Metal-free electrochemical [3+2] heteroannulation of anilines with pyridines enabled by dual C-H radical aminations

An unprecedented metal-/external-oxidant-free electrochemical intermolecular [3 + 2] heteroannulation of anilines with electron-deficient pyridines enabled by dual C-H radical aminations for producing functionally diverse benzo[4,5]imidazo[1,2-a]pyridines is described. The site-selectivity of aminations of aryl C(sp(2))-H bonds relies on the electronic effect of two reaction partners: each contributed two reactive sites (a C(sp(2))-H bond and a nitrogen atom-based functional group) and the electron-withdrawing groups at the 4 position of the pyridine ring are crucial. Mechanistic studies show that this method sequence consists of the generation of the nitrogen-centered radical (NCR) and the pyridine radical anion, radical coupling and dual C-N aminations.

Automated summary

This method describes an unprecedented metal-/external-oxidant-free electrochemical intermolecular [3 + 2] heteroannulation of anilines with electron-deficient pyridines enabled by dual C-H radical aminations for producing functionally diverse benzo[4,5]imidazo[1,2-a]pyridines. The site-selectivity of aminations of aryl C(sp(2))-H bonds relies on the electronic effect of two reaction partners, with electron-withdrawing groups at the 4 position of the pyridine ring being crucial. Mechanistic studies show that the method sequence involves the generation of the nitrogen-centered radical (NCR), the pyridine radical anion, radical coupling, and dual C-N aminations.