1.1: 54 g / DIPEA / CH2Cl2 / 2 h / -40 °C 2.1: LHMDS / tetrahydrofuran; hexamethylphosphoric acid triamide / 3 h / -78 °C 2.2: 63.3 percent / 2 h 3.1: 4.5 g / DIPEA; DMAP / CH2Cl2 / -23 - 20 °C 4.1: 1.53 g / DBU / toluene / 0 - 50 °C 5.1: 30 percent / DDQ / CH2Cl2; H2O / 20 °C 6.1: 2 mg / TFA / CH2Cl2 / 0 - 20 °C View Scheme