1.1: 80 percent / imidazole / dimethylformamide / 18 h / 20 °C 2.1: 70 percent / 1,2-dichloro-ethane / UV-irradiation 3.1: t-BuOK / tetrahydrofuran / 0.25 h / -105 °C 3.2: NCS / tetrahydrofuran / -105 - 25 °C 3.3: 60 percent / t-BuOK / tetrahydrofuran / 4 h / 20 °C 4.1: KNH(CH2)3NH2 / tetrahydrofuran / 15 h / 20 °C 4.2: 48 percent HF / acetonitrile / 20 °C 4.3: 45 percent / TFA; Et3SiH / benzene / 15 h / 20 °C 5.1: 80 percent / TFA; Pb(OTFA)4 / 0.5 h / 20 °C View Scheme