An efficient and mild synthesis of highly substituted imidazoles

Regioselective Base-induced Condensations of Acrylic Acid Derivatives

“…Cyclohexenone derivatives 9a,b were obtained on dilution and acidi¢cation of the reaction mixture of 8a,b, before the decarboxylation process. Reaction of 9a with hydrazine hydrate 9 a¡orded 6-aryl-3-oxo-2,4,5,3a-tetrahydro-1Hindazole-4-carboxylic acid (10a), which showed a n(NH) band at 3287 cm À1 and molecular ion at m/z 286. Treatment of 12b with malononitrile in the presence of triethylamine yielded the adduct 13b, which showed ng x bands at 2233 and 2217 cm À1 .…”

Some Synthetic Uses of Double‐Bonded Functional Groups

“…The reaction usually gives a stereocontrolled product in up to 60% yield (equation 200) 714 (200) Carboximidoyl chlorides may be reacted with oximes to give 30 65% yield of amidines, which may then be used to form imidazoles in good yields, by treatment with TsOH (equation 201) 716 . Highly substituted imidazoles may be prepared in a simple one-pot synthesis by treating vicinal tricarbonyl compounds with an aldehyde and ammonium acetate (equation 202) 717 . The reaction occurs in 66 90% yield and seems to be general in scope.…”

Gold(I)-Catalyzed Oxidation of Acyl Acetylenes to Vicinal Tricarbonyls

“…1,2 Owing to their highly electrophilic nature, VTCs demonstrate great reactivity toward even rather weak nucleophiles, and these additions were successfully applied for construction of various carbon−carbon and carbon− heteroatom bonds. All these transformations provide a wide range of carbo-and heterocyclic systems including, for example, cyclopentane, 3 furan, 4 pyrrole, 5 indole, 6,7 benzofuran, 8 imidazole, 9 pyrazine, 10 quinoxaline, 10 triazines, 11 and isoquinoline. 12 Several examples of applications of VTCs in the total synthesis of natural products have been reported.…”

“…Vicinal tricarbonyl compounds (VTCs) along with their hydrate forms have proven to be useful synthetic building blocks. , Owing to their highly electrophilic nature, VTCs demonstrate great reactivity toward even rather weak nucleophiles, and these additions were successfully applied for construction of various carbon–carbon and carbon–heteroatom bonds. All these transformations provide a wide range of carbo- and heterocyclic systems including, for example, cyclopentane, furan, pyrrole, indole, , benzofuran, imidazole, pyrazine, quinoxaline, triazines, and isoquinoline . Several examples of applications of VTCs in the total synthesis of natural products have been reported. , Furthermore, vicinal tricarbonyl amides (α,β-diketoamides) and their hemiketal forms were identified in biologically active natural macrolide compounds including elastase inhibitors and immunosuppressants such as rapamycin and tacrolimus …”