Radical-mediated selective cascade addition/annulation of ((2-isocyanophenyl)methylene)dibenzenes for the divergent synthesis of 3H-indoles and indolines

A radical-mediated selective cascade addition/annulation of ((2-isocyanophenyl)methylene)dibenzenes for the divergent synthesis of 3,3-diaryl-3 H -indoles and 2-alkyl-3,3-diarylindolines under transition metal-free conditions is presented. Diphenyl disulfide promotes the intramolecular annulation of isocyanides to provide 3,3-diaryl-3 H -indoles in the presence of TBHP, while tetra- butylammonium iodide (TBAI) facilitates the intermolecular alkylation/annulation reaction to yield 2-alkyl-3,3-diarylindolines in inexpensive, readily available ether solvent using DTBP as oxidant. It provides a sustainable and practical protocol for radical coupling of isocyanides with C(sp 3 ) moieties (alkyl). The possible mechanism may involve radical generation induced by peroxide, radical addition, 1,5-hydrogen atom transfer (HAT), and radical annulation sequence. A radical-mediated selective cascade addition/annulation of ((2-isocyanophenyl)methylene)dibenzenes for the divergent synthesis of 3,3-diaryl-3 H -indoles and 2-alkyl-3,3-diarylindolines under transition metal-free conditions is presented. It provides a sustainable and practical protocol for radical coupling of isocyanides with C(sp 3 ) moieties (alkyl).