Trifluoroacetic Acid Catalyzed Cascade Reactions of 2,3‐Diketoesters with Cyclohexane‐1,3‐diones: Strategy Towards 4‐Hydroxybenzofuran Derivatives

Abstract

An efficient trifluoroacetic acid catalyzed cascade reaction of 2,3-diketoesters with cyclohexane-1,3-diones is described for the synthesis of a series of 4-hydroxybenzofurans. This simple protocol has the advantages of easy operation, readily available starting materials, good functional group tolerance, and easily scale-up. Subsequent derivatization of the 4-hydroxybenzofurans provides a reasonable route to access highly functionalized benzofurans.

Permanganate oxidation of α,β-unsaturated carbonyls to vicinal tricarbonyls

“…As a result, VTCs are highly reactive and can be used as useful synthons. 1,2 A series of carbo- and heterocyclic compounds can be obtained from VTCs, such as cyclopentane, 3 furan, 4 benzofuran, 5 pyrrole, 6 indole, 7 imidazole, 8 isoquinoline, 9 and quinoxaline. 10 VTCs have also been reported in the total synthesis of natural products.…”

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 …”