Transition-metal-catalyzed C-H functionalization of pyrazoles

This review describes recent advances in transition-metal-catalyzed C-H functionalization reactions of pyrazoles to form new C-C and C-heteroatom bonds on the pyrazole ring. In contrast to traditional cross-coupling reactions that require pre-functionalized pyrazoles, direct C-H functionalization reactions provide access to a wide range of functionalized pyrazoles in a single step. Various strategies are presented and the efficiency and regioselectivity are described with respect to the types of functional groups that are installed.