摘要
Density functional calculations have been performed to comparatively investigate two possible pathways of Au（I）-catalyzed Conia-ene reaction of β-ketoesters with alkynes. Our studies find that, under the assistance of trifluoromethanesulfonate （TfO）, the β-ketoester is the most likely to undergo Model II to isomerize into its enol form, in which TfO plays a proton transfer role through a 6-membered ring transition state. The coordination of the Au（I） catalyst to the alkynes triple bond can enhance the eletrophilic capability and reaction activity of the alkynes moiety, which triggers the nucleophilic addition of the enol moiety on the alkynes moiety to give a vinyl-Au intermediate. This cycloisomerizaion step is exothermal by 21.3 kJ/mol with an energy barrier of 56.0 kJ/mol. In the whole catalytic process, the protonation of vinyl-Au is almost spontaneous, and the formation of enol is a rate-limiting step. The generation of enol and the activation of Au（I） catalyst on the alkynes are the key reasons why the Conia-ene reaction can occur in mild condition. These calculations support that Au（I）-catalyzed Conia-ene reactions of β-ketoesters with alkynes go through the pathway 2 proposed by Toste.
Density functional calculations have been performed to comparatively investigate two possible pathways of Au（I）-catalyzed Conia-ene reaction of β-ketoesters with alkynes. Our studies find that, under the assistance of trifluoromethanesulfonate （TfO）, the β-ketoester is the most likely to undergo Model II to isomerize into its enol form, in which TfO plays a proton transfer role through a 6-membered ring transition state. The coordination of the Au（I） catalyst to the alkynes triple bond can enhance the eletrophilic capability and reaction activity of the alkynes moiety, which triggers the nucleophilic addition of the enol moiety on the alkynes moiety to give a vinyl-Au intermediate. This cycloisomerizaion step is exothermal by 21.3 kJ/mol with an energy barrier of 56.0 kJ/mol. In the whole catalytic process, the protonation of vinyl-Au is almost spontaneous, and the formation of enol is a rate-limiting step. The generation of enol and the activation of Au（I） catalyst on the alkynes are the key reasons why the Conia-ene reaction can occur in mild condition. These calculations support that Au（I）-catalyzed Conia-ene reactions of β-ketoesters with alkynes go through the pathway 2 proposed by Toste.
