A mild and convenient synthesis of carbazoles by TfOTMS (trimethylsilyl trifluoromethanesulfonate)-catalyzed ring-opening annulation of 2-amidodihydrofurans is presented with a high degree of chemoselectivity and regioselectivity. This procedure was also scaled up to a gram-scale synthesis. The reaction could involve an iminonium intermediate through a series of C-O, C-N bond cleavages, C-C bond formations, and a 1,2-migration process.
Keywords: acid-catalysis; carbazoles; chemoselectivity; regioselectivity; ring-opening annulation.
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