Efficient and practical synthesis of 4(5)-aryl-1H-imidazoles and 2,4(5)-diaryl-1H-imidazoles via highly selective palladium-catalyzed arylation reactions

4(5)-aryl-1H-imidazoles can be efficiently and selectively prepared by PdCl2(dppf)-catalyzed Suzuki-Miyaura reaction of commercially available 4(5)-bromo-1H-imidazole with arylboronic acids under phase-transfer conditions. On the other hand, N-unprotected 4(5)-aryl-1H-imidazoles can undergo highly selective Pd(OAc)2-catalyzed and CuI-mediated direct C-2-arylation with a variety of aryl bromides and iodides under base-free and ligandless conditions to produce 2,4(5)-diaryl-1H-imidazoles in modest to good yields. No N-arylation byproducts are observed under the experimental conditions used to prepare 2,4(5)-diaryl-1H-imidazoles.     

Multi-step redox systems with NIR-fluorescence based on 4H-imidazoles

A new class of 4H-imidazoles was synthesized starting from fused-ring aromatic dinitriles. Strong bathochromic shifts of the longest wavelength absorptions were observed in the corresponding UV/vis spectra due to a conversion of the merocyanine chromophores into cyanines/(aza)oxonoles upon protonation/deprotonation of the 4H-imidazoles. Novel boratetraazapentalenes were synthesized via a cyclization reaction with boron trifluoride. These mesoionic species bearing a cyanine chromophore not only show NIR-fluorescence, they also participate as part of a quasi-reversible multi-step redox system. Large calculated semiquinone formation constants K(SEM) (3x10(10) to 5x10(11)) indicate a high thermodynamic stability of the corresponding radical anions (SEM).     

PEG-400 as an efficient reaction medium for the synthesis of 2,4,5-triaryl-1H-imidazoles and 1,2,4,5-tetraaryl-1H-imidazoles

An efficient protocol for the one-pot multicomponent synthesis of various 2,4,5-triaryl- IH-imidazoles and 1,2,4,5-tetraaryl-1H-imidazoles using PEG-400 as reaction medium is described. This method has the advantages of good yields, less pollution and simple reaction conditions.     

微波促进无溶剂无催化条件下2,4,5-三芳基取代咪唑衍生物的合成

咪唑及其衍生物具有广泛的生理活性,作为许多天然酶的活性中心功能基,它们参与了一系列重要的生物化学反应[1,2],被誉为“生物配体”或“生物催化剂”。近年来,人们发现咪唑及其衍生物也是一类重要的有机功能材料,它在制药、化学发光、有机光电等领域有着广泛的应用[3,4]。利用     

Reaction of 5-(2-furyl)-1-methyl-1<Emphasis Type="Italic">H-</Emphasis> and 1-methyl-5-(2-thienyl)-1<Emphasis Type="Italic">H</Emphasis>-imidazoles with electrophilic reagents

5-(2-Furyl)-1-methyl-1H- and 1-methyl-5-(2-thienyl)-1H-imidazoles were synthesized. The electronwithdrawing effect of the 5- and 2-imidazole substituents on the furan ring was studied by ¹H NMR spectroscopy and quantum-chemical calculations. Some electrophilic substitution reactions were investigated (nitration, bromination, sulfonation, hydroxymethylation, formylation, and acylation). In some cases, depending on the reaction conditions, both the furan and thiophene ring and the imidazole fragment undergo electrophilic attack.     

Functional masking of carbonyl group by 1-methyl-1H-imidazol-2-YL moiety

Easily obtained 1-methyl-2-(1′-hydroxyalkyl)-1H-imidazoles (4) were found to be a new type of masked form for carbonyl group which could survive under various severe conditions. The corresponding carbonyl compounds (3) were easily reproduced by quarternization of the imidazole (4) with CH₃I followed by aqueous basic treatment. 2-Acyl-1H-imidazoles (5) were convertible to aldehydes or ketones (3) by using the present methodology.     

Novel structural analogs of glyphosate based on azoles. 1. Synthesis of 1H-imidazoles containing carboxyl and phosphoryl groups in the ring

A general method has been developed for the synthesis of 1H-imidazoles containing a phosphoryl group in positions 2 or 4(5) based on lithium intermediates. The possibility of further functionalization of the ring using electrophiles has also been demonstrated.     

Design and Optimization of Ecofriendly One-Pot Synthesis of 2,4,5-Triaryl-1H-imidazoles by Three-Component Condensation Using Response Surface Methodology

Phase-transfer-catalyzed, highly versatile, and high-yielding protocol for the synthesis of 2,4,5-triaryl-1H-imidazoles was developed through response surface methodology (RSM). The effects of different solvents, reaction paths, and phase-transfer catalysts (PTCs) in different concentrations were envisioned. Three independent variables (catalyst, catalyst loading, and solvent volume) identified by one-factor-at-a-time (OFAT) study were screened through full factorial design at two levels. The analysis of variance results suggested the significance of catalyst PEG400 and solvent glacial acetic acid at 5 h reaction. The optimum reaction conditions suggested by the RSM were the use of PEG400 (10.61 mol%) and glacial acetic acid (10.71 mL) for 5 h cycloocondensation. The experimental yield of 4,5-diphenyl-2-nitrophenyl-1H-imidazole (97%) was in agreement with predicted yield (97.5%).     

Potassium dihydrogen phosphate catalyzed one-pot synthesis of 2,4,5-triaryl-1H-imidazoles

<正>A simple and efficient method has been developed;benzil/benzoin undergoes smooth condensation with various substituted aldehyde and ammonium acetate in the presence of potassium dihydrogen phosphate(KH_2PO_4) under mild reaction conditions to afford the corresponding trisubstituted imidazole in excellent yields.The method for synthesis of product,the reaction mixture was reflux in ethanol for 40-90 min.The present method is simple,efficient,and cost-effective.     

Novel structural analogs of glyphosate based on azoles. 2*. N-Substituted imidazoles and pyrazoles obtained by alkylation of heterocycles containing carboxyl or phosphoryl groups in the ring

Alkylation of 4(5)-substituted 1H-imidazoles using the corresponding reagents gave imidazole 1,4-isomers containing phosphoryl and carboxyl groups together in the ring and in the alkyl fragment. The alkylation of pyrazoles containing a carboxyl group at positions 3(5) and 4 of the ring using diethyl phosphonomethyltriflate has been studied.     

Synthesis of Substituted 2-Azolyl-1-pyridylethan-1-ols

Through the reaction of (2-aryloxiran-2-yl)pyridines with triazole or imidazole a series of novel 2-azolyl-1-pyridylethan-1-ols has been synthesized with different positioning of the nitrogen atom in the pyridine fragment for pharmacological and agrochemical screening. The compounds prepared showed high fungicidal activity.     

Synthesis of (Z)-N-alkenyl-β-arylselanyl imidazoles via additive-free nucleophilic addition of imidazole to arylselanylalkynes

We present herein our results on the nucleophilic addition of imidazole to a range of arylselanylalkynes by simple heating in DMF without any additives to give (Z)-1-(1-organyl-(2-arylselanyl)vinyl)-1H-imidazoles. The reactions were performed under mild conditions with a range of arylselanylalkynes in good yields and with high regio- and stereoselectivity to give the respective (Z)-arylselanyl alkene as the only isomer.     

Isolation and properties of the products of the covalent hydration of 4H-imidazoles

The neutralization of 5-hydroxy-4,4-dimethyl-2-imidazolinium chlorides yields in the free state the products of the covalent hydration of the corresponding 4H-imidazoles — 5-hydroxy-4, 4-dimethyl-2-imidazolines. On being heated, the compounds obtained undergo various transformations, depending on the presence and position of oxygen-containing functions: 5-hydroxy-2-imidazoline gives 2-acetylamino-2-methyl-1-phenylpropan-1-ol; 3,5-dihydroxy-2-imidazoline dehydrates to 4H-imidazole 3-oxide; and 1,5-dihydroxy-2-imidazolines are converted into 2,3-dihydro-4H-1,2,5-oxadiazines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1087–1092, August, 1973.     

Convenient and Regiospecific Method for Synthesis of 4,5-Diaryl-1-methyl-2-(methylthio)-1H-imidazole

A convenient, high-yielding, regiospecific synthesis of 1H-imidazole-2-thiones ring has been developed. In addition, a series of 4,5-diaryl-1-methyl-2-(methylthio)-1H-imidazoles 8 were synthesized and characterized. The structure of regioisomers was confirmed through nuclear Overhauser effect spectroscopy and NMR spectroscopy.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Synthesis of azepino[1,2-<Emphasis Type="Italic">a</Emphasis>]benzimidazoles and imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]azepines

Fusion of 4-bromo-1,3-diphenyl-2-buten-1-ones (γ-bromodypnones) with 1,2-dimethyl-1H-benzimidazole and further treatment of the reaction product with a base (morpholine) gives 7,9-diaryl-5-methyl5,10-dihydroazepino[1,2-a]benzimidazol-11-ium bromides. The reaction of γ-bromodypnone with 1-alkyl-2-methyl-1H-imidazoles in benzene at 25 °C gives quaternary azolium salts. Upon heating their solutions in alcohol in the presence of K₂CO₃ the latter cyclize to 1-R-6,8-diaryl-1,5-dihydroimidazo[1,2-a]azepin-4-ium bromides or 1-R-6,8-diaryl-1H-imidazo[1,2-a]azepines depending on the nature of the substituent in the benzene rings and the substituent at the N(1) atom of the imidazole.     

某些1-酰基苯并咪唑及1-酰基咪唑衍生物的合成

2-取代的苯氧甲基苯并咪唑、咪唑分别与酰氯在缚酸剂存在下反应,制备了24个新的1-酰基2-苯氧甲基苯并咪唑及1-苯氧乙酰咪唑衍生物.后者容易吸水,转变成相应的铵盐.所制得的化合物中某些经小麦垂直生长法测定表现出一定的促进或抑制生长活性.     

Structural studies and photochromism of mercury(II)-iodo complexes of (arylazo)imidazoles

Neat reaction between HgI2 and 1-methyl-2-(phenylazo)imidazole (Pai-Me) under microwave irradiation has isolated a novel compound whose structure shows intercalated HgI2 in the layers of Pai-Me. They exist independently in interpenetrated arrays. In a solution phase study, the same reaction has synthesized an iodo-bridged azoimidazole-Hg(II) complex, [Hg(RaaiR')(mu-I)(I)]2 (RaaiR' = 1-alkyl-2-(arylazo)imidazole). The structures have been characterized by X-ray diffraction studies. Chloro-bridged Hg(II) complexes of azoimidazoles, [Hg(RaaiR')(mu-Cl)(Cl)]2, are also known. These complexes upon irradiation with UV light show trans-to-cis isomerization. The reverse transformation, cis-to-trans isomerization, is very slow with visible light irradiation. Quantum yields (phi t-->c) of trans-to-cis isomerization are calculated, and the free ligand shows higher phi than their Hg(II) complexes. The cis-to-trans isomerization is a thermally induced process. The activation energy (Ea) of cis-to-trans isomerization is calculated by controlled temperature reaction. The Ea's of free ligands are much higher than that of halo-bridged Hg(II)-azoimidazole complexes. Chloro-bridged Hg(II) complexes show lower Ea's than those of iodo-bridged complexes. DFT calculation has been adopted to rationalize the experimental results.     

Imidazole-Catalyzed Henry Reactions in Aqueous Medium

2-Nitroalkanols can be efficiently synthesized using imidazole as a mild Lewis basic catalyst in aqueous medium as well as in organic solvents. The products have been found in good yields without purification (> 95% purity by ¹H NMR) for aromatic aldehydes. Additionally, the very mild reaction conditions prevent the particular side reactions such as aldol condensation, Cannizzaro reaction, or dehydration of the 2-nitro alcohols into nitro alkenes even if aromatic aldehydes are used. This report satisfies the criteria for green synthesis in terms of reaction medium and recycling of the catalyst (imidazole).     

Microwave parallel library generation: comparison of a conventional- and microwave-generated substituted 4(5)-sulfanyl-1H-imidazole library

A methodology for the microwave parallel synthesis of libraries is described. The procedure involves the use of an array of expandable reaction vessels, which can accommodate pressure buildup within the vessel due to heating without loss of volatile solvents or reagents. A demonstration 24-membered library of substituted 4(5)-sulfanyl-1H-imidazoles was generated by both conventional and microwave procedures, achieving a reduction from 12 h to 16 min in library generation time for the microwave approach.     

Microwave assisted,sequential two-step,one-pot synthesis of novel imidazo[1,2-a]pyrimidine containing tri/tetrasubstituted imidazole derivatives

A series of novel imidazo[1,2- a ]pyrimidine containing tri/tetrasubstituted imidazole derivatives (1-10) has been synthesized via sequential two-step, one-pot, multicomponent reaction using imidazo[1,2- a ]pyrimidine-2-carbaldehyde, benzil, primary amines, and ammonium acetate catalyzed by p -toluenesulfonic acid under microwave-assisted conditions. The results showed that target compounds can be obtained from a wide range of primary amines bearing different functional groups with moderate to good yields (46%-80%) under optimum reaction conditions. This method provides a green protocol for imidazo[1,2- a ]pyrimidine containing tri/tetrasubstituted imidazole derivatives due to ethyl alcohol as a green solvent, microwave irradiation as a greener heating method and one-pot multicomponent reaction as a green technique. The synthesized compounds have been elucidated using various spectroscopic tools such as FT-IR, ¹H NMR, ¹³ C NMR, and MS.