6-Chloro-4-ethynyl-1,4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one

6-Chloro-4-ethynyl-1,4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one is an intermediate in the synthesis of (4S)-6-Chloro-1-(1-((S)-6-chloro-2-oxo-4-(trifluoromethyl)-2,4-dihydro-1H-benzo[d][1,3]oxazin-4-yl)pent-1-yn-3-yl)-4-(pent-1-yn-1-yl)-4-(trifluoromethyl)-1H-benzo[d][1,3]oxazin-2(4H)-one (C360050), an impurity of Efavirenz (E425000) which is a nonnucleoside HIV-1 reverse transcriptase inhibitor. Antiviral.