Rationalization of the mechanism and chemoselectivity of versatile Au-catalyzed reactions of diazoesters with allyl-functionalized sulfides, selenides, amines, or ethers by DFT

Abstract

The origin of chemoselectivity and the mechanism of the Au(I)-catalyzed [2,3]-sigmatropic rearrangement/cyclopropanation or C–H functionalization of diazoesters with allyl-functionalized sulfides, selenides, amines, or ethers as the second reactant were fully rationalized by density functional theory (DFT). The obtained results clearly indicate that the first step involves the formation of a gold carbene complex via the reaction of a Au(I) precursor with a diazoacetate substrate. In the major reaction pathway, the allyl-functionalized sulfides or selenides undergo a [2,3]-sigmatropic rearrangement via a free ylide intermediate. With an allyl amine as the second reactant, the main pathway is a selective para-C–H functionalization. However, an allyl ether as the second reactant mainly forms a cyclopropanation product through a concerted [2 + 1] cycloaddition reaction. Furthermore, the global reactivity index (GRI) analysis shows that the S or Se atoms of allyl sulfides or selenides possess a higher nucleophilicity index N_k compared to the O or N atoms of allyl ether or amine reactants, thus leading to distinct reaction pathways among the four model processes studied. In addition, the calculation results confirm that the [2,3]-sigmatropic rearrangement preferably occurs via a free ylide intermediate. This study provides novel synthetic possibilities and improves the reaction predictability when exploring the related types of Au-catalyzed organic transformations.