Palladium-catalyzed cyclizative dimerization of alkynic hydrazones afforded 4,4'-bipyrazoles. The desired dimerization reaction proceeded efficiently by using the Pd(tfa)2/DPPF catalyst. Several functional groups were tolerated under the reaction conditions, and various bipyrazoles, including fully substituted bipyrazoles, were successfully synthesized.
Kusakabe et al. (2026) studied this question.