Investigation Of Silylcobalt Tetracarbonyls-Catalyzed Alternating Copolymerization Of Imine With Co And Three-component Cycloaddition Of Epoxides,Imines And Co

Polypeptides are important biopolymers that have been used for a broad range of applications in material, catalysis and pharmaceuticals. Polypeptide synthesis has attracted widespread interest of research in the past years. There have been some very useful methods for preparation of polypeptides, but most of them are based on the use of amino acids as starting materials, which require tedious procedures and produce large amount of by products. In recent years, inspired by the development of transition metal catalyzed polymerization reactions, researchers have begun to attempt the possibility of metal catalyzed copolymerization of imines with CO for synthesis of polypeptides. In this field, our group has reported for the first time the realization of alternating copolymerization of imines and CO catalyzed by phenylacetyl cobalt tetracarbonyls.Based on the successful study, silylcobalt tetracarbonyls compounds, which are specially stable and more convenient to be accurately utilized and operated, were synthesized and used as catalysts for alternating copolymerization of imines and CO. Under the optimized conditions, the catalysts were tested and successfully provided the alternating copolymers. In situ IR techniques were employed to explore the mechanism of the silylcobalt tetracarbonyls-catalyzed alternating copolymerization of imines and CO. Meanwhile, kinetic investigation of the reaction was undertaken in order to gain more insight into the mechanism of the ring-opening process. Two kinds of stable mono-phosphine-substituted acylcobalt compounds were obtained, and their structures were determined by X-ray diffraction methods, further verifying the ring-opening reaction leading to acylcobalt tetracarbonyls complexes as the real active catalysts. Moreover, a new method for operation of the copolymerization, named the modified copolymerization, has been developed, which is applicable for a variety of imine monomers. Especially for aromatic aldehyde imine,100%conversion to the copolymerization products was achieved. When aliphatic aldehyde imines were used, the quantitative conversion can be maintained even at high molecular ratios, affording high molecular weight polypeptides with low polydispersity. Three kinds of new stable acylcobalt tetracarbonyl complexes were successfully isolated, and single crystal X-ray diffraction analyses of the compounds were completed demonstrating the acylcobalt tetracarbonyl structures. Catalytic performances of these catalysts were evaluated and all displayed the characteristics of living polymerization behavior. Thus, polypeptides containing hydroxyl and other functionalized end group and block polymers from different monomers were obtained, which laid further foundation for functionalization and application of the polypeptides.A new HCo(CO)4catalyzed three-component cycloaddition of epoxides, imines and CO was developed. This reaction takes places for a wide variety of imines and epoxides, to provide1,3-oxazinan-4-ones with different substituted patterns. Twenty-six of the heterocyclic compounds were firstly prepared, and the herbicidal activities of these products were tested. Moreover, the reaction kinetics was investigated by in situ IR method, and a possible catalytic cycle for this novel cycloaddition has been proposed.