Synthesis of Chlorfenazole from 2-Chlorobenzalmalononitrile Extracted from Expired Tear-Gas Grenade

Tear gases were originally manufactured as weapons that could severely disable or kill enemy troops. Though banned in war, these chemicals are still used in domestic policing. Due to ammunition management rules, a large number of tear-gas grenades are scrapped every year and need to be safely destroyed. 2-chlorobenzalmalononitrile (CS) is commonly used as the tear-inducing agent in tear-gas grenade. Herein, we report a novel method to valorize waste CS. It includes (i) extraction of CS from expired tear gas grenade, and (ii) a Lewis acid-catalyzed reaction of CS and o-phenylenediamine to synthesize chlorfenazole, a commercialized benzimidazole-based drug used to treat intestinal nematodoses.