Synthesis Of N-heterocyclic Carbene (NHC)-metal Complexes Derived From Proline And Their Applications

The thesis mainly focused on the synthesis of N-heterocyclic carbene (NHC)-palladium and rhodium complexes derived from L-proline and their catalytic activity in carbon-carbon bond formations. In addition, novel well-defined NHC-Pd-Im complexes were synthesized and their catalytic activities in Suzuki-Miyaura coupling of aryl chlorides were investigated. The thesis can be divided into the following parts:1. NHC-Pd(II) complexes derived from proline have been successfully synthesized in good yields and their structures have been characterized by X-ray single crystal diffraction. It was found that the substituents on the N-atom of the pyrrolidine skeleton dramatically affect on the coordination pattern of the palladium complexes. In a word, when an electron-rich group such as benzyl group was attached on the//-atom, both of the N-atom and NHC were coordinated to the Pd(II) center; while when an electron-poor group such as Ts group was attached, a dimeric mono-coordinated Pd(II)-NHC was obtained exclusively.2. Applications of NHC-Pd(II) complexes derived from proline in carbon-carbon bond formations were carried out and it was found that the complexes are highly effective catalyst in Suzuki-Miyaura and Mizoroki-Heck reactions of aryl iodides and bromides performed in neat water.3. Novel NHC-Rh(I) complexes derived from N-benzyl substituted proline have been successfully synthesized and were found to be efficient catalysts for the 1,4-conjugate addition of arylboronic acids to enones in neat water at 40℃. Under the optimal reaction conditions, all reactions gave the addition products in good to high yields.4. A new type of well-defined NHC-palladium chloride-imidazole complexes was synthesized from readily available starting materials as IPrHCl or IMes'HCl with PdCl2 and 1-methylimidazole. These air-and moisture stable NHC-Pd(II)-Im complexes exhibit high catalytic activity in the Suzuki-Miyaura coupling reactions of aryl or heteroaryl chlorides. Moreover, the large-scale (20.0 mmol) couplings in the presence of 0.01 mol% catalyst loading can also give the corresponding coupling products in high yields. These contents are displayed in the Appendix.