Cooperative Metal–Ligand Assisted E/Z Isomerization and Cyano Activation at CuII and CoII Complexes of Arylhydrazones of Active Methylene Nitriles

Synthesis of Chroman-2,4-diones via Ring-Opening/Ring-Closing Reaction Involving Palladium-Catalyzed Intramolecular Aryloxycarbonylation

Palladium-catalyzed aminocarbonylation of 3-iodochromone was studied in the presence of primary and secondary amines using atmospheric pressure of carbon monoxide as a carbonyl source. This procedure successfully provided a library of chromone-3-carboxamides and 3-substituted chroman-2,4-diones in 40 to 92% isolated yields. The reaction proceeded via highly chemoselective aminocarbonylation (up to 100%) in the presence of secondary amines by using monodentate or bidentate phosphine ligands. The tendency of 3-iodochromone substrate to undergo ANRORC rearrangement with N-nucleophiles was crucial to shift the reaction toward an unprecedented chemoselective carbonylative transformation, where a late-stage carbonyl insertion is favored concomitantly to the last ring-closure step. The proposed aza-Michael addition/ring-opening/intramolecular aryloxycarbonylation sequence showed compatibility, uniquely, to primary amines when XantPhos was used as a ligand. The solid-state structures of chromone-3-carboxamide (2a) and chroman-2,4-dione (3s) were undoubtedly established by single-crystal XRD analysis. A catalytic cycle was proposed to rationalize the formation of the two types of carbonylated compounds.

The Formation of a Unique 2D Isonicotinate Polymer Driven by Cu(II) Aerobic Oxidation

The isolation and structural characterization of a unique Cu(II) isonicotinate (ina) material with 4-acetylpyridine (4-acpy) is provided. The formation of [Cu(ina)₂(4-acpy)]_n (1) is triggered by the Cu(II) aerobic oxidation of 4-acpy using O₂. This gradual formation of ina led to its restrained incorporation and hindered the full displacement of 4-acpy. As a result, 1 is the first example of a 2D layer assembled by an ina ligand capped by a monodentate pyridine ligand. The Cu(II)-mediated aerobic oxidation with O₂ was previously demonstrated for aryl methyl ketones, but we extend the applicability of this methodology to heteroaromatic rings, which has not been tested so far. The formation of ina has been identified by ¹H NMR, thus demonstrating the feasible but strained formation of ina from 4-acpy in the mild conditions from which 1 was obtained.

Structural topologies involving energetically significant antiparallel π-stacking and unconventional N(nitrile)⋯π(fumarate) contacts in dinuclear Zn(ii) and polymeric Mn(ii) compounds: antiproliferative evaluation and theoretical studies

Anticancer activities considering cell viability, apoptosis and molecular docking have been explored in dinuclear Zn(ii) and polymeric Mn(ii) compounds involving energetically significant unconventional N(nitrile)⋯π(fum) contacts.

In situ transformation of a tridentate to a tetradentate unsymmetric Schiff base ligand via deaminative coupling in Ni(ii) complexes: crystal structures, magnetic properties and catecholase activity study

An N₂O donor reduced Schiff base in presence of Ni(ClO₄)₂·6H₂O and SCN⁻ transforms into N₂O₂ donor ligand via deaminative coupling. Metal complexes 1 and 3 exhibit catecholase like activity and antiferromagnetic coupling between the Ni(ii) ions.

Role of substituents on resonance assisted hydrogen bonding vs. intermolecular hydrogen bonding

Resonance assisted hydrogen bond (RAHB) ring can be weakened/opened by a strong electron-donor (ED) group.

A New 3-D Open-Framework Zinc Borovanadate with Catalytic Potentials in α-Phenethyl Alcohol Oxidation

A novel 3-D open-framework zinc borovanadate [Zn₆(en)₃][(VIVO)₆(VVO)₆O₆(B18O36(OH)₆)·(H₂O)]₂·14H₂O (1, en = ethylenediamine) was hydrothermally obtained and structurally characterized. The framework was built from [V12B18O54(OH)₆(H₂O)]10- polyanion clusters bridged by Zn(en) complex fragments. The compound not only possessed a three-dimensional open-framework structure with unique plane-shaped channels, but also exhibited excellent catalytic activities for the oxidation of α-phenethyl alcohol.

Crystal structure and Hirshfeld surface analysis of (E)-1-[2,2-di-chloro-1-(4-nitro-phen-yl)ethen-yl]-2-(4-fluoro-phen-yl)diazene

In the title compound, C14H8Cl2FN3O2, the 4-fluoro-phenyl ring and the nitro-substituted benzene ring form a dihedral angle of 63.29 (8)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds into chains running parallel to the c axis. The crystal packing is further stabilized by C-Cl⋯π, C-F⋯π and N-O⋯π inter-actions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯O/O⋯H (15.5%), H⋯H (15.3%), Cl⋯H/H⋯Cl (13.8%), C⋯H/H⋯C (9.5%) and F⋯H/H⋯F (8.2%) inter-actions.

Arylhydrazone ligands as Cu-protectors and -catalysis promoters in the azide-alkyne cycloaddition reaction

A series of water soluble copper(ii) complexes, [Cu(κO¹O²N-H₂L¹)(H₂O)₂]·2H₂O (2), [Cu(κO-H₃L¹)₂(H₂O)₄] (3), [Cu(κO-H₄L²)₂(H₂O)₄] (5) and [Cu(H₂O)₆]·2H₂L³·2(CH₃)₂NCHO (7), were prepared by the reaction of Cu(NO₃)₂·3H₂O with sodium (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)benzenesulfonate, [Na(μ₄-1:2κO¹,2κO²,3κO³,4κO⁴-H₃L¹)]_n (1; for 2 and 3), sodium (Z)-3-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)-4-hydroxybenzene-sulfonate, [Na(μ-1κO¹,2κO²-H₄L²)]₂ (4; for 5) or sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl)naphthalene-1-sulfonate, [Na(μ-1κO¹O²,2κO³-H₂L³)(CH₃OH)₂]₂ (6; for 7). Compounds 1-7 were fully characterized, also by single-crystal X-ray diffraction analysis, and applied as homogeneous catalysts for the azide-alkyne cycloaddition (AAC) reaction to afford 1,4-disubstituted 1,2,3-triazoles. A structure-catalytic activity relationship has been recognized for the first time on the basis of the occurrence of resonance- and charge-assisted hydrogen bond interactions (RAHB and CAHB), in charge and ligand binding modes, enabling the catalytic activity of the compounds to be ordered as follows: Cu(NO₃)₂≪7 (complex salt with RAHB and CAHB) < 3 (with RAHB and CAHB) < 5 (with RAHB) < 2 (neither RAHB nor CAHB). Complex 2, without such non-covalent interactions, was found to be the most efficient catalyst for the AAC reaction, affording up to 98% product yield after being placed for 15 min, at 125 °C, in a water/acetonitrile mixture under low power (10 W) MW irradiation.

Catalytic Activity of Polynuclear vs. Dinuclear Aroylhydrazone Cu(II) Complexes in Microwave-Assisted Oxidation of Neat Aliphatic and Aromatic Hydrocarbons

One-dimensional (1D) polynuclear Cu(II) complex (1) derived from (5-bromo-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H₂L) is synthesized and characterized by elemental analysis, IR spectroscopy, ESI-MS, and single crystal X-ray crystallography. Its catalytic performance towards the solvent-free microwave-assisted peroxidative oxidation of aliphatic and aromatic hydrocarbons under mild conditions is compared with that of dinuclear Cu(II) complexes (2 and 3) of the same ligand, previously reported as antiproliferative agents. Polymer 1 exhibits the highest activity, either for the oxidation of cyclohexane (leading to overall yields, based on the alkane, of up to 39% of cyclohexanol and cyclohexanone) or towards the oxidation of toluene (selectively affording benzaldehyde up to a 44% yield), after 2 or 2.5 h of irradiation at 80 or 50 °C, respectively.

Gold Nanotriangles as Selective Catalysts for Cyclohexanol and Cyclohexanone Production

The search for sustainable catalytic oxidation processes remains a challenge. One process of utmost industrial and economic importance is the selective oxidation of cyclohexane, in the route of nylon-6,6 production, which requires urgent improvement. Herein, Au nanotriangles (Au NTs) were prepared following a three-step (seed preparation, growth and shaping) procedure and applied, for the first time, as catalysts for the selective oxidation of neat cyclohexane to ketone and alcohol (KA) oil (cyclohexanol and cyclohexanone mixture). The Au NTs successfully yield KA oil (up to 14%) under mild conditions (50 °C), using an alternative energy source (microwave irradiation) as reaction promotor.

Copper(II) Complexes of Arylhydrazone of 1H-Indene-1,3(2H)-dione as Catalysts for the Oxidation of Cyclohexane in Ionic Liquids

The copper(II) complexes [CuL(H2O)2]∙H2O (1) and [CuL(dea)] (2) [L = 2-(2-(1,3-dioxo-1H-inden-2(3H)-ylidene)hydrazinyl)benzenesulfonate, dea = diethanolamine] were applied as catalysts in the peroxidative (with tert-butyl-hydroperoxide or hydrogen peroxide) conversion of cyclohexane to cyclohexanol and cyclohexanone, either in acetonitrile or in any of the ionic liquids [bmim][NTf2] and [hmim][NTf2] [bmim = 1-butyl-3-methylimidazolium, hmim = 1-hexyl-3-methylimidazolium, NTf2 = bis(trifluoromethanesulfonyl) imide]. Tert-butyl-hydroperoxide led to better product yields, as compared to H2O2, with a selectivity directed towards cyclohexanone. The ILs showed a better performance than the conventional solvent for the copper complex 1. No catalytic activity was observed for 2 in the presence of an IL.

Crystal structure of dimethyl (3aS,6R,6aS,7S)-1H,3H,6H,7H-3a,6:7,9a-diepoxybenzo[de]isochromene-3a 1,6a-dicarboxylate, C16H16O7

C16H16O7, monoclinic, P21/n (no. 14), a = 12.830(3) Å, b = 8.1101(16) Å, c = 14.900(3) Å, β = 114.88(3)°, V = 1406.5(6) Å3, Z = 4, R gt(F) = 0.0578, wR ref(F 2) = 0.1799, T = 100(2) K.

Crystal structure and Hirshfeld surface analysis of ethane-1,2-diaminium 3-[2-(1,3-dioxo-1,3-di-phenyl-propan-2-yl-idene)hydrazin-yl]-5-nitro-2-oxido-benzene-sulfonate dihydrate

In the anion of the title hydrated salt, C2H10N22+·C21H13N3O8S2-·2H2O, the planes of the phenyl rings and the benzene ring of the 5-nitro-2-oxido-benzene-sulfonate group are inclined to one another by 44.42 (11), 56.87 (11) and 77.70 (12)°. In the crystal, the anions are linked to the cations and the water mol-ecules by N-H⋯O and O-H⋯O hydrogen bonds, forming a three-dimensional network. Furthermore, there are face-to-face π-π stacking inter-actions between the centroids of one phenyl ring and the benzene ring of the 5-nitro-2-oxido-benzene-sulfonate group [centroid-centroid distance = 3.8382 (13) Å and slippage = 1.841 Å]. A Hirshfeld surface analysis was conducted to verify the contributions of the different inter-molecular inter-actions.

Trinuclear (aminonitrone)ZnII complexes as key intermediates in zinc(ii)-mediated generation of 1,2,4-oxadiazoles from amidoximes and nitriles

Amidoximes react with zinc salts in undried EtOAc furnishing the trinuclear species, where amidoximes are stabilized in the aminonitrone form.

DNA and BSA binding and cytotoxic properties of copper(ii) and iron(iii) complexes with arylhydrazone of ethyl 2-cyanoacetate or formazan ligands

Copper(ii) and iron(iii) complexes with arylhydrazone of ethyl 2-cyanoacetate or formazan ligands show DNA and BSA binding and anticancer abilities.

Resonance-Assisted Hydrogen Bonding as a Driving Force in Synthesis and a Synthon in the Design of Materials

Resonance-assisted hydrogen bonding (RAHB), a concept introduced by Gilli and co-workers in 1989, concerns a kind of intramolecular H-bonding strengthened by a conjugated π-system, usually in 6-, 8-, or 10-membered rings. This Review highlights the involvement of RAHB as a driving force in the synthesis of organic, coordination, and organometallic compounds, as a handy tool in the activation of covalent bonds, and in starting moieties for synthetic transformations. The unique roles of RAHB in molecular recognition and switches, E/Z isomeric resolution, racemization and epimerization of amino acids and chiral amino alcohols, solvatochromism, liquid-crystalline compounds, and in synthons for crystal engineering and polymer materials are also discussed. The Review can provide practical guidance for synthetic chemists that are interested in exploring and further developing RAHB-assisted synthesis and design of materials.

Reaction of sodium 2-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl) benzenesulfonate with ethylenediamine on Cu(ii) and Ni(ii) centres: efficient Cu(ii) homogeneous catalysts for cyanosilylation of aldehydes

Reaction of sodium 2-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)benzenesulfonate with ethylenediamine on Cu(ii) and Ni(ii) centres lead to variety of metal complexes which effectively catalyse the cyanosilylation of aldehydes with trimethylsilyl cyanide.

Mononuclear copper(ii) complexes of an arylhydrazone of 1H-indene-1,3(2H)-dione as catalysts for the oxidation of 1-phenylethanol in ionic liquid medium

Cu^II complexes of an arylhydrazone of 1H-indene-1,3(2H)-dione act as homogeneous catalysts for the microwave-assisted peroxidative oxidation of alcohols in ionic liquid medium.

Copper(ii) and iron(iii) complexes with arylhydrazone of ethyl 2-cyanoacetate or formazan ligands as catalysts for oxidation of alcohols

Cooperative coordination and ionic interactions assisted E/Z isomerization of arylhydrazone ligands lead to a variety of Cu^II complexes, which effectively catalyse the homogeneous oxidation of alcohols to carbonyl compounds.

Iron(iii) and cobalt(iii) complexes with both tautomeric (keto and enol) forms of aroylhydrazone ligands: catalysts for the microwave assisted oxidation of alcohols

Aroylhydrazone Fe(iii) and Co(iii) complexes of both keto and enol tautomeric forms of the ligand are reported and shown to catalyze the microwave-assisted solvent-free peroxidative oxidation (by TBHP) of primary and secondary alcohols.

Sulfonated Schiff base copper(ii) complexes as efficient and selective catalysts in alcohol oxidation: syntheses and crystal structures

Alcohol oxidation properties of four copper complexes (2–5) derived from the sulfonated Schiff base H₂L·3H₂O (1) are described. A quantitative conversion of 1-phenylethanol was obtained with 4 within 20 min of low power MW irradiation.

Lanthanide derivatives comprising arylhydrazones of β-diketones: cooperative E/Z isomerization and catalytic activity in nitroaldol reaction

RAHB and ionic interaction assisted E/Z→E isomerization of arylhydrazone of β-diketone is reported.

MnII and CuII complexes with arylhydrazones of active methylene compounds as effective heterogeneous catalysts for solvent- and additive-free microwave-assisted peroxidative oxidation of alcohols

Highly water-soluble Mn^II and Cu^II complexes are heterogeneous catalysts for solvent- and additive-free microwave-assisted peroxidative oxidation of less polar bulky substituted or long chain alcohols.