Studies On The Palladium-catalyzed Asymmetric Addition Of Arylboronic Acids To Nitrostyrenes And Exo-cyclic Ketimines

Transition-metal-catalyzed asymmetric additions of organometallic reagents to electron-deficient double bonds represent useful strategies to construct C-C bonds with formation of chiral centers,which is widely applied in total synthesis of complex chiral molecules.The addition of hard organometallic reagents to electron-deficient double bonds has been well-studied.For addition using soft organometallic nucleophiles especially arylboron reagents,rhodium complexes using chiral diphoshpine,diene,sulfur-olefin,and so on,as ligands,performed as efficient catalysts showing high enantioselectivity and activity,which became a topic of longstanding interest.Alternatively,using palladium catalysts in the same reaction is an attractive methodology due to their lower cost compared to rhodium catalysts.Therefore,considerable efforts have been directed toward the developing of palladium-catalyzed asymmetric additions of arylboron reagent.The first part of this thesis describes palladium-catalyzed asymmetric addition of arylboronic acids to nitrostyrenes,developed a very simple and high effcient[Pd?TFA?₂/IsoQuinox/MeOH]catalytic system.After screening chiral ligands,solvents,temperature and other conditions,we found that when using the Pd?TFA?₂ catalyst,IsoQuinox chiral ligands,methanol solvent at 40 ^oC conditions obtain maximum yield of 92%and 96%of ee.We report the first palladium catalyzed asymmetric addition of arylboronic acids to nitrostyrenes.The catalysis could provide the desired chiral nitro products with good enantioseletivities and yields.A range of nitrostyrenes and arylboronic acids are tolerable to the reaction conditions.The second part of this thesis demonstrates Pd?II?-catalyzed asymmetric addition of arylboronic acids to isatin-derived ketimines,a very simple[Pd?TFA?₂/Pyrox/TFE]catalytic system have been developed,providing chiral 3-amino-2-oxindoles with a quaternary stereocenter in high yields and with good enantioselectivities.Additionally,the majority of the reactions could be performed in open air and with unpurified solvents.A variety of functionalized 3-ketimino oxindoles can be used,and this method tolerates some variation in arylboronic acid scope.This asymmetric arylation provide an alternative efficient catalytic method for preparation of chiral 3-aryl-3-amino-2-oxindoles,which is also the first example of Pd?II?-catalyzed addition of arylboron to exo-cyclic ketimines.