Ciprofloxacin Hydrochloride‐Enhanced Potassium tert ‐Butoxide‐Mediated Direct Pyrazinylation of (Hetero)aryl Halides

Abstract

Aryl pyrazines are increasingly prevalent in the fields of pharmaceuticals and luminescent materials. Base‐promoted cross‐coupling reactions of (hetero)aryl halides with pyrazines can effectively avoid the drawbacks of limited substrate sources in conventional condensation and the cost as well as toxicity issues of noble metal catalysts inherent in transition metal‐catalyzed methods. However, existing methods are predominantly applicable to (hetero)aryl iodides and bromides, whereas the direct use of less reactive (hetero)aryl chlorides remains challenging. Herein, we report a ciprofloxacin hydrochloride with potassium tert ‐butoxide ( t ‐BuOK) catalytic system for the construction of aryl pyrazines. In this reaction, a variety of (hetero)aryl bromides and chlorides prove to be viable substrates and exhibit excellent compatibility with a variety of functional groups. The developed system allows the preparation of aryl pyrazines on a gram‐scale and the functionalization of complex pharmaceuticals. Mechanistic studies reveal that a radical‐mediated pathway is involved in this catalytic transformation.