6-Chloro-4-(2,2,2-trifluoroacetyl)benzo[d]oxazol-2(3H)-one is an intermediate in the synthesis of 6-Chloro-4-[3-cyclopropyl-1-hydroxy-1-(trifluoromethyl)-2-propyn-1-yl]-2(3H)-benzoxazolone (C365790), a impurity of Efavirenz (E425000) which is a nonnucleoside HIV-1 reverse transcriptase inhibitor.