The direct dearomative addition of arenes to the C3 position of unprotected indoles is reported under operationally simple conditions, using triflic acid at room temperature. The present regioselective hydroarylation is a straightforward manner to generate an electrophilic indole at the C3 position from unbiased indoles in sharp contrast to previous strategies. This atom-economical method delivers biologically relevant 3-arylindolines and 3,3-spiroindolines in high yields and regioselectivities from both intra- and intermolecular processes. DFT computations suggest the stabilization of cationic or dicationic intermediates with H-bonded (TfOH)n clusters.
Keywords: Dearomatization; Indoles; Indolines; Super Acids; Umpolung.
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