Coordination compounds of imidazoles with rhodium halides

Summary Compounds of the types [RhL₆](BF₄)₃, [RhL₅X](BF₄)₂ (L=1-methylimidazole), [RhL₄X₂]X (L=1-methylimidazole, 1-nbutylimidazole, 1-vinylimidazole, 1-vinyl-2-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-ethyl-4(5)-methylimidazole; X=Cl or Br) and [RhL₄X₂]BF₄ (L = 1-n-butylimidazole, 1-vinylimidazole, 1-vinyl-2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole and 1,2-dimethylimidazole) have been prepared and characterized by conductivity measurements, i.r. and¹H n.m.r. spectral studies. Analytical data agree with the monodentate nature of the ligands while a strongv(Rh-X) frequency reveals that the halogens aretrans to each other. The compounds also reveal d-d transition bands atca. 24000–22000 cm^–1 in the visible region.     

Thermal condensation of substituted imidazoles with trifluoroacetaldehyde

The title condensation provides the corresponding (1′-hydroxy-2′,2′,2′-trifluoroethyl)imidazoles in yields dependent on the electronic nature of the substituent: ortho-para directors promote the reaction while meta directors retard it strongly. 1-Alkylimidazoles gave only 2-adducts. 2-Substituted imidazoles yielded 4(5)-adducts together with small amounts of 4,5-bis-adducts. 4(5)-Substituted imidazoles provided 5(4)-adducts as the main products together with 2-adducts and 2,5(4)-bis-adducts.     

Mass spectra of some substituted imidazoles

Comparison of fragmentation pathways and high resolution measurements has revealed that the molecular ions of 1-(2-hydroxy-2-phenylethyl)imidazoles undergo elimination of benzaldehyde. The parent ions of trans-1-styrylimidazoles also cyclise in a manner similar to their photochemical reactivity. A rearrangement involving OH or OMe transfer between the trans-1-styryl and 5-acid or 5-methyl ester group of an imidazole is also described.     

Synthesis of substituted imidazoles via organocatalysis

A one-pot synthesis of substituted imidazoles is described. The cornerstone of this methodology involves the thiazolium-catalyzed addition of an aldehyde to an acyl imine to generate the corresponding alpha-ketoamide in situ followed by ring closure to the imidazole in a one-pot sequence. The extension of this methodology to the one-pot synthesis of substituted oxazoles and thiazoles is also described. [reaction: see text]     

N-alkylation products of substituted imidazoles and dihydropyrimidinediones with dibromoalkanes

The reactions of N-containing heterocycles with dihaloalkanes were studied. All structures were determined by NMR and mass techniques. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 31–34, January, 2007.     

Compounds of imidazoles with ruthenium(III) chloride

Summary Reaction of ruthenium(III) chloride with imidazole(Im) and different substituted imidazoles,viz. N-methylimidazole (N-MeIm), 2-methylimidazole(2-MeIm), 4-methylimidazole (4-MeIm),N-vinylimidazole(N-VIm), 2-methyl- 1-vinyl-imidazole(2-Me-1-VIm), 1,2-dimethylimidazole(1,2-Me,Im), 2-ethylimidazole(2-EtIm) and 2-ethyl-4(5)-methylimidazole (2-Et-4(5)-MeIm] yield products of the types [Ru₂L₄Cl₆] · 2 H₂O (L = N-VIm or 4-MeIm), [Ru₂L₄Cl₆] · 4 H₂O (L = Im or 2-Et-4(5)-MeIm), [Ru₂L ³ (H₂O)Cl₆] (L =N-MeIm or 2-MeIm), [Ru₂L ² (H₂O)₂Cl₆] (L = 1,2-Me₂Im or 4-MeIm), [Ru(2-Me-1-VIm)₃Cl₃] · H₂O and [Ru(2-EtIm)₃(H₂O)Cl₂]. These compounds were characterised by elemental analyses, conductometric measurements, i.r. and electronic spectral analyses. Magnetic moments range from 1.01 to 1.9 B.M. The e.s.r. spectra and g values of some of the compounds are indicative of high distortion.     

Expedient synthesis of substituted imidazoles from nitriles

Expedient and practical new methodology for the synthesis of substituted imidazoles was developed to provide a rapid access to a variety of 2-substituted, 1,2-disubstituted and 1,2,4-trisubstituted imidazoles by the direct CuCl-mediated reaction of nitriles with α-amino acetals in an intermolecular as well as intramolecular fashion.     

Reaction of hydrazonoyl halides with N-aryl substituted benzamidines

The reaction between hydrazonoyl halides and N-arylbenzamidines leads to the simultaneous formation of products derived from a substitution and a cycloaddition reaction via two independent paths.     

Cross-coupling reactions of arylsilanols with substituted aryl halides

[reaction: see text] The palladium-catalyzed cross-coupling of arylsilanols with aryl iodides and aryl bromides (in the presence of cesium carbonate) furnished various biaryl products in high yield. An extensive series of optimizations led to the identification of key variables, including activator, solvent, catalyst, and hydration level, that influence the rate and selectivity of the process. Manipulation of these features provided an effective coupling method of wide scope and generality.     

A novel synthesis for new substituted imidazoles

The addition of dimethyl acethylendicarboxylate (DMAD) to thiosemicarbazone and guanylhydrazone of aldehydes afforded compoundes which were characterized to be new substituted imidazoles. Their structures were determined by ¹H NMR, IR, mass spectra and elemental analyses.     

Copper oxide nanoparticles catalyzed vinylation of imidazoles with vinyl halides under ligand-free conditions

Recyclable copper oxide nanoparticles catalyzed most efficient and straightforward protocol for the vinylation of imidazoles with vinyl halides under ligand-free conditions. Utilizing this protocol various imidazoles were cross-coupled with different substituted vinyl halides to get the corresponding products in excellent yields with the retention configuration.     

Syntheses of substituted pyrrolo[2,3-d]imidazoles

Starting from the readily available 5-hydroxymethyl-2-mercapto-1-methylimidazole (1) substituted pyrrolo[2,3-d]imidazoles were prepared.     

Selective complexation of palladium and osmium with substituted pyrimidinethiols

1-Amino-, 1-anilino- and 1-(2',4'-dinitroanilino)-4,4,6-trimethyl-1H,4H-2-pyrimidinethiols react with Pd(II) and Os(VIII), forming coloured complexes extractable into non-polar organic solvents. The optimum conditions for the complexation have been established. Beer's law is obeyed and by an extractive spectrophotometric procedure, microgram quantities of the two metals are determined in the presence of large amounts of diverse ions, including all the other metals of the iron and platinum groups.     

Palladium-catalyzed cross-coupling reactions of 2-indolyldimethylsilanols with substituted aryl halides

[reaction: see text] A mild and general cross-coupling reaction of 2-indolylsilanols has been developed. The experimental variables that lead to successful coupling are (1) the use of sodium tert-butoxide as the activator, (2) the use of copper(I) iodide in stoichiometric quantities, and (3) the use of Pd2(dba)3.CHCl3 as the catalyst. Under these conditions N-(Boc)-2-indolyldimethylsilanol reacts with a variety of aromatic iodides to afford the coupling products in good yield (70-84%).     

Structural characterization of methanol substituted lanthanum halides

The first study into the alcohol solvation of lanthanum halide [LaX₃] derivatives as a means to lower the processing temperature for the production of the LaBr₃ scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H₂O)₇](Br)₂}₂ (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H₂O)₇(MeOH)₂](Br)₃ (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH₂, crystals of [Ca(MeOH)₆](Br)₂ (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr_2.75·5.25(MeOH)]^+0.25 [LaBr_3.25·4.75(MeOH)]^−0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr₃ in MeOH forming the 8-coordinated [LaBr₃(MeOH)₅] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX₃ derivatives were isolated as [(MeOH)₄(Cl)₂La(μ-Cl)]₂ (6) and [La(MeOH)₉](I)₃·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (¹³⁹La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4–6 were slightly higher in comparison to their hydrated counterparts.     

Novel and convenient routes to substituted pyrroles and imidazoles

S-Melhyl N-(benzotriazol-1-ylmethyl)thioimidate 6 is obtained by lithiation of the corresponding N-(benzotriazol-1-ylmelhyl) thioamide 5 and subsequent reaction with methyl iodide. Derivative 6 undergoes [2 + 3] cycloaddition reactions with ,β-unsaturated -esters, -ketones and -nitriles, and vinylpyridines which are followed by elimination of benzotriazole and the thioalkoxy group, to give 2,3,4-trisubstituted pyrroles. Lithiaiion of 6 followed by reactions with imines gives cyclized 4,5-dihydroimidazoles 14 which upon further treatment with ZnBr₂ or direct refluxing in toluene yield the 1,25-trisubstituted imidazoles 15 in good yields.     

Benzotriazole: an excellent ligand for Cu-catalyzed N-arylation of imidazoles with aryl and heteroaryl halides

Benzotriazole (BtH) is an efficient ligand for the Cu-catalyzed N-arylation of imidazoles with aryl and heteroaryl halides. A combination of CuI/BtH was found to be an efficient and inexpensive catalyst system to carry out the N-arylation of imidazoles affording the corresponding products in good to excellent yields.     

Reaction of combination of trimethylvinylsilane with organic halides catalyzed by palladium derivatives

Conclusions It has been discovered that halopyridines, halonaphthalene, iodocarborane, and aryl iodides are vinylated by a reaction of trimethylvinylsilane, catalyzed by palladium complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2342–2343, October, 1984.We wish to express our gratitude to E. I. Mysov for taking the chromato-mass spectra.