A facile and efficient asymmetric dearomative oxyalkylation of indoles with TEMPO oxoammonium salt and a variety of aldehydes and ketones has been described. This metal-free approach provides a straightforward access to C2 quaternary oxindoles in high yields with excellent diastereoand enantioselectivities under very mild conditions. The reaction goes smoothly even with only 0.1% equivalent catalyst. Moreover, 2-alkylindoles have proven to be suitable substrates for the first time.

The oxidative, dearomative cross-dehydrogenative coupling of indoles with various C-H nucleophiles is developed. This process features a broad substrate scope with respect to both indoles and nucleophiles, affording structurally diverse 2,2-disubstituted indolin-3-ones in high yields (up to 99%). The oxidative dimerization and trimerization of indoles has also been demonstrated under the same conditions.

Described is an efficient oxidative dearomatization of indoles with TEMPO oxoammonium salt and a broad range of nucleophiles.

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