Imidazole 2-amido

This method accommodates aryl aldehydes with both electron-deficient and electron-rich aryl substitutents. Acetaldehyde is also a competent couphng partner, providing the corresponding amido ketone in 62% yield. Acyl substitution of the tosyl amide varies to include hydrogen, methyl, tert-butoxy, and phenyl producing the desired a-amido ketones in moderate to high yields. Expansion of this methodology to synthesize di- and tri-substituted imidazoles was reported by Murry and co-workers (Scheme 7) [54]. 

Imidazolium ligands, in Rh complexes, 7, 126 Imidazolium salts iridium binding, 7, 349 in silver(I) carbene synthesis, 2, 206 Imidazol-2-ylidene carbenes, with tungsten carbonyls, 5, 678 (Imidazol-2-ylidene)gold(I) complexes, preparation, 2, 289 Imidazopyridine, in trinuclear Ru and Os clusters, 6, 727 Imidazo[l,2-a]-pyridines, iodo-substituted, in Grignard reagent preparation, 9, 37—38 Imido alkyl complexes, with tantalum, 5, 118—120 Imido-amido half-sandwich compounds, with tantalum, 5,183 /13-Imido clusters, with trinuclear Ru clusters, 6, 733 Imido complexes with bis-Gp Ti, 4, 579 with monoalkyl Ti(IV), 4, 336 with mono-Gp Ti(IV), 4, 419 with Ru half-sandwiches, 6, 519—520 with tantalum, 5, 110 with titanium(IV) dialkyls, 4, 352 with titanocenes, 4, 566 with tungsten... 

Recently, some interesting photochemical reactions of 2,5-dimethyl-and 2,5-diphenylpyrazine 1-oxide have been reported. Irradiation of a nitrogen-stirred benzene suspension of 2,5-dimethylpyrazine 1-oxide gives 5% 2-acetyl-4-methylimidazole (220) and 15% 2,4-dimethyl -imidazole (221). When the irradiation is carried out in aqueous solution, 10% 2-hydroxy 3,0-dimethylpyrazine (126) and 20% 1-acet-amido-2-formamido-l-propene (222) is formed. The mechanisms in Scheme 49 are suggested for these transformations. 

Imidazoles can be made by 1,5-dipolar cyclization of suitable 2-azavinamidinium salts [6. 7]. Such salts (10) are readily made from amidines (or guanidines) and amido or ureido chlorides (9), and in the presence of sodamide in liquid ammonia they cyclize to form electron-rich imidazoles... 

Imidazoles.—Formation. Several new syntheses of imidazoles from isocyanides have been reported these include the formation of 1-alkyl-imidazoles (396) by the action of primary amines on 2-isocyano-2-tosylstyrene, PhCH=C-(NOTos, the cyclization of the enamine Me2NCH=C(NC)C02Me to compound (397) in the presence of methyl iodide,and the preparation of the ethers or thioethers (398) from isocyano-cyanides R CH(NC)CN by their reaction with alcohols or thiols R XH, respectively.Aromatic aldehydes are converted into 2-aryl-4,5-dichloroimidazoles (399) by the combined action of cyanogen and hydrochloric acid. 5-Acetyl-4-methylimidazole (400) results when form-amido-acetylacetone, AC2CHNHCHO, is heated with formamide and formic acid. Exhaustive chlorination of tetramethyldithio-oxamide leads to the tri-chloro-imidazolium cation (401). ... 

From a disconnection perspective, the use of a-amido ketones is appealing for many functionalized imidazoles. However, it sometimes suffers from many steps and poor overall yields. Much development work has gone into the preparation of the amido-ketone. For example, the Merck group has published the preparation of substrates for cyclization using a Stetter-like multicomponent coupling reaction (MCR). ... 

After the excellent development work on the process to prepare the a-amido-ketone, the work was further stretched into the one-pot synthesis of imidazole. This method proved somewhat general and gave good yields of many 4,5-di-substituted imidazoles. ... 

N-benzoylglycinate esters occurs when there is a good leaving group as in phenyl esters (Williams, 1975). Acetylimidazole is more reactive than phenyl acetate (Oakenfull and Jencks, 1971) and so displacement of the imidazole by the intramolecular amido group is expected. 

Scheme 21 Imidazole-imine C-C coupling and protonation of the resulting amido group to afford cationic amino complexes.

Proteins are built up of a-aminoacids differing in the presence of reactive groups such as amino, carboxyl, amido, hydroxyl, thiol and imidazole groups. The structure of proteins is an extended chain of aminoacid residues joined by amide linkages which are readily degraded by enzymes, particularly proteases. 

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