Umpolung of Indoles: Triflic Acid-Mediated C3-Regioselective Hy-droarylation of N-H Indoles

The direct dearomative addition of arenes to the C3-position of unprotected indoles is reported under operationally simple conditions with triflic acid at room temperature. The present regioselective hydroarylation is a straightforward manner to gen-erate an electrophilic indole at the C3-position without the need to introduce a deactivating acetyl group on the indolic nitrogen as in previously reported strategies. This atom economy method delivers biologically relevant 3-aryl indolines and 3,3-spiroindolines in high yields and regioselectivities from both intra and intermolecular processes.