycle.

A Two-Coordinate Iron(II) Imido Complex with NHC Ligation: Synthesis, Characterization, and Its Diversified Reactivity of Nitrene Transfer and C-H Bond Activation

Iron terminal imido species are typically implicated as reaction intermediates in iron-catalyzed transformations. While a large body of work has been devoted to mid- and high-valent iron imidos, to date the chemistry of iron(II) imidos has remained largely unexplored due to the difficulty in accessing them. Herein, we present a study on the two-coordinate iron(II) imido complex [(IPr)Fe(NAr^Trip)] (3; IPr = 1,3-bis(2′,6′-diisopropylphenyl)imidazol-2-ylidene; Ar^Trip = 2,6-bis(2′,4′,6′-triisopropylphenyl)phenyl) prepared from the reaction of an iron(0) complex with the bulky azide Ar^TripN₃. Spectroscopic investigations in combination with DFT calculations established a high-spin S = 2 ground spin state for 3, consistent with its long Fe–N multiple bond of 1.715(2) Å revealed by X-ray diffraction analysis. Complex 3 exhibits unusual activity of nitrene transfer and C–H bond activation in comparison to the reported iron imido complexes. Specifically, the reactions of 3 with CH₂=CHAr^CF3, an electron-deficient alkene, and CO, a strong π acid, readily afford nitrene transfer products, Ar^CF3CH=CHNHAr^Trip and Ar^TripNCO, respectively, yet no similar reaction occurs when 3 is treated with electron-rich alkenes and PMe₃. Moreover, 3 is inert toward the weak C(sp³)–H bonds in 1,4-cyclohexadiene, THF, and toluene, whereas it can cleave the stronger C(sp)–H bond in p-trifluoromethylphenylacetylene to form an iron(II) amido alkynyl complex. Interestingly, intramolecular C(sp³)–H bond functionalization was observed by adding (p-Tol)₂CN₂ to 3. The unique reactivity of 3 is attributed to its low-coordinate nature and the high negative charge population on the imido N atom, which render its iron–imido unit nucleophilic in nature.

The two-coordinate iron(II) imido complex (IPr)Fe(NAr^Trip) (3) exhibits a high-spin ground state (S = 2) and was found to be reactive toward electron-deficient alkene, diazo compounds, terminal alkyne, et al., in which diversified reactivities of nitrene transfer, C−H bond activation, and C−N bond formation have been observed. The reactivity pattern reflects the nucleophilic nature of the imido moiety of the high-spin iron(II) complex.

Ruthenium(ii)-catalysed direct synthesis of ketazines using secondary alcohols

Direct one-pot synthesis of ketazines from secondary alcohols and hydrazine hydrate catalyzed by a ruthenium pincer complex is reported, which proceeds through O-H bond activation of secondary alcohols via amine-amide metal-ligand cooperation in the catalyst. Remarkably, liberated molecular hydrogen and water are the only byproducts.

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.

Using the Supermolecule Approach To Predict the Nonlinear Optics Potential of a Novel Asymmetric Azine

Organic molecules with electron acceptors or withdrawal substituents terminal at π-conjugated system are promising candidates to be explored as materials with high linear and nonlinear optical properties. On the basis of these features, a novel asymmetric azine ( 7E, 8E)-2-(3-methoxy-4-hydroxy-benzylidene)-1-(4-nitrobenzylidene)hydrazineC₁₅H₁₃N₃O₄ (NMZ) was synthesized. The molecular structure of NMZ was elucidated by X-ray crystallography and the supramolecular arrangement was analyzed from Hirshfeld surface methodology. An iterative electrostatic scheme using a super molecule approach, where neighboring molecules are represented by charge points, was employed to investigate optical dipole moment (μ), the linear polarization (α) and the first (β) and second (γ) hyperpolarizabilities. The NMZ crystallized in the centrosymetric space group P2₁/n and packs via combined O-H···O, C-H···O, and N···π interactions. The macroscopic property of third order χ⁽³⁾ found for the NMZ is 298.62 times greater than values reported for chalcone derivative (2 E)-1-(3-bromophenyl)-3-[4 (methylsulfanyl)phenyl]prop-2-en-1-one. The results for NMZ indicate a good nonlinear optical effect.

Crystal structures and Hirshfeld surface analysis of four 1,4-bis(methoxyphenyl)-2,3-diazabuta-1,3-dienes: comparisons of the intermolecular interactions in related compounds

The crystal structures of four azines, namely 1-3-bis(4-methoxyphenyl)-2,3-diaza-1,4-butadiene, 1, 1,3-bis(2,3-dimethoxyphenyl)-2,3-diaza-1,4-butadiene, 2, 1,3-bis(2-hydroxy-3-methoxyphenyl)-2,3-diaza-1,4-butadiene, 3, and 1,3-bis(2-hydroxy-4-methoxyphenyl)-2,3-diaza-1,4-butadiene, 4, are reported. Molecules of 3 and 4, and both independent molecules of 2, Mol A and Mol B, possess inversion centers. The central C=N–N=C units in each molecule is planar with an (E,E) conformation. The intermolecular interactions found in the four compounds are C–H···O, C–H–N, C–H---π and π---π interactions. However, there is no consistent set of intermolecular interactions for the four compounds. Compound, 1, has a two-dimensional undulating sheet structure, generated from C–H···O and C–H···N intermolecular hydrogen bonds. The only recognized intermolecular interaction in 2 is a C–H···O hydrogen bond, which results in a zig-zag chain of alternating molecules, Mol A and Mol B. While 3 forms a puckered sheet of molecules, solely via C–H···π interactions, its isomeric compound, 4, has a more elaborate three-dimensional structure generated from a combination of C–H···O hydrogen bonds, C–H···π and π···π interactions.

The findings in this study, based on both PLATON and Hirshfeld approaches, for the four representative compounds match well the reported structural findings in the literature of related compounds, which are based solely on geometric parameters.