Electrocatalytic oxidative C–H cycloamination towards tricyclic [1,2,4]triazolo-[3,4-i]purine nucleosides mediated by bromide ions

An environmentally benign electrochemical approach is presented to access a diversely functionalized [1,2,4]triazolo[3,4-i]purine heterocyclic framework. A bromide-mediated indirect oxidation strategy was utilized to promote intramolecular C(sp²)–H cycloamination with high efficiency and under mild metal- and oxidant-free conditions. The method exhibits a broad substrate scope, which is well manifested by nucleoside substrates with one or even three hydroxy groups. A radical mechanism was proposed based on cyclic voltammetry and control experiments.