Computational Insights into the Gold‐Catalyzed Ring‐Opening of Methylenecyclopropanes and Vinylcyclopropanes with Sulfonamides

Abstract Computational studies were carried out to investigate the mechanisms of gold‐catalyzed ring‐opening of methylenecyclopropanes (MCPs) and vinylcyclopropanes (VCPs), respectively, with sulfonamides to afford homoallylic amine intermediates, which would subsequently produce pyrrolidine derivatives. The detailed activation modes of MCPs mediated by the Au I catalyst were comprehensively explored. Computational results suggested that the activation of MCP by the Au I catalyst was less feasible. Instead, the Au I catalyst mediated activation of sulfonamides could result in the increased acidity of the N−H bond, which is ready to undergo intermolecular proton transfer to the C=C moiety of MCP to form a cyclopropylcarbinyl cation intermediate. Subsequently, the nucleophilic attack of the formed amido group to the three‐membered ring moiety of the yielded cyclopropylcarbinyl cation intermediate in an S N 2 manner could follow to afford the ring‐opening homoallylic sulfonamide. In addition, computational studies indicated that such mechanistic pathway could also apply to the VCPs involved hydroamination with sulfonamides. The mechanism of triflic acid catalyzed hydroamination of MCPs and VCPs with sulfonamides also proceeds via the cyclopropylcarbinyl cation intermediates formed by the protonation of the alkene moiety of MCPs and VCPs, respectively. The ineffectiveness of amines as aminating reagents in the Au I ‐catalyzed hydroamination of MCPs and VCPs was discussed.