Study On The Addition Of Alkynes Catalyzed By Asymmetric Diacids

Through the synergistic catalysis strategy of Lewis acid and chiral phosphoric acid,the asymmetric catalytic reaction that is difficult to be realized by a single catalyst can be efficiently and powerfully achieved,which greatly breaks through the limitation of a single catalyst.In the previous work,our research group realized a series of reactions for the asymmetric addition of?,?-unsaturated?-ketoesters under the binary catalysis strategy.In(III)/CPA synergistic catalysis could realize the asymmetric addition reaction of alkynes to?,?-unsaturated?-ketoesters.In addition,we also verified the possibility of asymmetric[4+2]cycloaddition of alkynes by Hf Cl₄/CPA.This paper mainly discusses the addition reaction of alkynes and?,?-unsaturated?-ketoesters.The main contents include:(1)Hf(?)-catalyzed[4+2]cycloaddition of alkynes and?,?-unsaturated?-ketoesters.The cycloaddition reaction of various symmetrical and asymmetric internal alkynes is catalyzed by Hf Cl₄,giving the cycloadducts in up 98%yield and with excellent regioselectivity(up to>99:1).In addition,the possibility of asymmetric[4+2]cycloaddition was verified by the Hf(IV)/CPA combination strategy.(2)The asymmetric addition reaction of alkynes was successfully realized by asymmetric binary-acid catallyst In(III)/CPA.In this catalytic strategy,the adduct was afforded in up to 92%yield and with up to 98%ee.During this process we also observed unprecedented synergistic combinations controlled switch of enantio-selectivity.In addition to different 3,3'-substitutents of one single chiral phosphoric acid,the use of both catalytic amount of silver salt and chemical amount of protic solvent(e.g.,ethanol)is crucial for switchable enantioselectivity.