An efficient N-heterocyclic carbene-catalyzedoxidative esterification reaction of aldehydes with alkyl halides or alkyl 4-methylbenzenesulfonate is reported. It was worth noting that (1) the configuration of alkyl halides or alkyl 4-methylbenzenesulfonates was inverted completely, and (2) the presence of oxygen was crucial for this transformation. The reaction proceeded smoothly under mild conditions