Palladium-Catalyzed Carbonylative Annulation of o-Alkynylphenols: Syntheses of 2-Substituted-3-aroyl-benzo[b]furans

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Abstract
We report here a general synthetic methodology for palladium-catalyzed carbonylative annulation of o-alkynylphenol to construct 2-substituted-3-aroyl-benzo[b]furan. On the basis of the results, this methodology could be applied to a wider selection of iodide substrates to generate desired products. In accordance with mechanistic studies, this process involves coordination of cationic and less hindered acyl palladium complexes with o-alkynylphenols to create a desired cascade triad (coordination, nucleophilic addition, and reductive elimination). Consistent with this mechanism, addition of 1 equiv of AgBF4 to palladium catalyst Pd(Ph3P)4 generates an ideal candidate for this unique transformation.