E-Olefins Through NiH-Catalyzed Allyl Isomerization

Methylstyrene compounds are widely found in natural products and have important applications in the pharmaceutical,food,fragrance,materials and petrochemical arenas.In the past three decades,methylstyrene compounds through the isomerization of allyl groups catalyzed by transition metals such as palladium,ruthenium and ruthenium have been greatly developed.However,these catalysts are expensive and the reaction systems.are not mild enough.The E/Z ratios of products are aslo not ideal.By contrast,nickel is nonprecious,cheap and abundant.In recent years,our group has developed a S"nikel hydride"-catalyzed olefin isomerization and remote functionalization reaction system.The reaction has some advantages,mild conditions,highly isomerization of olefins.On this basis,this paper uses nickel as a catalyst to conduct a series of studies on how to achieve high-selective isomerization of ally]groups simply and efficiently.Most NiH-catalyzed systems require strong reducing agents such as silane or borane to provide a hydrogen source.However,these reducing agents are chemically unstable,which greatly limits the application of the catalytic system.Diethyl phosphite is a common chemical raw material with the advantages of chemical stability and low cost.In this paper,diethyl phosphite is used as hydrogen source and manganese powder is used as reducing agent.Allyl isomerization is achieved by catalytic system of NiI2 and 6,6'-dimethyl-2,2'-bipyridine.The reaction has lots of advantages,mild conditions,broad substrate scope good compatibility of functional groups.And the obtained methylstyrene products have highly E/Z selectivity.In the gram-scale experiment,we can further reduce the amount of the catalyst and the reaction can be carried out under solvent-free condition.Therefore,the reaction has high application value.