Chiral Phosphine Ligand-controlled And Transition Metal-catalyzed Allylation And Silylation Reactions

Chiral phosphine ligands,the keys to asymmetric catalysis,play a vital role in asymmetric catalytic reactions.Thus,the design and development of reasonable new phosphine ligand is great significant.In 2013,we developed a new multidentate and multifunctional phosphine with multiple stereogenic centers,called Fei-Phos,for the catalytic asymmetricalkylation of allylic acetates with benzyl alcohols and silanols.And it was found that catalytic allylic alkylation of alcohols and silanols resulted in good to excellent yields and high enantioselectivities(up to 99%ee).In this paper,we will continue to study the application of Fei-Phos in asymmetric catalytic reaction,and study its structural characteristics and mechanism in asymmetric allylic reaction.On the other hand,we will continue to develop new ligands for silanization reaction.First,we have determined the beneficial features of Fei-Phos in palladium-catalyzed asymmetric allylic etherification of alcohols,silanols,asymmetric allylic alkylation of activated methylene compounds,indoles,and aromatic amines.All these catalytic transformations resulted in good to excellent yields and high enantioselectivities(up to 99%ee),which also showed this catalytic system,Pd/Fei-Phos complex,afforded the high level of enantioselectivity.All results indicated that Fei-Phos is an effective ligand in synthetically useful palladium-catalyzed asymmetric transformations.Secondly,on the basis of Pd/Fei-Phos complex as well as an equilibrium acidities(pK_a)of these nucleophiles,we have studied the role of Fei-Phos on the stereoselectivity and reactivity,which provided unexpected and interesting information for the mechanistic model of asymmetric palladium-catalyzed allylic alkylation in this work.A particularly appealing feature of the relationship of alcoholic substrate and reaction activity we outline here is that it is based on an equilibrium acidities(pK_a),which provided interesting and important information for the comparably mechanistic model of palladium-catalyzed asymmetric allylic alkylation of alcohols,activated methylene compounds,or indoles.The experimental results as well as the preliminary findings with relative energy analysis,ESI-MS,and NMR analysis,revealed that it is a diphosphine-controlled mechanistic pathway.Finally,we have developed successfully a new type of hydrosilylation of alkynes controlled by platinum catalyst with a monophosphine ligand,called as TBSO-MOP.The platinum-catalyzed multicomponent silylation of alkynes and alcohols with dihydrosilane,resulted in high stereoselectivity as well as high-yield construction of functional(E)-vinylsilyl ethers.Moreover,the one-pot bis-hydrosilylation of terminal alkynes with dihydrosilane was also achieved with the same platinum catalyst system.We have shown the powerful potential of phosphine ligand bearing silicon-based bulky group in chemoselectivity-controllable platinum-catalyzed multicomponent silylation.