Rhodium(III)‐Catalyzed Oxidative Annulation of Amidines with Alkynes via Sequential C−H Bond Activation

In this paper, a rhodium‐catalyzed sequential two‐fold ortho‐C−H functionalization of N‐phenylbenzimidamide with internal alkyne is reported. The double C−H activations proved viable in a one‐pot fashion with the assistance of C=N and C−N bonds, providing a series of benzimidazoisoquinolines with high levels of positional selectivity control. The operationally simple transformation showed high functional group compatibility and featured the cleavage of C−H bonds located on different a moiety of the N‐phenylbenzimidamide substrates. Detailed mechanistic studies provided strong support for C−H bond cleavage on the N‐phenyl ring to be preferential compared with C−H bond cleavage on C‐phenyl ring. As a multifunctional catalytic platform, the rhodium catalyst conducted two independent and compatible catalytic cycles in one pot. The first rhodium‐catalyzed oxidative double C−H activation/annulation reaction of amidines and alkynes to construct benzimidazoisoquinolines was developed. The operationally simple transformation showed high functional group compatibility and featured the cleavage of the C−H bonds located on a different moiety of the N‐phenylbenzimidamide substrates.