I2/PhI(OAc)2-assisted oxidative C[sbnd]H amination protocols toward metal-free pragmatic synthesis of pyrrolo[2,3-b]indoles

Abstract

We report herein an I 2 /PhI(OAc) 2 catalytic system for the pragmatic construction of C-N bonds through C-H/N-H oxidative coupling protocol. Divergent pyrrolo[2,3- b ]indoles were efficiently prepared via I 2 -catalyzed intramolecular C–H amination reactions from ( E / Z )-2-indolylenamines under metal-free conditions. Various functional groups are tolerated under mild reaction conditions and the resulting pyrrolo[2,3- b ]indoles were obtained with mostly good to excellent yields. It was interesting to observe that both the ( E )- and ( Z )-isomers of the starting materials were efficiently transformed into the targeted product. The I + -mediated catalytic cycle was proposed based on mechanistic studies for this reaction. Both the ( E )- and ( Z )-isomers of the 2-indolylenamides were efficiently transformed into the same targeted pyrrolo[2,3- b ]indole product through this I + -catalyzed oxidative C-H/N-H coupling protocol. This green and environmentally benign strategy should be potentially served as a pragmatic synthetic approach for the late-stage modification of Pyrroindomycin analogues.