Transition-Metal-Free Transfer Hydrogenative Cascade Reaction of Nitroarenes with Amines/Alcohols: Redox-Economical Access to Benzimidazoles

This
report describes an efficient transition-metal-free process
toward the transfer hydrogenative cascade reaction between nitroarenes
and amines or alcohols. The developed redox-economical approach was
realized using a combination of KOtBu
and Et3SiH as reagents, which allows the synthesis of benzimidazole
derivatives via σ-bond metathesis. The reaction conditions hold
well over a wide range of substrates embedded with diverse functional
groups to deliver the desired products in good to excellent yields.
The mechanistic proposal has been depicted on the basis of a series
of control experiments, mass spectroscopic evidence which is well
supported by density functional theory (DFT) calculations with a feasible
energy profile.