Recent Advances in Synergistic Catalysis by MergingN-Heterocyclic Carbenes and Transition Metals

Abstract

Unique reaction modes, diverse reaction sites, and structural diversity of both substrates and products have made N-heterocyclic carbene catalysis be of great of importance in the field of organic catalysis. However, there have been a lot of barriers and challenges in terms of the reactivity of substrates and the selectivity of reactions for traditional and single catalytic systems with the deep development of organic synthesis. Recently, synergistic catalysis makes it possible for previously inaccessible transformations and can adjust the reactivity and selectivity more accurately by merging two single catalytic systems, thus has emerged as a powerful catalytic strategy in organic synthesis. In this review, the latest research progress in the field of synergistic catalysis of N-heterocyclic carbenes and transition metals in the last decade is mainly reviewed.

Enantioselective SN2 Alkylation of Homoenolates by N‐Heterocyclic Carbene Catalysis

“…Typically, electrophilic β‐functionalization reactions employ a bifunctional reagent (E···Nu) to generate cyclic products, taking advantage of the intramolecular displacement of the NHC catalyst (by the nucleophilic warhead on the electrophile) for efficient catalyst turnover ( Figure 1 a ). [ 1 , 2 ] In comparison, non‐cyclizing β‐functionalization reactions have been restricted to a few electrophiles. Among these, β‐protonation reactions have been the most extensively studied, with Scheidt and our group independently devising practical protocols for enantioselective β‐protonation of enals.…”