Computational Exploration of the Nature of Li⁺-Ureide Anion Catalysis on Formation of Highly Reactive Vinyl Carbocations and Subsequent C–C Bond Forming Reactions

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The mechanisms of the C–H insertion reactions of vinyl carbocations formed by heterolysis of vinyl trifluoromethanesulfonates (triflates) by catalytic lithiated 1,3-bis[3,5-bis(trifluoromethyl)phenyl]urea (Li⁺-ureide) have been studied with ωB97X-D density functional theory. The ionization promoted by the Li⁺-ureide forms a metastable intimate ion pair complex of Li⁺-ureide-triflate anion and vinyl cation. The relative thermodynamic stabilities of isomeric alkyl cations are impacted by ion-pairing with the Li⁺-ureide-triflate anion. We show that the C–H insertion reaction of the vinyl cation intermediate is the rate-determining step and explain the effect of the aryl substituents on the formation of the vinyl cation and its C–H insertion reactivity as well as the regioselectivity of C–H activation by the vinyl cation.