Indium(III)-catalyzed synthesis of benzo[b]furans by intramolecular hydroalkoxylation of ortho-alkynylphenols: scope and mechanistic insights.

Alonso-Marañón, L.; Martínez, M. M.; Sarandeses, L. A.; Gómez-Bengoa, E.; Pérez Sestelo, J.


J. Org. Chem. 2018, 83, 7970–7980 (DOI: 10.1021/acs.joc.8b00829).

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Indium(III) halides catalyze the hydroalkoxylation reaction of ortho-alkynylphenols to aff ord benzo[b]furans in good yields. The reaction proceeds with 5-endo-dig regioselectivity with a variety of phenols functionalized at the arene and alkyne moieties in high yields using InI3 (5 mol%) in DCE. Experimental and computational studies support a mechanism based on the indium(III) p-Lewis acid activation of the alkyne followed by nucleophilic addition of the phenol and final protodemetalation to afford the corresponding benzo[b]furan. DFT calculations suggest that dimer In2I6 is the catalytic species through a novel double coordination with the alkyne and the hydroxyl group.