trifluoroacetic anhydride -15 deg C -> r.t., 2-3 d;

1: 1.) LDA / 1.) THF, -75 deg C, 0.5 h; 2.) HMPA, -70 deg C -> r.t. 2: 1.) mCPBA; 2.) trifluoroacetic anhydride / 1.) CH2Cl2, 0 deg C, 1 h; 2.) 0 deg C -> r.t., overnight 3: 80 percent / diethyl ether / 0.5 h / -20 - -17 °C 4: mCPBA / CH2Cl2 / -15 °C 5: (CF3CO)2O / -15 deg C -> r.t., 2-3 d View Scheme

1: 1.) mCPBA; 2.) trifluoroacetic anhydride / 1.) CH2Cl2, 0 deg C, 1 h; 2.) 0 deg C -> r.t., overnight 2: 80 percent / diethyl ether / 0.5 h / -20 - -17 °C 3: mCPBA / CH2Cl2 / -15 °C 4: (CF3CO)2O / -15 deg C -> r.t., 2-3 d View Scheme

1: 80 percent / diethyl ether / 0.5 h / -20 - -17 °C 2: mCPBA / CH2Cl2 / -15 °C 3: (CF3CO)2O / -15 deg C -> r.t., 2-3 d View Scheme

1: mCPBA / CH2Cl2 / -15 °C 2: (CF3CO)2O / -15 deg C -> r.t., 2-3 d View Scheme