摘要
Catalytic asymmetric transformations of ynamides have attracted considerable attention in recent years.However,most of them were limited to intramolecular reactions or required metal catalysts.Herein,a chiral Br?nsted acid-catalyzed asymmetric intermolecular[4+2]annulation of ynamides with para-quinone methides(p-QMs)is disclosed,which not only represents the first metal-free protocol for catalytic asymmetric nucleophilic addition of ynamides to electrophiles,but also constitutes the first enantioselective annulation between p-QMs and alkynes.This methodology leads to the practical synthesis of biologically important chiral 4-aryl-3,4-dihydrocoumarins and 4-aryl-coumarins.Preliminary control experiments indicate that the orthohydroxyphenyl substituted p-QMs could isomerize into ortho-quinone methides(o-QMs)in the presence of chiral catalyst,which further react with ynamides via enantioselective[4+2]annulation,to generate the chiral product.
基金
supported by the Ministry of Science and Technology(MOST)(2021YFC2100100)
the National Natural Science Foundation of China(22125108,22121001,92056104)
the President Research Funds from Xiamen University(20720210002)
the Natural Science Foundation of Jiangsu Province(BK20211059)
the Project of Science and Technology of Xuzhou Government(KC22080)
the National Fund for Fostering Talents of Basic Science(NFFTBS)(J1310024)。
