A mild halogenation of pyrazoles using sodium halide salts and Oxone

Kathryn L. Olsen, Elizabethtown College
Matthew R. Jensen, Elizabethtown College
James A. MacKay, Elizabethtown College


A mild, inexpensive, and operationally simple pyrazole halogenation method utilizing Oxone and sodium halide salts is reported. This work documents 17 examples of alkyl, aryl, allyl, and benzyl substituted 4-chloro and 4-bromopyrazoles, obtained in up to 93% yield. Reactions are performed in water under ambient conditions and generation of organic byproducts is avoided.