Oxidative functionalization of yndiamides catalyzed by gold(i) or Brønsted acid systems: computational study of mechanism, selectivity patterns, and effects of substituents

Abstract

The mechanism, regioselectivity, chemoselectivity, and the effects of substituents were explored using density functional theory (DFT) in the oxidative functionalization of yndiamides catalysed by gold(I) [IPrAuNTf₂] or Brønsted acid (HNTf₂) systems. The calculations revealed that both catalysts entail a similar type of nucleophilic attack on the catalyst-ligated yndiamide, forming a vinyl intermediate that can isomerize to gold carbene or carbocation upon the cleavage of the N–O bond. Next, the gold carbene or carbocation is easily captured by external nucleophilic reagents and finally desaturated via a proton shift, assisted by a substrate or NTf₂⁻ to yield the final product. The unique features of regio- and chemoselectivity were explored in detail through distortion/interaction and global reactivity index (GRI) analyses. The effects of substituents in yndiamides were also investigated. Apart from completely rationalizing the experimental data and intricate selectivity patterns, the obtained theoretical evidence can provide a significant contribution toward understanding the resembling types of reaction mechanisms.