Site-selective 2° C‒H chlorination of alkane by metal-free electrochemistry

The highly selective C(sp3)‒H bond activation strategy will greatly promote the efficient utilization of natural hydrocarbon resources. In the past few decades, chemists have developed effective methods to activate the 1° C‒H bonds with the smallest steric hindrance and the 3° C‒H bonds with the largest steric hindrance in alkanes. However, there is currently no effective strategy for activating the 2° C‒H bond with steric hindrance between the two. Here, we combine electrochemistry and organic catalysis to report a highly selective method for the chlorination of alkane 2° C‒H bonds. By adjusting the specific cavity size of the organic molecule catalyst to precisely undergo hydrogen atom transfer with the secondary C‒H bond, the corresponding carbon-centered free radicals are generated, which then combine with chlorine atoms to produce chlorinated alkanes at specific sites. In addition, the use of inexpensive and easily reusable graphite felt electrodes and simple electrochemical conditions makes it easy to scale up the system to kilogram-level production.