1.1: DDQ / CH2Cl2; H2O / 6 h / 20 °C 2.1: Yb(OTf)3*H2O / CH2Cl2 / 7 h / 20 °C 3.1: 85 percent / triphenylphosphine; diisopropyl azodicarboxylate / tetrahydrofuran / 1 h / 65 °C 4.1: DDQ / CH2Cl2; H2O / 6 h / 20 °C 4.2: 30 percent / Yb(ONf)3*xH2O / CH2Cl2 / 24 h / 20 °C View Scheme

1: With 2,3-dicyano-5,6-dichloro-p-benzoquinone in dichloromethane; water T=20°C; 6 h; 2: With ytterbium(III) triflate in dichloromethane T=20°C; 3 h;

2,3-dicyano-5,6-dichloro-p-benzoquinone in dichloromethane; water T=20°C; 6 h;