Nucleophilic aromatic substitution, followed by subsequent 5-endo-dig cyclization between the nucleophile and an ortho acetylene effectively furnished benzofurans and 2-substituted indoles. The acetylene serves both the role of electron withdrawing group to activate the substrate for SNAr, and the C1-C2 carbon scaffold for the newly formed 5-membered heteroaromatic ring. This method allows for the bond forming sequence of Ar-X – N/O – C1 to proceed in a single synthetic step, providing indoles and benzofurans in moderate to high yields. Brominated and chlorinated substrates are tolerated, because the method is not transition-metal mediated. Benzofuran formation can be conducted using water or water/DMSO mixtures as solvent.

Acetylene-activated SNAr/intramolecular cascade sequence for the synthesis of indoles, benzofurans, and related heterocycles in water or DMSO

250th National Meeting (2015)

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