Accessing a Biologically Relevant Benzofuran Skeleton by a One-Pot Tandem Heck Alkynylation/Cyclization Reaction Using Well-Defined Palladium N-Heterocyclic Carbene Complexes
| Autor: | A. P. Prakasham, Darshan S. Mhatre, Anuj Kumar, Manoj Kumar Gangwar, Alok Ch. Kalita, Prasenjit Ghosh |
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| Přispěvatelé: | Supramolecular Chemistry & Catalysis |
| Rok vydání: | 2016 |
| Předmět: |
Models
Molecular Spectrometry Mass Electrospray Ionization Magnetic Resonance Spectroscopy Stereochemistry Alkyne chemistry.chemical_element Cooperativity 010402 general chemistry 01 natural sciences Mixed Aqueous-Medium Fluoride-Free Hiyama Catalysis Inorganic Chemistry chemistry.chemical_compound Themed Precatalysts Ligands Synthesis Heterocyclic Compounds Catalytic Application Pyridine Physical and Theoretical Chemistry Benzofuran Gold(I) Complexes Bimetallic strip Benzofurans chemistry.chemical_classification Straightforward Synthesis 010405 organic chemistry Combinatorial chemistry Transfer Hydrogenation 0104 chemical sciences chemistry Cyclization Alkynes Room-Temperature Methane Carbene Michael Reactions Palladium |
| Zdroj: | Inorganic Chemistry, 55(6), 2882-2893. American Chemical Society |
| ISSN: | 1520-510X 0020-1669 |
| Popis: | Well-defined palladium N-heterocyclic carbene (NHC) complexes were employed in the one-pot tandem Heck alkynylation/cyclization sequence for preparing biologically relevant benzofuran compounds under copper-free conditions in a time-efficient step-reduced fashion. In particular, a series of binuclear palladium complexes, 1b-1e and 2b-2e, of the alkyl-bridged NHC ligands, namely, {1,1'-di-R-1-4,4'-R-2-di-1,2,4-triazoline-5,5'-diylid-2-ene] (R-1 = i-Pr; R-2 = -(CH2)(2)-, -(CH2)(3)-), and their mononuclear analogues, trans-(NHC)PdBr2(pyridine) (3b) and cis-(NHC)-PdBr2(PPh3) (3c), successfully catalyzed the one-pot tandem Heck alkynylation/cyclization reaction of 2-iodophenol with a variety of terminal alkyne substrates, yielding 2-substituted benzofuran derivatives. The mononuclear complexes 3b and 3c were nearly half as active as the representative dinuclear analogue 1c under analogous reaction conditions, thereby implying that, at the same mole percent of the palladium loading, the monometallic 3b and 3c and the bimetallic 1c complexes were equally effective as catalysts. The two sites of the bimetallic complex 1c performed as two separate independent catalytic sites, displaying no cooperativity effect in the catalysis. Finally, the practical utility of the aforementioned catalysts was demonstrated for a representative catalyst 1c through the convenient synthesis of a key intermediate, 3-[2-(benzo[d][1,3]dioxol-5-yl)-7-methoxybenzofuran-5-yl]propan-1-ol, in a total-synthesis protocol of the natural product Egonol. |
| Databáze: | OpenAIRE |
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