Bromine radical enhanced stoichiometric pyridylation of alkylarenes and diarylmethanes at room temperature

Abstract

The radical–radical couplings of readily available alkylarenes and diarylmethanes with cheap and abundant 4-cyanopyridine in a stoichiometric manner at room temperature have been developed. This method employed broadly applicable petroleum-derived toluene derivatives as latent alkylating reagents, promoted by the merger of photoredox catalysis and hydrogen atom transfer catalysis. A wide range of diarylmethanes and triarylmethanes with heteroaryl groups were synthesized in good to excellent yields. Given the stoichiometric and mild conditions, the pyridine moiety was also successfully introduced into bioactive molecules and complex compounds. Mechanistic investigations reveal that the bromine radical serves as a selective hydrogen atom transfer (HAT) reagent to rapidly abstract a hydrogen atom from benzyl C–H bonds.