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Continuous-flow rhodium-catalysed hydroformylation of long chain alkenes has been achieved with selectivities to the desired linear aldehyde of 92% and minimum rhodium loss, using a xantphos-derived ligand attached to an imidazolium salt in a supercritical fluid–ionic liquid system. The effect of oxygen in the system can be ameliorated to some extent by adding a simple sulfonated triphenylphosphine to the catalytic solution. [ABSTRACT FROM AUTHOR]

Herein we disclosed the use of a remote ‘imidazole’‐based precatalyst [(para‐cymene)RuII(L)Cl]+, C‐1 where L=2‐(4‐substituted‐phenyl)‐1H‐imidazo[4,5‐f][1,10] phenanthroline) for the selective oxidation of a variety of alkyl arenes/heteroarenes and alcohols to their corresponding aldehydes or ketones in presence of tert‐butyl hydroperoxide (TBHP). The remote ‘imidazole’ moiety present in the complex facilitates the activation of oxidant and subsequent generation of active species via the release of para‐cymene from C‐1, which in‐turn was less effective without the ‘imidazole’ moiety. The mechanistic features of C‐1 promoted oxidation of alkyl arenes were also assessed from spectroscopic, kinetic, and few control experiments. The substrate scope for C‐1 promoted oxidation reaction was assessed based on the selective oxidation of 27‐different alkyl arenes/heteroarenes and 25 different alcohols to their corresponding aldehydes/ketones in moderate to good yields. [ABSTRACT FROM AUTHOR]

The catalytic aerobic oxidation of benzylic alcohols to corresponding aldehydes has been investigated employing a tetradentate copper(ii) complex that incorporates N-methyl imidazole (NMI) as an integral part of an N4-ligand framework. The complex [L3-Cu]2+ [(L3 = 1-methyl-4,5-dihydro-1H-imidazol-2-yl)methyl(2-ethyl)amine] has been synthesized, characterized by spectroscopic and structural techniques, and its catalytic activity towards the aerobic oxidation of benzylic alcohols studied under ambient conditions. Catalytic turnover required addition of the nitroxyl radical initiator TEMPO. No oxidation was observed with hydroxyl radical initiators H2O2 or tetrabutylammonium hydroperoxide. Additional NMI enhanced turnover with yields up to 99% within 4 hours. The relative quantities of substrate, catalyst, TEMPO, and NMI were systematically varied in a series of experiments to determine optimal conditions. The effect of oxygen at various flow rates as an alternate to ambient aerobic conditions was also investigated. [ABSTRACT FROM AUTHOR]

A simple and convenient approach is developed for the synthesis of the imidazo[1,2-f]phenanthridine framework via post-functionalization of imidazoles obtained through four-component reactions of 1,2-dicarbonyl compounds, anilines, aldehydes and ammonium acetate. The methodology involves palladium-catalyzed direct arylation through sp² C-H activation. The reported procedure delivers good to high yields of imidazo[1,2-f]phenanthridine derivatives (58-94%) starting from readily available precursors. [ABSTRACT FROM AUTHOR]

In this paper we describe the electro-oxidation of methyl-substituted aromatic compounds to the corresponding aldehydes in aqueous imidazole ionic liquid (IL) solutions and using a platinum electrode. The electro-oxidative behavior of p -methoxy toluene ( p -MT) was studied in the ILs using cyclic voltammetry (CV), and the oxidation was shown to be an irreversible process. Increasing the acid strength of the ILs led to further oxidation to the corresponding acid. The controlled potential electrolysis of methyl-substituted aromatic compounds was also investigated under the optimized reaction conditions and the products were detected by NMR, IR and gas chromatography/mass spectrometry (GC/MS). The method represents a promising way to prepare aromatic aldehydes. In order to detect intermediates, in-situ Fourier transform infrared spectroscopy (in-situ FTIR) data was acquired during the oxidation processes. The results further confirmed that the procedure provides a selective approach to the synthesis of aromatic aldehydes. The selectivity toward formation of the corresponding aromatic aldehydes was 21–92% when using the optimized reaction conditions. Excellent electrochemical stability of the ILs was demonstrated and they could be recycled at least 35 times. [ABSTRACT FROM AUTHOR]

Various imidazolium salts bearing hydrophilic groups were prepared that reacted with copper powder to afford watersoluble copper complexes of N-heterocyclic carbenes. These copper complexes can catalyze the selective oxidation of benzyl alcohols to the corresponding aldehydes in water at room temperature without the need for a base. [ABSTRACT FROM AUTHOR]

A facile and simple route for the direct preparation of substituted 3-methylcyclohex-2-enone via Aldol-Robinson cascade reaction of aldehydes and acetones catalyzed by the new catalytic system of L-lysine/imidazole in n-heptane with 0.5% water was reported. A variety of substrates can participate in the process efficiently. The merits of this method included inexpensive and easily available starting materials and catalyst, the good yield of products and the straightforward work-up. [ABSTRACT FROM AUTHOR]

One-pot reactions of aldehydes, 2-aminopyridines, and terminal alkynes, in the presence of the copper(I) iodide– NaHSO4·SiO2 combination catalyst in refluxing toluene, generate the corresponding imidazo[1,2-a]pyridines in high to excellent yields; the mechanism has been studied. [ABSTRACT FROM AUTHOR]

A facile, two-step, asymmetric synthesis of 3-substituted phthalides has been developed. The enantiopure amide, obtained through coupling of 2-iodobenzoic acid with (S)-1-(pyrrolidin-2-ylmethyl)- 1H-imidazole, was magnesiated using isopropylmagnesium chloride. Corresponding reactions with a range of aldehydes were carried out in situ by either direct addition or transmetallation using zinc(II) chloride. Intramolecular esterification of the adduct allowed the versatile asymmetric synthesis of phthalides in up to 88% enantiomeric excess. [ABSTRACT FROM AUTHOR]

The reaction between 1-methylimidazole, cyano(phenyl) acetylene, and 1-vinylpyrrole-2-carbaldehydes (MeCN, 20-25 °C) stereoselectively gives 1-vinylpyrrole-imidazole ensembles with a (Z,Z)-bis(2-cyano-1-phenylvinyl)oxy function in up to 45% yield. Unlike recently reported three-component reaction between imidazoles, electron-deficient acetylenes, and aldehydes affording 1:1:1 adducts, in this case two molecules of acetylene are involved to deliver 1:2:1 adducts thus representing a novel functionalizaton of the pyrrole-imidazole alkaloid scaffold. The initial zwitterion generated from imidazole and cyano(phenyl)acetylene is thought to be transformed into a carbene, which reacts with pyrrole-2-carbaldehyde. Two subsequent rearrangements of the 1:1:1 adduct furnish the intermediate pyrrole-imidazole ensemble, which in its enol form adds to second molecule of cyano(phenyl)acetylene to yield the final products, functionalized pyrrole-imidazole alkaloids. [ABSTRACT FROM AUTHOR]

N-{trans-3-[(5-Cyano-6-methylpyridin-2-yl)oxy]-2,2,4,4-tetramethylcyclobutyl}imidazo[1,2-a]pyrimidine-3-carboxamide (1) was recently identified as a full antagonist of the androgen receptor, demonstrating excellent in vivo tumor growth inhibition in castration-resistant prostate cancer (CRPC). However, the imidazo[1,2-a]pyrimidine moiety is rapidly metabolized by aldehyde oxidase (AO). The present paper describes a number of medicinal chemistry strategies taken to avoid the AO-mediated oxidation of this particular system. Guided by an AO protein structure-based model, our investigation revealed the most probable site of AO oxidation and the observation that altering the heterocycle or blocking the reactive site are two of the more effective strategies for reducing AO metabolism. These strategies may be useful for other drug discovery programs. [ABSTRACT FROM AUTHOR]

A simple and efficient method for the synthesis of 2,4,5-triaryl-1H-imidazole derivatives in good to excellent yields by reaction between hexamethyldisilazane and arylaldehydes, benzyl alcohols, benzyl halides in molten tetrabutylammonium bromide as an inexpensive and non toxic solvent has been developed. The remarkable advantages of this method are the simple workup procedure, high yields of products, the use of an ionic liquid as a green solvent, and the availability of reagents. [ABSTRACT FROM AUTHOR]

Various β-hydroxy-substituted amidines were obtained starting from methyl serinates, aldehydes or ketones, and tosyl azide. These were converted via Mitsunobu intramolecular cyclization into enantiomerically pure methyl 2-alkyl-1-tosyl-4,5-dihydro- 1H-imidazole-4-carboxylates. [ABSTRACT FROM AUTHOR]

The one-pot reaction of an aryl aldehyde with 2-cyanopyridine and ammonium acetate in refluxing acetic acid produced the known 2-(2′-pyridyl)imidazole and fused imidazoles. This suggests that the steric effect of aryl rings plays an important role in these syntheses. A possible mechanism of the reaction is discussed. [ABSTRACT FROM AUTHOR]

The compound 1,1′‐(ethane,1,2‐diyl)ditriphenylphosphonium hexamolybdate dimethylsulfoxide {C2H4[P(C6H5)3]2}{Mo6O19}·SO (CH3)2 (I) was prepared, and 1H‐NMR, 13C‐NMR, Fourier transform‐infrared, differential scanning calorimetry and single crystal X‐ray diffraction analysis were used to characterize the titled compound. Crystallographic data showed that compound I crystallized in the monoclinic crystal system in C2/c space group. The compound (I) was used for selective synthesis of 2,4,5‐tri aryl imidazole derivatives under solvent‐free conditions efficiently. Because of hindrance of the catalyst, the yields of products for aldehydes bearing para substituents are higher than the aldehydes bearing ortho substituents, and for aromatic aldehydes with meta substituents are very low. [ABSTRACT FROM AUTHOR]

Diastereoselective synthesis of pyrrolo[1,2‐c]imidazoles is reported from three‐component reaction of chiral thiohydantoins, aldehydes, and malononitrile in the presence of NEt3. The antioxidant properties of the obtained products were evaluated by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging assay. Among the products, compound 4l possessing NH2 and NH groups and bromine atom at 4‐position of the aromatic ring displayed the highest antioxidant activity (90%). Also, their antibacterial activities were explored against gram‐positive and gram‐negative bacteria using disc diffusion method. Among the synthesized compounds, 4a with chlorine atom at para position of the aromatic ring, and methyl group (the smallest alkyl group) at 7‐position, displayed the best antibacterial activity against the tested gram‐positive bacteria. [ABSTRACT FROM AUTHOR]

1‐Methyl imidazole‐based ionic liquid‐stabilized silica‐coated Fe3O4 magnetic nanoparticles [Fe3O4@SiO2@(CH2)3‐1‐methyl imidazole]HSO4 as a solid acid magnetic nanocatalyst was explored in the synthesis of pyrano[2,3‐d]pyrimidine derivatives. Pyrano[2,3‐d]pyrimidine derivatives were synthesized by a highly efficient three‐component reaction of various benzaldehydes, malononitrile, and barbituric acid. The catalyst was characterized by using various analysis techniques such as Fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry‐thermogravimetry analysis (DSC‐TGA), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). 1‐Methyl imidazole‐based ionic liquid‐stabilized silica‐coated FE3O4 magnetic nanoparticles [Fe3O4@SiO2@(CH2)3‐1‐methyl imidazole]HSO4 as a solid acid magnetic nanocatalyst was explored in the synthesis of pyrano[2,3‐d]pyrimidine derivatives with a yield of 95%. The magnetic catalyst could be readily separated and reused. [ABSTRACT FROM AUTHOR]

A one‐pot, two‐step, simple, efficient and eco‐friendly oxidation of internal alkynes as a key step towards the synthesis of 2,4,5‐trisubstituted imidazoles, using an inexpensive I2/DMSO system, has been reported. This metal and acid‐free synthesis proceeded smoothly to furnish a variety of synthetically useful trisubstituted imidazoles in moderate to excellent yields. In an effort to demonstrate the potential future applications of this system, a double oxidation study was undertaken and the desired trisubstituted imidazoles obtained in good to moderate yields. A one‐pot, two‐step, simple, efficient and eco‐friendly oxidation of internal alkynes as a key step towards the synthesis of 2,4,5‐trisubstituted imidazoles, using an inexpensive I2/DMSO system, has been reported. This metal and acid‐free reaction proceeded smoothly to furnish a variety of substituted imidazoles in moderate to excellent yields. [ABSTRACT FROM AUTHOR]

Citrate trisulfonic acid (CTSA), as a novel recyclable and eco‐benign organocatalyst, was employed for the efficient and one‐pot synthesis of trisubstituted imidazoles and tetrasubstituted imidazoles using aldehydes, ammonium acetate or aniline, and benzoin, benzyl, or 9,10‐phenanthrenequinone under solvent‐free conditions providing high to excellent yields. CTSA is easily prepared via the reaction of trisodium citrate and chlorosulfonic acid in high purity. Compared to the conventional procedures, the present method offers several advantages, including high yields, easy work‐up, short reaction time, reusability of the catalyst, and simple purification of the products. Citrate trisulfonic acid (CTSA), as a novel, recyclable, and eco‐benign organocatalyst, was applied for the efficient and one‐pot synthesis of 2,4,5‐trisubstituted imidazoles and 1,2,4,5‐tetrasubstituted imidazoles using aldehydes, benzoin, benzil or 9,10‐phenanthrenequinone and ammonium acetate or aniline under solvent‐free conditions providing high to excellent yields. CTSA is easily prepared via the reaction of trisodium citrate and chlorosulfonic acid in high purity. [ABSTRACT FROM AUTHOR]

Facile access to diverse C5‐substituted imidazoles and oxazoles via sequential Van Leusen–Suzuki, Van Leusen–Heck, and Van Leusen–Sonogashira protocols, employing imidazolium‐ILs as solvents along with piperidine‐appended imidazolium [PAIM][NTf2] as task‐specific basic IL has been demonstrated, in a high‐yielding one‐pot method, starting with readily available aldimines (for imidazole) or aldehydes (for oxazole) and tosylmethylisocyanide (Tos‐MIC), under mild conditions with potential for recycling and reuse of the IL solvent. The scope of the method is supported 49 examples. By sequencing the Van Leusen imidazole and oxazole syntheses with Suzuki, Heck and Sonogashira reactions, diverse libraries of C5‐functionalized imidazoles and oxazoles were synthesized in one‐pot reactions employing [BMIM][X] as a solvent and [PAIM][NTf2] as a base. [ABSTRACT FROM AUTHOR]

A facile and efficient cyclo-condensation reaction of substituted ortho-phenylenediamines with an aldehyde or carboxylic acid using etidronic acid to furnish hitherto unreported Methyl 4-methyl-2-substituted- 1H-benzo[d]imidazole-6-carboxylatederivatives was described. A new and efficient protocol was developed as a homogenous catalyst for the synthesis of benzimidazoles under conventional and microwave irradiated reaction atmosphere. This methodology has the advantage of excellent yields with short reaction time and highly robust & practical reaction arrangement. [ABSTRACT FROM AUTHOR]

1,4-Diazabicyclo[2.2.2]octane tribromide supported on magnetic Fe3O4 nanoparticles (MNPs-DABCO tribromide) as a novel heterogeneous tribromide type compound was found to be an efficient and reusable nanocatalyst for the one-pot synthesis of 2-arylquinazolin-4(3H)-ones and 2-aryl-1H-benzo[d]imidazoles through oxidative cyclization of aldehydes with 2-aminobenzamides and 1,2-phenylenediamine, respectively. Also, MNPs-DABCO tribromide catalyzed trimethylsilylation/tetrahydropyranylation and desilylation/depyranylation of a wide variety of alcohols and phenols through changing the solvent medium at room temperature. [ABSTRACT FROM AUTHOR]

Morpholinium hydrogen sulfate as an ionic liquid was employed as a catalyst for the synthesis of a biologically active series of multi-substituted imidazoles by a four-component reaction involving the combination of benzil with different aromatic aldehydes, ammonium acetate, and 1-amino-2-propanol under solvent-free conditions. The key advantages of this method are shorter reaction times, very high yield, and ease of processing. Furthermore, the resulting products can be purified by a non-chromatographic method and the ionic liquid catalyst is reusable. All of these novel compounds have been fully characterized from spectral data. The X-ray crystal structures of two representative molecules are also detailed. [ABSTRACT FROM AUTHOR]

A synergistic catalysis combination of chiral-at-metal rhodium complex and amine catalyst was developed for enantioselective alkylation of aldehydes with α, β-unsaturated 2-acyl imidazoles. The corresponding adducts were obtained in good yields with excellent enantioselectivities (up to 99% ee). [ABSTRACT FROM AUTHOR]

An operationally simple and efficient, one-pot, two-step methodology has been developed for the assembly of medicinally important imidazo[1,5- a]quinoxalines. The protocol involves the multicomponent reaction of aryl aldehydes, ortho- N-Boc-phenylenediamines and azidochalcones in the presence of erbium triflate as a Lewis acid catalyst, followed by deprotection-cyclization with 10% trifluoroacetic acid, furnishing the desired compounds in moderate to good yields. By virtue of their convergence, two aromatic rings and four new bonds are generated during the course of this reaction protocol. The structure of one of the compounds was proved by X-ray crystallography. [ABSTRACT FROM AUTHOR]

The rapid and expedient assembly of three new classes of biheterocycles of biological interest, viz. indole-imidazoles 4, indole-pyrroles 6 and indole-triazoles 8 was accomplished using different combinations of tryptamines, 1,2-diaza-1,3-dienes, aldehydes, and/or alkynes as readily available building blocks. Twenty-six derivatives were thus prepared in excellent yields (up to 100 %). The products were screened for in-vitro biological studies. Some of these revealed promising anticancer activity against MCF7 and Caco-2 human tumor cell lines. [ABSTRACT FROM AUTHOR]

The metal-free regioselective C-2-H functionalization of 1-substituted imidazoles has been effected by a cascade reaction with aromatic or heteroaromatic aldehydes and acylacetylenes under mild conditions (55-60 °C, MeCN) to give (imidazol-2-yl)methyl-1,3-propanediones in 22-77 %, mainly 40-70 % yields. [ABSTRACT FROM AUTHOR]

A multicomponent domino reaction of thiourea, alkyl propiolates, aldehydes, and isocyanides has been established, providing direct access to 2-aryl-5 H-imidazo[2,1- b][1,3]thiazin-5-one scaffolds. The simplicity of execution, readily available substrates, cheap reagents, high yields, excellent functional group tolerance, scalability, and good scores of environmental parameters make this synthetic strategy more efficient and worthy of further attention. [ABSTRACT FROM AUTHOR]

Biological function arises by the assembly of individual biomolecular modules into large aggregations or highly complex architectures. A similar strategy is adopted in supramolecular chemistry to assemble complex and highly ordered structures with advanced functions from simple components. Here we report a series of diamond-like supramolecular frameworks featuring mesoporous cavities, which are assembled from metal-imidazolate coordination cages and various anions. Small components (metal ions, amines, aldehydes, and anions) are assembled into the hierarchical complex structures through multiple interactions including covalent bonds, dative bonds, and weak CH⋅⋅⋅X (X=O, F, and π) hydrogen bonds. The mesoporous cavities are large enough to trap organic dye molecules, coordination cages, and vitamin B12. The study is expected to inspire new types of crystalline supramolecular framework materials based on coordination motifs and inorganic ions. [ABSTRACT FROM AUTHOR]

α-Hydrogen-substituted nitroxyl radicals are of considerable interest as catalysts for oxidation and polymerization, but are usually inherently unstable. We report herein the catalytic activity of a new family of stable iso-azaphenalene (IAPNO) α-hydrogen nitroxyl radicals in the copper/bipyridine/ N-methylimidazole co-catalyzed aerobic oxidation of alcohols. The nitroxyl radical Mes/TIPSO-IAPNO (TIPSO=triisopropyloxy, IAPNO=isoazaphenalene N-oxyl) displays higher activity than TEMPO in the oxidation of benzylic and allylic alcohols. Alkyl, benzyl, allyl, and propargyl alcohols are oxidized with yields up to 96 %. The readily prepared nitroxyl catalysts are recovered in 75-90 % yield after purification of the reaction mixture and are recycled. [ABSTRACT FROM AUTHOR]

A novel C1-symmetric dinitrogen ligand was synthesized in high yield from commercially available (1R,2R,3R,5S)-(-)-isopinocampheylamine and 1-methyl-2- imidazolecarboxaldehyde. In combination with Cu(OAc)2.H2O, this new ligand promote the reaction between nitromethane and aliphatic aldehydes with high yields (up to 97%) and moderate enantioselectivities (up to 67% ee). The reactions with benzaldehyde required prolonged reaction time that resulted in diminished yields, but accompanied with ee-values in the 55%-76% range. [ABSTRACT FROM AUTHOR]

A simple, practical, and efficient approach to new series of imidazole containing bisazetidinones ( 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h, 7i, 7j and 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, 9i, 9j) was prepared by Staudinger [2 + 2] , and bisthiazolidinones ( 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h, 8i, 8j and 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10i, 10j) were obtained by of bisimines with thioglycolic acid. The bisimines ( 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 5j and 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, 6i, 6j) were synthesized by the condensation of 3-(1-(3-aminobenzyl)-4, 5-dihydro-1H-imidazol-2-yl) aniline ( 3, 4) with a series of different substituted aromatic aldehydes. All the newly synthesized target compounds were evaluated for their in vitro against two Gram-positive bacteria and two Gram-negative bacteria. Additionally, these synthesized compounds were tested for their antifungal activities. Few compounds showed very good antibacterial and antifungal activity. [ABSTRACT FROM AUTHOR]

A series of benzimidazole-linked porous polymers are obtained by the condensation reaction between the o-aminobenzol end groups of building blocks (2,3,6,7,10,11-hexaaminotriphenylene, 3,3′-diaminobenzidine or 1,2,4,5-benzenetetraamine) and the aldehyde groups of building blocks [terephthalicaldehyde, 4,4′-biphenyldicarboxaldehyde, 1,3,5-tris(4-acetylphenyl)benzene or 1,3,5-tris(4-formylbiphenyl)amine] in one-pot synthesis without employing any catalyst or template. The existence of the imidazole ring in the obtained polymers could be identified by Fourier transform infrared and solid-state 13C CP/MAS NMR spectroscopy. The sphere-shaped morphology of the obtained polymers is observed through scanning electron microscopy. The polymers possess Brunauer-Emmett-Teller specific surface area values over 600 m2·g−1, showing hydrogen storage (up to 1.6 wt%, at 77 K and 1×105 Pa) and carbon dioxide capture (up to 12.6 wt%, at 273 K and 1×105 Pa) properties. Such polymers would possess good performance in the applications of gas storage and separation. [ABSTRACT FROM AUTHOR]

Alcohols are oxidized by N-methylmorpholine- N-oxide (NMO), ButOOH and H2O2 to the corresponding aldehydes or ketones in the presence of catalyst, [RuH(CO)(PPh3)2(SRaaiNR′)]PF6 ( 2) and [RuCl(CO)(PPh3)(SκRaaiNR′)]PF6 ( 3) (SRaaiNR′ ( 1) = 1-alkyl-2-{( o-thioalkyl)phenylazo}imidazole, a bidentate N(imidazolyl) (N), N(azo) (N′) chelator and SκRaaiNR′ is a tridentate N(imidazolyl) (N), N(azo) (N′), Sκ-R is tridentate chelator; R and R′ are Me and Et). The single-crystal X-ray structures of [RuH(CO)(PPh3)2(SMeaaiNMe)]PF6 ( 2a) (SMeaaiNMe = 1-methyl-2-{( o-thioethyl)phenylazo}imidazole) and [RuH(CO)(PPh3)2(SEtaaiNEt)]PF6 ( 2b) (SEtaaiNEt = 1-ethyl-2-{( o-thioethyl)phenylazo}imidazole) show bidentate N,N′ chelation, while in [RuCl(CO)(PPh3)(SκEtaaiNEt)]PF6 ( 3b) the ligand SκEtaaiNEt serves as tridentate N,N′,S chelator. The cyclic voltammogram shows RuIII/RuII (~1.1 V) and RuIV/RuIII (~1.7 V) couples of the complexes 2 while RuIII/RuII (1.26 V) couple is observed only in 3 along with azo reductions in the potential window +2.0 to −2.0 V. DFT computation has been used to explain the spectra and redox properties of the complexes. In the NMO acts as best oxidant and [RuCl(CO)(PPh3)(SκRaaiNR′)](PF6) ( 3) is the best catalyst. The formation of high-valent RuIV=O species as a catalytic is proposed for the oxidation process. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Metalmetal singly-bonded diruthenium complexes, bridged by naphthyridine-functionalized N-heterocyclic carbene (NHC) ligands featuring a hydroxy appendage on the naphthyridine unit, are obtained in a single-pot reaction of [Ru2(CH3COO)2(CO)4] with 1-benzyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazolium bromide (BIN ⋅HBr) or 1-isopropyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazolium bromide (PIN ⋅HBr), TlBF4, and substituted benzaldehyde containing an electron-withdrawing group. The modified NHC-naphthyridine-hydroxy ligand spans the diruthenium unit in which the NHC carbon and hydroxy oxygen occupy the axial sites. All the synthesized compounds catalyze acceptorless dehydrogenation of alcohols to the corresponding aldehydes in the presence of a catalytic amount of weak base 1,4-diazabicyclo[2.2.2]octane (DABCO). Further, acceptorless dehydrogenative coupling (ADHC) of the alcohol with amines affords the corresponding imine as the sole product. The substrate scope is examined with 1 (BIN, p-nitrobenzaldehyde). A similar complex [Ru2(CO)4(CH3COO)(3-PhBIN)][Br], that is devoid of a hydroxy arm, is significantly less effective for the same reaction. Neutral complex 1 a, obtained by deprotonation of the hydroxy arm in 1, is found to be active for the ADHC of alcohols and amines under base-free conditions. A combination of control experiments, deuterium labeling, kinetic Hammett studies, and DFT calculations support metal-hydroxyl/hydroxide and metal-metal cooperation for alcohol activation and dehydrogenation. The bridging acetate plays a crucial role in allowing β-hydride elimination to occur. The ligand architecture on the diruthenium core causes rapid aldehyde extrusion from the metal coordination sphere, which is responsible for exclusive imine formation. [ABSTRACT FROM AUTHOR]

The ruthenium-catalyzed hydroformylation of 1- and 2-octene to give preferentially the corresponding linear aldehyde is reported. The catalyst system comprising of Ru3(CO)12 and an imidazole-substituted monophosphine ligand allows for high chemo- and regioselectivity. The hydroformylation proceeds with unprecedented rates for a ruthenium-based catalyst. [ABSTRACT FROM AUTHOR]

Antimony trichloride absorbed on silica gel (SbCl/SiO) efficiently catalyses the four-component cyclocondensation of 1,2-diketone, aldehyde, ammonium acetate, and primary amine under solvent-free conditions to afford the corresponding tetrasubstituted imidazoles in high yields. The main merit of this study is introducing a novel catalyst to successful synthesis of a wide range of 1,2,4,5-tetrasubstituted imidazoles for the first time. The proposed method involves features such as simplicity, generality, fairly good efficiency, and reusability of the catalyst. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

An environmentally benign and efficient method has been developed for the synthesis of a series of benzo[4,5]imidazo[1,2-a]pyrimido[4,5-d]pyrimidin-4(1H)-one derivatives in aqueous media under catalyst-free conditions by simply combining 2-aminobenzimidazole, aldehyde, and cyanoacetamide. The advantages of this method are that it is catalyst-free, has an easy workup, provides excellent yields, and uses water as the solvent which is considered to be relatively environmentally benign. [ABSTRACT FROM AUTHOR]

Four new y-shaped fluorophores of 4- {4,5-[2,2′-Bis(2,4,6-trimethoxyphenyl)vinyl]-1-H-imidazole-2-yl}benzonitrile 1a, 2-phenyl-{4,5-[2,2′-Bis(2,4,6-trimethoxyphenyl)vinyl]-1-H-imidazole} 1b, 2- (9-anthryl)-{4,5-[2,2′-Bis(2,4,6-trimethoxyphenyl)vinyl] }-1-H-imidazole 1c and 2- (4-nitrophenyl) - {4,5-[2,2′-Bis(2,4,6-trimethoxyphenyl)vinyl] -1-H-imidazol e 1d which bear an imidazole core, were synthesized for the first time via intermediate 1,6-Bis(2,4,6-trimethoxyphenyl)hexa-1,5-diene-3,4-dion with different aldehydes. The structures of the new derivatives were confirmed by H NMR, C NMR and FT-IR. The optical properties such as absorption and emission maxima, Stokes' shift and quantum yield values were investigated in solvents of toluene, tetrahydrofuran and acetonitrile. The products show intense emission maxima in the range of 440-630 nm. The imidazole derivatives exhibited excellent photostabilities. [ABSTRACT FROM AUTHOR]

An efficient synthesis of 2,4,5-trisubstituted imidazoles is achieved by three component cyclocondensation of benzil or benzoin, aldehyde and ammonium acetate by using novel polymeric catalyst [poly(AMPS-co-AA)] under solvent-free conditions. The key advantages of this process are high yields, shorter reaction times, easy work-up, purification of products by non-chromatographic method and the reusability of the catalyst. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A simple, high-yielding synthesis of 2,4,5-trisubstituted imidazoles from 1,2-diketone/1,2-hydroxyketone and aldehydes in the presence of NH4OAc is described. Under solvent-free conditions, aryl and heteroaryl substituted imidazoles are formed in yields ranging from 70 to 90%. [ABSTRACT FROM PUBLISHER]

series of substituted imidazoles have been synthesized in very good yield under solvent free condition by grinding 1,2-diketone, aromatic aldehyde and ammonium acetate in the presence of molecular iodine as the catalyst. The short reaction time, good yield and easy workup make this protocol practically and economically attractive and characterized by NMR spectra, X-ray, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazoles (dpip and dptip) have been studied using emission spectroscopy and it was detected that the two distinct ground state rotamers are responsible for the normal and the tautomer emissions. DFT calculations on energy, dipole moment, charge distribution of the rotamers in the ground and excited states of the imidazole derivatives were performed and discussed. DFT analysis about HOMO, HOMO-1, LUMO and LUMO + 1 were carried out and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than the ground state. [ABSTRACT FROM AUTHOR]

The tridentate ligand HL (HL = β-phenylalanine, N-[1-(2-hydroxyphenyl)propylidene] reacts with copper(II) nitrate and imidazole to give binuclear compound [CuL(imi)] ( 1). The coordination geometry of each copper(II) ion is best described as a square-pyramided with one nitrogen atom, two oxygen atoms of the ligand one nitrogen atom of imidazole and one carboxylate oxygen atom belong to another ligand. It crystallizes in the monoclinic system P−1 with a = 7.8439(12) Å, b = 10.2717(16) Å, c = 11.6885(18) Å, α = 76.672(2)°, β = 85.397(2)°, γ = 71.412(2)°, V = 868.6(2) Å, Z = 1. Index Abstract: Crystal structure of 1 [CuL(imi)] reveals a binuclear compound with eight-member ring (shown in green color), in which the coordination environment around each copper(II) ion exhibits a distorted square-pyramidal geometry [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

L-Proline triflate has been used as an efficient catalyst for an improved and rapid one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles in good yields. The benefit of this approach is its operational simplicity and the catalyst can be easily recovered and reused without any loss of activity. [ABSTRACT FROM AUTHOR]

A series of new, chiral Lewis bases containing imidazole -N-oxide moiety were tested for purposes of asymmetric catalysis. Bisimidazole- N-oxides derived from (1 R,2 R)- and (1 S,2 S)- TRANS-1,2-diaminocyclohexane were used as catalysts in the allylation reaction of aromatic aldehydes with allyltrichlorosilane, which yielded homoallyl alcohols in good yields and with enantioselectivity up to 80% ee. Screening of catalysts revealed that the type of substituents and their location in imidazole ring has a crucial influence on enantioselectivity of the addition process. [ABSTRACT FROM AUTHOR]

By combining a ceric ammonium nitrate (CAN)-catalyzed aerobic oxidation of α-hydroxy ketones with a subsequent three-component condensation reaction using aldehydes and ammonium acetate, highly substituted imidazole derivatives can be assembled. This reaction is an important approach for the synthesis of highly substituted imidazole derivatives and was carried out in good to excellent yields in ethanol as an environmentally benign solvent. [ABSTRACT FROM AUTHOR]

A simple, efficient, and practical procedure for synthesis of 2,4,5-trisubstituted-1H-imidazoles via the condensation of benzoin or acetoin, aromatic aldehydes, and ammonium acetate using europium triflate [Eu(OTf)3] as a novel catalyst in high yields is described. The catalyst can be recovered conveniently and reused at least four times without any loss of activity. [ABSTRACT FROM AUTHOR]

Planar chiral imidazolium salts 8 and 13 were used as precursors for N-heterocyclic carbene ligands, which were applied in rhodium-catalyzed additions of arylboronic acids to aromatic aldehydes. With pseudo-ortho-disubstituted [2.2]paracyclophane (S,Rp)-8b bearing a phosphinoyl substituent at the paracyclophane backbone, 38% ee has been achieved in this rather unexplored reaction. [ABSTRACT FROM AUTHOR]

Tautomerization of 2-phenylimidazolecarbaldehydes has not been studied in detail so far, although this process is a well-known phenomenon for imidazole derivatives. That is why we focus our study on a series of 2-phenylimidazolecarbaldehydes and their parent alcohols that were synthesized and studied by detailed 1H and 13C NMR in solution and in the solid state. The apparent problem is that the fast tautomerization impedes the full structural description of the compounds by conventional 13C NMR measurements. Indeed, the 13C NMR spectra in solution exhibit poor resolution, and in most cases, signals from the imidazole ring are not detectable. To avoid this problem, we used 13C CP-MAS NMR as an alternative spectroscopic method for unambiguous spectroscopic characterization of the studied series of 2-phenylimidazoles. The data were analyzed in combination with quantum chemical DFT-GIAO methods by considering the tautomerization process and the intermolecular interactions. The DFT (B3LYP/6-31G(d,p)) calculations allowed to identify and suggest the preferred tautomer in the gas phase and in DMSO solvent, which for alcohols are (2-phenyl-1H-imidazol-4-yl)methanol and its analogs, and for the aldehydes are the 2-phenyl-1H-imidazole-5-carbaldehydes. The gas-phase calculated energy differences between the two possible tautomeric forms are in the range 0.645–1.415 kcal/mol for the alcohols and 2.510–3.059 kcal/mol for the aldehydes. In the DMSO solvent, however, for all compounds, the calculated energy differences go below 1.20 kcal/mol. These data suggest that both tautomeric forms of the studied 2-phenylimidazoles can be present in solution at room temperature. Our data from detailed 2D NMR measurements in the solid state (1H-13C HETCOR and 1H-1H double-quantum coherence MAS NMR) suggested that also in the solid state both tautomers coexist in different crystalline domains. This fact does not obscure the 13C CP-MAS NMR spectra of the studied 2-phenyl substituted imidazoles and suggests this spectroscopic method as a powerful tool for a complete structural description of tautomeric systems with aromatic conjugation. [ABSTRACT FROM AUTHOR]