Enantioselective N‐Heterocyclic Carbene Catalyzed α‐Oxidative Coupling of Enals with Carboxylic Acids Using an Iodine(III) Reagent.

The enantioselective α‐oxidative coupling of enals with carboxylic acids was developed via the umpolung of an NHC‐bound enolate with an iodine(III) reagent. The corresponding α‐acyloxyl‐β,γ‐unsaturated esters were afforded in good yields, with high regio‐ and enantioselectivities. The key step of the reaction involves the formation of enol iodine(III) intermediate from the enolate with iodosobenzene, which changes the polarity of α‐carbon of the enal from nucleophilic to electrophilic, and thus facilitates the subsequent addition of carboxylate. [ABSTRACT FROM AUTHOR]