The effect of substituents on carbon–carbon double bond isomerization in heterocyclic hydrazine derivatives

Even though enehydrazide moiety is present in many pharmaceuticals, there is currently no straightforward method available for preparing cyclic enehydrazides, which could be valuable building blocks in anticancer research. Herein, we report how electronic effects and ring size influence the direction and yield of Ru catalytic carbon–carbon double bond isomerization in heterocyclic enehydrazines. Having the knowledge of how variation of these properties affects the equilibrium between double bond isomers enables us to control the outcome when preparing different cyclic enehydrazides. Six enehydrazide heterocycles and five enehydrazine heterocycles were synthesized and characterized with the current method. In addition, cytotoxicity evaluation of the synthesized compounds showed that several heterocycles produced in this study could be used in developing anticancer drugs.