New reductive rearrangement of N-Arylindoles triggered by the Grubbs-Stoltz reagent Et3SiH/KOtBu

Smith, Andrew J. and Dimitrova, Daniela and Arokianathar, Jude N. and Kolodziejczak, Krystian and Young, Allan and Allison, Mark and Poole, Darren L. and Leach, Stuart G. and Parkinson, John A. and Tuttle, Tell and Murphy, John A. (2020) New reductive rearrangement of N-Arylindoles triggered by the Grubbs-Stoltz reagent Et3SiH/KOtBu. Chemical Science, 11 (14). pp. 3719-3726. ISSN 2041-6520 (https://doi.org/10.1039/D0SC00361A)

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Abstract

N-Arylindoles are transformed into dihydroacridines in a new type of rearrangement, through heating with triethylsilane and potassium tert-butoxide. Studies indicate that the pathway involves (i) the formation of indole radical anions followed by fragmentation of the indole C2-N bond, and (ii) a ring-closing reaction that follows a potassium-ion dependent hydrogen atom transfer step. Unexpected behaviors of ‘radical-trap’ substrates prove very helpful in framing the proposed mechanism