Use of Acylhydrazine- and Acylhydrazone-Type Ligands to Promote CuI-Catalyzed C-N Cross-Coupling Reactions of Aryl Bromides with N-Heterocycles

A series of ten acylhydrazine- and acylhydrazone-type ligands were designed and synthesized. Their electronic and steric properties were easily modified and tuned by varying the substituents in the vicinity of the acylhydrazine and acylhydrazone units. The effect of ligands on the catalytic activity of Ullmann reactions was assessed by using a combination of these ligands with CuI. The catalytic system is very efficient for the C-N coupling reaction of azoles with aryl and heteroaryl bromides.