Electrochemical Oxidative Clean Halogenation Using HX/NaX with Hydrogen Evolution

Abstract

Organic halides (R-X) are prevalent structural motifs in pharmaceutical molecules and key building blocks for the synthesis of fine chemicals. Although a number of routes are available in the literature for the synthesis of organic halides, these methods often require stoichiometric additives or oxidants, metal catalysts, leaving or directing groups, or toxic halogenating agents. In addition, the necessity of employing different, often tailor-made, catalytic systems for each type of substrate also limits the applicability of these methods. Herein, we report a clean halogenation by electrochemical oxidation with NaX/HX. A series of organic halides were prepared under metal catalyst- and exogenous-oxidant-free reaction conditions. It is worth noting that this reaction has a broad substrate scope; various heteroarenes, arenes, alkenes, alkynes, and even aliphatic hydrocarbons could be applied. Most importantly, the reaction could also be performed on a 200-mmol scale with the same efficiency (86%, 50.9 g pure product).