Molybdenum(II)-catalyzed alkylation of electron-rich aromatics with allylic acetates

The molybdenum(II) complex [Mo(CO)₄Br₂]₂ has been found to catalyze allylic substitution with aromatic ethers, e.g., anisole (7), as nucleophiles. The reaction is remarkably para-selective (e.g., 7 + 8 → 11).     

New Gilman-type lithium cuprate from a copper(II) salt: synthesis and deprotonative cupration of aromatics

Deprotonative cupration of aromatics including heterocycles (anisole, 1,4-dimethoxybenzene, thiophene, furan, 2-fluoropyridine, 2-chloropyridine, 2-bromopyridine, and 2,4-dimethoxypyrimidine) was realized in tetrahydrofuran at room temperature using the Gilman-type amido-cuprate (TMP)₂CuLi in situ prepared from CuCl₂·TMEDA through successive addition of 1 equiv of butyllithium and 2 equiv of LiTMP. The intermediate lithium (hetero)arylcuprates were evidenced by trapping with iodine, allyl bromide, methyl iodide, and benzoyl chlorides, the latter giving the best results. Symmetrical dimers were also prepared from lithium azine and diazine cuprates using nitrobenzene as an oxidative agent.     

A New Method for the Oxybromination of Aromatic Compounds with Copper(II)bromide and Potassium Dichromate

Abstract

A new and mild method for oxybromination of aromatic compounds with CuBr ₂ and K ₂ Cr ₂ O ₇ in HOAC is reported.     

Copper(II)-catalyzed reactions of activated aromatics

The catalytic reaction of cis-bisglycinato copper(II) monohydrate in the presence of hydrogen peroxide leads to hydroxylation of phenol to give catechol and hydroquinone (1:1.2 ratio) in good yield. 2,6-Dimethylphenol can be hydroxylated by hydrogen peroxide and a catalytic amount of cis-bisglycinato copper(II) monohydrate to give an aggregate of 1,4-dihydroxy-2,6-dimethylbenzene and 2,6-dimethylphenol. A similar reaction of o-cresol gives 2,5-dihydroxytoluene. The reactivity of cis-bisglycinato copper(II) monohydrate in hydrogen peroxide with o-cresol is 4.5 times faster than that of a similar reaction by trans-bisglycinato copper(II) monohydrate. A catalytic reaction of cis-bisglycinato copper(II) monohydrate with aniline in aqueous hydrogen peroxide gives polyanilines in the form of pernigraniline with different amounts of Cu(OH)2 attached to them. The two major components of polyanilines obtained have Mn values of 1040 and 1500, respectively. Resistance of films of these polyanilines increases with temperatures from 40 degrees C to a maximum value at 103 degrees C and then decreases in the region of 103-150 degrees C, showing the property of a thermolectric switch. The aggregate prepared from hydroxylation of 2,6-dimethylphenol shows a similar property in the region of 30-180 degrees C.     

Friedel-Crafts trifluoromethylthiolation of electron-rich (hetero)arenes with trifluoromethylthio-saccharin in 2,2,2-trifluoroethanol (TFE)

A promoter-free Friedel-Crafts trifluoromethylthiolation of electron-rich arenes and heteroarenes with N-trifluoromethylthiosaccharin 5 using 2,2,2-trifluoroethanol (TFE) as the solvent was described.     

Friedel-Crafts trifluoromethylthiolation of electron-rich (hetero)arenes with trifluoromethylthio-saccharin in 2,2,2-trifluoroethanol (TFE)

A promoter-free Friedel-Crafts trifluoromethylthiolation of electron-rich arenes and heteroarenes with N-trifluoromethylthiosaccharin 5 using 2,2,2-trifluoroethanol (TFE) as the solvent was described. The reactions were conducted at 40 °C and a variety of common functional groups were compatible.     

Observations on the copper(II) catalyzed reactions of enaminones and dimethyl diazomalonate

The Cu(acac)₂ catalyzed reactions of dimethyl diazomalonate with enaminones yielded 1,5-cyclization and α-CH insertion products. In the case of anilino derivatives (R¹ or R² = Ph), products resulting from an unusual insertion to the benzoyl ring dominated the reaction.     

Recent advances in transition-metal-catalyzed asymmetric reactions of diazo compounds with electron-rich (hetero-) arenes

The transition-metal-catalyzed reaction of diazo compounds with arenes or heteroarenes is an efficient and straightforward approach to functionalize aromatic compounds. This digest summarizes recent progresses on transition-metal-catalyzed asymmetric reactions of diazo compounds with electron-rich (hetero-) arenes, including C–H functionalization, cascade reaction, cyclopropanation, cycloaddition, Buchner reaction and intramolecular dearomatization.     

Nucleophilic substitution of hydrogen in naphthalene by chloride(Cl~-)in ionic liquids

Nucleophilic aromatic substitution of hydrogen in non-activated aromatic ring,a very rare phenomenon in organic chemistry,is found in ionic liquids containing Cl^- as anion under mild reaction conditions.The reaction may be carried out by the addition of the halogen-bonding adduct（Br₂Cl^-） as nucleophile to aromatic ring carbon atom,leading to the formation of the nucleophilic substitution product.     

Ultrasound-promoted aromatic nucleophilic substitution of dichlorobenzene iron(II) complexes

The nucleophilic aromatic substitution under ultrasound irradiation of a dichlorobenzene iron η⁶-complex with various secondary amines is reported. The reaction time at moderate temperatures is considerably shortened (15 min) compared to non sonicated reaction conditions at room temperature (several days) or at solvent refluxing temperature (12-48 h). Controlled mono- or di-substitution was achieved by the tuning of the amine nucleophilicity and the solvent polarity. The method was successfully applied to the synthesis of differently substituted phenylenediamines.     

Determination of trace amounts of mercury(II) in water samples using a novel kinetic catalytic ligand substitution reaction of hexacyanoruthenate(II)

A simple, sensitive, selective and rapid kinetic catalytic method has been developed for the determination of Hg(II) ions at micro-level. This method is based on the catalytic effect of Hg(II) ion on the rate of substitution of cyanide in hexacyanoruthenate(II) with nitroso-R-salt (NRS) in aqueous medium and provides good accuracy and precision. The concentration of Hg(II) catalyst varied from 4.0 to 10.0 × 10⁻⁶ M and the progress of reaction was followed spectrophotometrically at 525 nm (λ_max of purple-red complex [Ru(CN)₅NRS]³⁻,  = 3.1 × 10³ M⁻¹ s⁻¹) under the optimized reaction conditions; 8.75 × 10⁻⁵ M [Ru(CN)₆⁴⁻], 3.50 × 10⁻⁴ M [nitroso-R-salt], pH 7.00 ± 0.02, ionic strength, I = 0.1 M (KCl), temp 45.0 ± 0.1 °C. The linear calibration curves, i.e. calibration equations between the absorbance at fixed times (t = 15, 20 and 25 min) versus concentration of Hg(II) ions were established under the optimized experimental conditions. The detection limit was found to be 1.0 × 10⁻⁷ M of Hg(II). The effect of various foreign ions on the proposed method has also been studied and discussed. The method has been applied to the determination of mercury(II) in aqueous solutions.     

An investigation of comparative substitution behavior of bifunctional trans-platinum(II) complexes with symmetric and asymmetric alkylamine ligands

This study was undertaken to investigate the comparative substitution behavior of mononuclear trans-platinum(II) complexes with symmetric and asymmetric amine ligands. The rate of substitution of the aqua moeities from the complexes trans-[Pt(NH₃)₂(H₂O)₂](ClO₄)₂ (tPt), trans-[Pt(NH₃)(NH₂C₂H₅)(H₂O)₂](ClO₄)₂ (tPt2H₂O), trans-[Pt(NH₃)(NH₂C₃H₇)(H₂O)₂](ClO₄)₂ (tPt3H₂O), [trans-Pt(OH₂)₂(NH₂CH₃)₂](ClO₄)₂ (tPtM), and [trans-Pt(OH₂)₂{NH₂CH(CH₃)₂}₂](ClO₄)₂ (tPtR), by three nucleophiles, namely thiourea (TU), 1,3-dimethylthiourea (DMTU), and 1,1,3,3-tetramethylthiourea (TMTU) was studied under pseudo–first-order conditions as a function of concentration and temperature by stopped-flow spectrophotometry. All the substitution reactions of each of the trans-platinum(II) complexes proceeds by a stepwise mechanism involving rate-determining substitution of the first aqua ligand followed by a fast second substitution step, without any intermediates formed. The reactions were second order overall (rate = k_obs[complex] where k_obs = k₂[nucleophile]), first order in both [complex] and [nucleophile]. The reactivity of the complexes was essentially governed by both steric and electronic factors. Comparing the second-order rate constants for the substitution reactions of the mononuclear diaqua trans-platinum(II) complexes with the thiourea-based nucleophiles, the observed trend follows: tPt > tPt2H₂O > tPtM > tPt3H₂O > tPtR. This reactivity trend is consistent with the pK_a values obtained for the first deprotonation step. The reactivity of the nucleophiles with the complexes decreases with an increase in steric demand in the following order: TU > DMTU > TMTU. The low positive values of activation enthalpy and large negative values of activation entropy indicate an associative mechanism of substitution in all the complexes. The computational modeling using density functional theory calculations was employed to provide theoretical interpretation of kinetic data.     

Copper (II) Nitrate-Silica Gel Mediated Regeneration of Carbonyl Compounds from Oximes Under Microwave Irradiation

Cu(NO₃)₂ supported on silica gel can be used as an effective and mild oxidizing agent for the direct conversion of oximes to carbonyl compounds under microwave irradiation in good yield.     

New synthetic method of 1,2-diaryl-1,2-dicarba-closo-dodecaboranes employing aromatic nucleophilic substitution (SNAr) reaction

Aromatic nucleophilic substitution (S_NAr) reaction of 1-phenyl-o-carborane with 4-nitrofluorobenzene in the presence of NaH or KO^tBu proceeded smoothly to give 1-(4-nitrophenyl)-2-phenyl-o-carborane; similar reaction affords various 1,2-diaryl-o-carboranes, which are useful precursors for macromolecular construction and drug design.     

Effect of Successive Meso-Phenyl Substitution on the Dissociation Kinetics of Copper(II) Octaethylporphyrin

We have synthesized complexes of copper(II) with octaethyl-, 5-phenyl octaethyl-, 5,15-diphenyl octaethyl-, and 5,10,15,20-tetraphenyl octaethylporphyrins. We have studied their dissociation kinetics in mixed solvents AcOH – H₂SO₄ at temperatures of 298 K to 343 K. We have determined the complete kinetic equations for dissociation of copper porphyrins for different compositions of the binary solvent AcOH – H₂SO₄. We provide a rational basis for electronic and steric effects on the stability of copper(II) octaethylporphyrin upon meso-phenyl substitution as a function of the degree of substitution.     

Nucleophilic attack of intramolecular hydroxyl groups on electron-rich aromatics using hypervalent iodine(III) oxidation

The hypervalent iodine(III) reagent, phenyliodine bis(trifluoroacetate) (PIFA)-mediated oxidative nucleophilic substitution of electron-rich aromatics involving aromatic cation radical intermediates was utilized in the direct aromatic carbon-oxygen bond formation reaction, and a novel and simple synthetic method for chroman derivatives was developed. As an extension of this methodology, a facile access to spirodienone derivatives was also achieved.     

Aqua substitution from mononuclear Pt(II) complexes with 2-(pyrazol-1-ylmethyl)quinoline non-leaving ligands

The rates of aqua substitution from [Pt{2-(pyrazol-1-ylmethyl)quinoline}(H₂O)₂](ClO₄)₂, [Pt(H₂Qn)], [Pt{2-(3,5-dimethylpyrazol-1-ylmethyl)quinoline}(H₂O)₂](ClO₄)₂, [Pt(dCH₃Qn)], [Pt{2-[(3,5-bis(trifluoromethyl)pyrazol-1-ylmethyl]quinoline}(H₂O)₂](ClO₄)₂, [Pt(dCF₃Qn)], and [Pt{2-[(3,5-bis(trifluoromethyl)pyrazol-1-ylmethyl]pyridine}(H₂O)₂](ClO₄)₂, [Pt(dCF₃Py)], with three sulfur donor nucleophiles were studied. The reactions were followed under pseudo-first-order conditions as a function of nucleophile concentration and temperature using a stopped-flow analyzer and UV/visible spectrophotometry. The substitution reactions proceeded sequentially. The second-order rate constants for substituting the aqua ligands in the first substitution step increased in the order Pt(dCH₃Qn) < Pt(dCF₃Qn) < Pt(H₂Qn) < Pt(dCF₃Py), while that of the second substitution step was Pt(dCH₃Qn) < Pt(dCF₃Qn) < Pt(dCF₃Py) < Pt(H₂Qn). The reactivity trends confirm that the quinoline substructure in the (pyrazolylmethyl)quinoline ligands acts as an apparent donor of electron density toward the metal center rather than being a π-acceptor. Measured pK_a values from spectrophotometric acid–base titrations were Pt(H₂Qn) (pK_a1 = 4.56; pK_a2 = 6.32), Pt(dCH₃Qn) (pK_a1 = 4.88; pK_a2 = 6.31), Pt(dCF₃Qn) (pK_a1 = 4.07; pK_a2 = 6.35), and Pt(dCF₃Py) (pK_a1 = 4.76; pK_a2 = 6.27). The activation parameters from the temperature dependence of the second-order rate constants support an associative mechanism of substitution.     

Isocationic substitution of copper(II) complexes in anisotropic materials based on benzenetricarboxylate

A phase transfer isocationic substitution of lattice constituent macrocyclic complexes by copper(II) aqua complexes occurs upon the interaction of crystalline mono-and bis(macrocyclic) copper carboxylate complexes with acetonitrile solutions of copper(II) ammine complex. On the other hand, these materials do not react with cupric bis(ethylenediamine). __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 124–129, March–April, 2007.     

Two cadmium(II) addition compounds with 3-hydroxy-2,7-naphthalenedisulfonate containing aromatic diamines and their 3-D net

{[CdCl(2,2′-bipy)₂(H₂O)]⁺·[Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?·3H₂O} (1) and {[Cd(phen)₃]²⁺·2[Cd(3-O^?-2,7-NDS)(phen)₂]^?·8.5H₂O} (2) (3-OH-2,7-NDS?=?3-hydroxy-2,7-naphthalenedisulfonate, phen?=?1,10-phenanthroline, and 2,2′-bipy?=?2,2′-bipydine) were prepared and characterized by X-ray single-crystal diffraction. Compound 1 contains a discrete coordination cation [CdCl(2,2′-bipy)₂(H₂O)]⁺ and a coordination anion [Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?; 2 contains a discrete coordination cation [Cd(phen)₃]²⁺ and two coordination anions [Cd(3-O^?-2,7-NDS)(phen)₂]^?. There are numerous weak interactions among the coordination cation, coordination anion, and free water molecules, such as O–H?···?O hydrogen bonds, π?···?π stacking, and Cl^??···?π interactions in 1 and π?···?π stacking and C–H?···?π interactions in 2. The cations and anions as building blocks are connected to construct different 3-D supramolecular architectures via weak intermolecular interactions. Particularly, the capsule structure of 1 was observed.     

Synthesis,Structural and Energetic Properties of Copper(II) Perchlorate Complex with Aminoguanidine

The complexation of copper(II) perchlorate with aminoguanidine hemesulfate (AGHS) yield related mononuclear complex bis(aminoguanidine)copper(II) perchlorate; [Cu(AG)₂](ClO₄)₂ ( I ). The characterization of complex I was done by elemental analysis, electronic spectra, IR studies, and X‐ray diffraction. From analytical data, a stoichiometry of 1:2 of metal to ligand was determined for the complex. The structure consists of centrosymmetric square planar [Cu(AG)₂]²⁺ cations and perchlorate counterions. The Cu^II atom is four‐coordinate by two imine N atoms and two amine N atoms from two aminoguanidine ligands, forming a slightly distorted square‐planar coordination. In the crystal structure, molecules are linked through intermolecular N–H ··· O hydrogen bonds, forming a network. The thermal decomposition process of this complex was investigated through differential scanning calorimetry (DSC) and the sensitivities toward impact and friction were assessed using a BAM drophammer and a BAM friction tester.