1: 74 percent / NaHMDS; HMPA / tetrahydrofuran / 2 h / -78 - 0 °C 2: 83 percent / Ti(OiPr)4 / 70 °C 3: 97 percent / aq. HCl / tetrahydrofuran / 20 °C 4: Cs2CO3 / ethanol / 0 °C 5: Et3N / CH2Cl2 / 0 °C 6: 63 percent / LiHMDS / tetrahydrofuran / -78 - 0 °C View Scheme