Based on the Wangs experiment,1 the reaction mechanism,stereoselectivity,and chemoselectivity on oxidative α-fluorination of aliphatic aldehydes via α C(sp3)-H activation enabled by N-heterocyclic carbene catalysis,have been investigated in detail using the density functional theory(DFT)method,which has been widely used to explore the organocatalytic reactions.2-6 According to the computational results,the fluorination process is identified to be the stereoselectivity-determining step and the addition on the prochiral face of enolate intermediate results in the formation of stereoselective fluorinated intermediate.