New reductive rearrangement of <i>N</i>-arylindoles triggered by the Grubbs–Stoltz reagent Et₃SiH/KO^tBu

Abstract

<i>N</i>-Arylindoles are transformed into dihydroacridines in a new type of rearrangement, through heating with triethylsilane and potassium <i>tert-</i>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.