N‐Heterocyclic Carbene Catalyzed Ester Synthesis from Organic Halides through Incorporation of Oxygen Atoms from Air

Abstract

Oxygenation reactions with molecular oxygen (O 2) as the oxygen source provides a green and straightforward strategy for the construction of O-containing compounds. Demonstrated here is a novel N-heterocyclic carbene (NHC) catalyzed oxidative transformation of simple and readily available organic halides into valuable esters through the incorporation of O-atoms from O 2. Mechanistic studies prove that the deoxy Breslow intermediate generated in situ is oxidized to a Breslow intermediate for further transformation by this oxidative protocol. This method broadens the field of NHC catalysis and promotes oxygenation reactions with O 2. Scheme 1. Dioxygen activation and esterification strategies.

Ni(II)-Mediated Photochemical Oxidative Esterification of Aldehydes with Phenols

“…In recent years, the direct oxidative esterification of aldehydes with alcohols to yield O-alkyl esters has attracted much attention, in part because aldehydes can be obtained from renewable resources. 7,8 This synthetic route proceeds through nucleophilic reaction of aldehyde with alcohol and then oxidation of the in situ formed hemiacetal. 9 Examples of the oxidative cross-coupling of aldehydes with phenols (Scheme 1d) are rather limited 10 because of the weak nucleophilicity and oxidative susceptibility of phenolates.…”