1,8-diazabicyclo[5.4.0]undec-7-ene in tetrahydrofuran T=50°C; 3 h;

1: 1. NaH / 1. THF, a.) 0 deg C to r.t., b.) r.t., 0.5 h; 2. a.) 0 deg C to r.t., b.) r.t., 17 h 3: 1. trifluoroacetic anhydride (TFFA), DMSO; 2. Et3N / 1. CH2Cl2, -60 deg C, 2 h; 2. a.) -60 deg C, 1.5 h, b.) -60 deg C to 20 deg C, 0.5 h, c.) 2 h 4: 87 percent / pyridine / CH2Cl2 / 15 h / Ambient temperature 5: 94 percent / 1,8-diazabicyclo<5.4.0>undec-7-ene (DBU) / tetrahydrofuran / 3 h / 50 °C View Scheme

2: 1. trifluoroacetic anhydride (TFFA), DMSO; 2. Et3N / 1. CH2Cl2, -60 deg C, 2 h; 2. a.) -60 deg C, 1.5 h, b.) -60 deg C to 20 deg C, 0.5 h, c.) 2 h 3: 87 percent / pyridine / CH2Cl2 / 15 h / Ambient temperature 4: 94 percent / 1,8-diazabicyclo<5.4.0>undec-7-ene (DBU) / tetrahydrofuran / 3 h / 50 °C View Scheme

1: 87 percent / pyridine / CH2Cl2 / 15 h / Ambient temperature 2: 94 percent / 1,8-diazabicyclo<5.4.0>undec-7-ene (DBU) / tetrahydrofuran / 3 h / 50 °C View Scheme

1: 1. trifluoroacetic anhydride (TFFA), DMSO; 2. Et3N / 1. CH2Cl2, -60 deg C, 2 h; 2. a.) -60 deg C, 1.5 h, b.) -60 deg C to 20 deg C, 0.5 h, c.) 2 h 2: 87 percent / pyridine / CH2Cl2 / 15 h / Ambient temperature 3: 94 percent / 1,8-diazabicyclo<5.4.0>undec-7-ene (DBU) / tetrahydrofuran / 3 h / 50 °C View Scheme