| Olefin metathesis, the essence of which is the broken and re-assembly process of the double bonds, is widely used in organic synthesis, especially in the fields of polymer materials, natural products and synthetic drugs. Olefin metathesis catalytic systems mainly have Shrock’s W, Mo catalysts and Grubb’s Ru catalysts. Ru catalysts, due to their good stability and ease of synthesis, etc. has been widely developed. However, ruthenium catalyst still suffers from the problems of high cost and metal contamination in products. Though a variety of supported ruthenium catalysts had been developed to soleve these isues, the catalyst’s recycle times is low and inconvenient separation difficulties still exist. Therefore, the development of a more efficient and easy to separated catalyst is still a challenge task. To solve the above problems, we designed an ion chain modified ruthenium carbene catalyst and supported it on magnetic iron oxide particles. The newly developed catalyst is highly efficient and can be reused 14 times. Moroever, the catalyst enable easy magnetic separation.This paper focuses on demonstrating the following innovative achievements:(1) According to the relevant literature, the ionic liquid catalyst as part of the modification of catalyst can increase catalytic activity, stability and repeated use of the reaction. So we synthesized the ionic liquids modified ruthenium carbene catalyst.(2) The above catalyst was supported to the surface of iron oxide particles to prepare the catalyst A. Catalyst A was used to ring close metathesis reaction. The catalyst can be used up to 7 times, and the conversion for the last time is > 75%. The catalyst A-catalyzed RCM reaction went smoothly even for larger steric substrate and provided tetra-substituted alkene with a conversion > 90%.(3) The ionic liquids modified ruthenium carbene catalyst was also supported to the surface of silica-coated Fe3O4 particals. The obtained catalyst B is more reactive than catalyst A, and used up to 14 times(> 90% conversion).(4) Both catalyst A and B are highly efficient for cross-metathesis reaction. They were used in the cross-metathesis reaction between 4-pentenoic acid alcohol ester and methyl acrylate, and between allylbenzene and methyl acrylate. The conversion rates for 4-pentenoic acid alcohol ester and allylbenzene are> 95%. |
