Mechanism of the oxidative nonpolar inversion reaction catalyzed by N-heterocyclic carbenes (NHCs) to achieve benzoxazoles was investigated in very details. The reaction was revealed to occur through five processes, and for oxidation in the second process, two successive tautomerizations followed by oxidation were demonstrated to be more energetically favorable than the other two pathways. The rate-determining step was disclosed to be the oxidation by 3,3’-5,5’-tetra-tert-butyl-4,4’-diphenoquinone (DQ). Afterwards, mechanism calculations to the non-catalyzed reaction was conducted and it was revealed that the excessive exothermic property of the initial step should be the main reason for the extremely high barrier in the following step. While with participation of NHC, this unfavorable transformation can be deftly prevented according to the specific sequence and amount of reagents addition, and therefore to enable the reaction to occur under mild conditions.