Palladium Complexes with N,O‐Bidentate Ligands Based on N‐Oxide Units from Cyclic Secondary Amines: Synthesis and Catalytic Application in Mizoroki‐Heck Reaction

Abstract

Comprehensive SummaryPalladium‐catalyzed Mizoroki‐Heck reaction is a powerful and efficient method for construction of Csp2–Csp2 bonds. Herein, four palladium complexes (I—IV) with N,O‐bidentate ligands (L1—L4) based on N‐oxide units from cyclic secondary amines were easily synthesized and successfully applied in Mizoroki‐Heck reaction of aryl bromides with electron‐deficient olefins. X‐ray diffraction analyses indicated the palladium(II) atom of II took the distorted square planar geometry and was four‐coordinated by nitrogen and oxygen atoms from two ligands (L2). Two free chloride ions were presented as counter anions in complex II. But the palladium(II) center of IV was coordinated by nitrogen and oxygen atoms from one ligand (L4) as well as two chlorine atoms, which exhibited the nearly square‐planar geometry. The study on catalytic properties of palladium complexes revealed that complex II exhibited high activity superior to the other complexes. The coupling reactions of a series of aryl bromides and olefin derivatives proceeded in the presence of 2—5 mol% palladium complex II, giving the desired products in good to excellent yields. The advantages of this method such as good compatibility of functional groups, high yields, and short reaction times made it more attractive for constructing Csp2–Csp2 bonds in the synthesis of functional molecules and materials.