trifluoroacetic acid in dichloromethane 3 h; Ambient temperature;

1: 40 percent / DEAD; PPh3 / tetrahydrofuran 2: TFA View Scheme

1: 1.) 1,3-dicyclohexylcarbodiimide, CuCl / 1.) 60 deg C, 6 h, 2.) C6H6, reflux, 24 h 2: 45 percent / KF, Kryptofix 222 / dimethylsulfoxide / 24 h / 160 °C 3: 61 percent / aq. HBr / acetic acid / 3 h / Ambient temperature 4: 71 percent / triphenylphosphine, diethyl azodicarboxylate / tetrahydrofuran / 90 h / Ambient temperature 5: 74 percent / CF3COOH / CH2Cl2 / 3 h / Ambient temperature View Scheme

1: 61 percent / aq. HBr / acetic acid / 3 h / Ambient temperature 2: 71 percent / triphenylphosphine, diethyl azodicarboxylate / tetrahydrofuran / 90 h / Ambient temperature 3: 74 percent / CF3COOH / CH2Cl2 / 3 h / Ambient temperature View Scheme

1: 45 percent / KF, Kryptofix 222 / dimethylsulfoxide / 24 h / 160 °C 2: 61 percent / aq. HBr / acetic acid / 3 h / Ambient temperature 3: 71 percent / triphenylphosphine, diethyl azodicarboxylate / tetrahydrofuran / 90 h / Ambient temperature 4: 74 percent / CF3COOH / CH2Cl2 / 3 h / Ambient temperature View Scheme