Substituent Electronic Effects Govern Direct Intramolecular C–N Cyclization of N‑(Biphenyl)pyridin-2-amines Induced by Hypervalent Iodine(III) Reagents

The hypervalent iodine­(III) reagent-induced the direct intramolecular C–N cyclization of N-(biphenyl)­pyridin-2-amines to 6-arylbenzimidazoles and N-pyridinyl-9H-carbazoles is presented. The substituent electronic effects governing the formation of benzimidazoles and carbazoles from the reaction of N-(biphenyl)­pyridin-2-amines with hypervalent iodine­(III) reagents is investigated. Radical trapping and UV–vis spectroscopic experiments on the detection of the cation radical are carried out. Rational mechanisms for these reactions are presented. The selective intramolecular C–N and C–O cyclization of N-(biphenyl)­acetamides based on the substituent electronic effects is also presented.