12.1.5 Pyrazoles (Update 2017)

Abstract This review presents an overview of the developments in pyrazole synthesis since the beginning of the 21st century. It includes the synthesis of the pyrazole core by ring-closing reactions, ring expansion or contraction, and aromatization. The introduction of substituents onto the pyrazole ring is also covered. Novel synthetic methods that have been developed since the original Science of Synthesis review on pyrazoles (Section 12.1) include various multicomponent approaches in which multiple bonds are formed, cross coupling, and C—H activation reactions of pyrazole derivatives.