N-Arylimidazole synthesis by cross-cycloaddition of isocyanides using a novel catalytic system

A direct catalytic synthesis of N-arylimidazoles starting from the corresponding N-arylformamides and N-formylglycine esters is described. Application to different aryl substituted electron-withdrawing and -donating groups provided the analogous heterocyclic compounds in very high yields. The use of copper(I) oxide/proline catalysts allowed the reactions to proceed at room temperature. The first synthesis of N-arylimidazole bearing carbohydrate moieties is also described.     

The copper-catalyzed cross-coupling reactions of aryl diazonium salts and isocyanides

The copper-catalyzed cross-coupling reaction of aryl diazonium salts and isocyanides has been performed. This is a successful example of preparation of arylcarboxyamides with moderate to good yield under mild conditions.     

Synthesis of glycosyl isocyanides

Substitution of benzylated or methylated glycopyranosyl and furanosyl bromides with silver cyanide gives rise to glycosylisocyanides as main products. The isocyanide structure is ascertained by physical (¹³C NMR, IR) and by chemical methods (hydrolysis, isomerisation to nitriles).     

Synthesis of imidazoles

Conclusions The synthesis of 4-alkylimidazoles was carried out by heating (2-oxoalkyl)triethylammonium bromides with formamide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No, 1, pp. 140–143, January, 1989.     

Synthesis of imidazoles

Silica gel was found to facilitate the conversion of 3-bromo-2-alkanones to imidazoles by the action of formamide. The selective 3-bromination of 2-alkanones was carried out in ethyl acetate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 511–513, February, 1991.     

Synthesis of indole derivatives via isocyanides

Fast and convenient approaches to the indole nucleus from isocyanides are reviewed as a means for the tailored preparation of conveniently functionalized indoles by using the unique reactivity of isocyanides in one-pot multicomponent and cascade reactions.     

Synthesis of diaryl ethers through the copper-catalyzed arylation of phenols with aryl halides using microwave heating

The copper-catalyzed arylation of phenols with a variety of aryl halides using microwave heating is described.     

Synthesis of tri- and tetrasubstituted imidazoles

A reliable sequence that allows for regiospecific incorporation of four alkyl substituents on an imidazole ring has been developed. This procedure involves the addition of a substituted amino alcohol to a thioamide and subsequent oxidation with PDC. Unlike many imidazole syntheses, acid-sensitive functionality is tolerated given the mild conditions.     

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]     

Synthesis and properties of alkylated imidazoles

Alkylation of 4(5)-nitroimidazole-5(4)-sulfonamide with benzyl bromide occurred on both ring nitrogens. The structures of the products could be assigned by comparison of the chemical shifts of the sulfonamide hydrogens in the nmr spectra with those of the isomeric methyl derivatives, which were prepared by differing routes. Uv and nmr spectral data are reported for a number of bromo-, nitro-, mercapto-, sulfamyl- and amino- substituted imidazoles as well as for both of the isomeric methylated derivatives of the series.     

Efficient use of a surfactant for copper-catalyzed coupling reaction of arylboronic acids with imidazoles in water

Copper-catalyzed oxidative coupling of arylboronic acids with imidazoles in water was realized by using an amphiphilic surfactant. By choosing an appropriate surfactant, reactions of a variety of arylboronic acids proceeded smoothly under mild and base-free conditions, providing an efficient, practical, and greener method for the synthesis of N-arylimidazoles.     

Synthesis of two closely spaced cysteine barbiturates containing peptides by copper-catalyzed oxidation of contryphan disulfide

In this report, we are documenting the synthesis of peptide barbiturate through copper-catalyzed oxidation of peptide disulfide. Single disulfide-containing contryphans are used as models to access possibility of anchoring of barbituric acid (BRB) onto the peptide disulfide. Current method permits anchoring of two molecules of BRB onto the polypeptide and yield of peptide barbiturates varies from 59 to 84%. Formation of cysteine sulfenic acid (Cys-SOH) during oxidation of disulfide was confirmed using chemical probe of Cys-SOH dimedone. Mass spectrometric studies have confirmed the presence of cysteine barbiturate in anchored peptides. Based on the nature of reactive oxygen species involved in oxidation of peptide disulfide, possible mechanisms were proposed for anchoring of BRB onto the peptide disulfide through Cys-SOH. This is the first report on anchoring of two molecules of BRB onto the closely spaced cysteine residues of single polypeptide.     

Postsynthetic DNA modification through the copper-catalyzed azide-alkyne cycloaddition reaction

The attachment of labels onto DNA is of utmost importance in many areas of biomedical research and is valuable in the construction of DNA-based functional nanomaterials. The copper(I)-catalyzed Huisgen cycloaddition of azides and alkynes (CuAAC) has recently been added to the repertoire of DNA labeling methods, thus allowing the virtually unlimited functionalization of both small synthetic oligonucleotides and large gene fragments with unprecedented efficiency. The CuAAC reaction yields the labeled polynucleotides in very high purity after a simple precipitation step. The reviewed technology is currently changing the way in which functionalized DNA strands are generated cost-efficiently in high quality for their application in molecular diagnostics systems and nanotechnological research.     

Synthesis of optically active bifunctional building blocks through enantioselective copper-catalyzed allylic alkylation using Grignard reagents

Enantioselective copper-catalyzed allylic alkylations were performed on allylic bromides with a protected hydroxyl or amine functional group using several Grignard reagents and Taniaphos L1 as a ligand. The terminal olefin moiety in the products was transformed into various functional groups without racemization, providing facile access to a variety of versatile bifunctional chiral building blocks.     

Synthesis of 1,4-diarylsubstituted 1,3-diynes through ligand-free copper-catalyzed oxidative decarboxylative homocoupling of aryl propiolic acids

An efficient method of ligand-free Cu-catalyzed oxidative decarboxylative homocoupling of aryl propiolic acids was developed. When CuI was employed as the catalyst and I₂ as the oxidant, the decarboxylative homocoupling reaction for C_sp–C_sp bond formation in DMSO underwent smoothly to afford the corresponding 1,4-disubstituted 1,3-dialkynes in good to excellent yields without any organic ligands. This catalytic system was applicable to aryl propiolic acids bearing different steric, electronic, and functional groups.     

Tetrazole-1-acetic acid as a ligand for copper-catalyzed N-arylation of imidazoles with aryl iodides under mild conditions

Tetrazole-1-acetic acid was found to serve as a superior ligand for CuI-catalyzed N-arylation of imidazoles with aryl iodides under a low catalyst loading (5 mol% of CuI). A variety of aryl iodides could be aminated to provide the N-arylated products in good to excellent yields without the need of an inert atmosphere.     

An efficient synthesis of chlorinated imidazoles through tert-butyldimethylsilyloxy derivatives

The protection of 2-substituted imidazole-5-methanol derivatives by tert-BDMS allowed the chlorination of the heterocycle in position 4 with good yield whereas direct chlorination on the imidazole alcohol was unsuccessful.