Studies On The Copper Catalyzed Dipolar Cycloaddition Of Alkynes

1,3-Dipolar cycloaddition is one of the most important reactions in organic chemistry. It has provided to be a powerful tool for the synthesis of five-membered heterocycles. In past years, copper(I) catalyzed 1,3-dipolar cycloaddition has been became a remarkable"click reaction"with mild conditions and high regioselectivity. In this dissertation, copper catalyzed cycloaddtion between azide and azomethine imine with alkyne were studied and several catalyst systems were developed.Four catalytic systems for cycloaddition of azide and alkyne (CuAAC) were developed: CuOAc,Cu2O-HOAc,CuI and TBAA. The reaction was accelerated remarkablely by catalytic amount of carboxylic acid. Acetate acid may play three important roles: (1) formation of dinuclear coordination with Cu(I); (2) formation of active catalytic species with phenylethynylcopper(I); (3) protonation of the intermediate 5-copper substituted 1,2,3-triazoles. These systems were highly efficient in low loading without any ligands or additives.The CuAAC reaction catalyzed by Cu(OAc)₂ was developed and its catalytic effect was regulated by ligands. The real catalyst is CuOAc, which was produced in situ by reduction of Cu(OAc)₂. The process was influenced greatly by the structure of ligand and the ratio of copper. Many carboxylic coppers exhibited good activity and Cu(OAc)₂ was the most convenient choice, which proved to be a very stable, inexpensive and highly efficent catalyst in CuAAC reactions.The cycloaddtions of azomethine imines with alkynes could be catalyzed by the above catalytic systems under very mild condtions. Additionally, TBAF could also promote the reaction efficiently combined with CuI. Copper acetylides was prepared from propiolates by the above systems and proved to be the intermediate of the reaction. Comparing with reference results, these catalytic systems were very simple and efficient.Additionally, a procedure for Kumada reaction promoted by nickel with oxime ligand was developed and a series of biaryl products were prepared.