1: With 2,2,6,6-tetramethyl-piperidine; n-butyllithium in tetrahydrofuran; hexane T=-50°C; 1 h; 2: With boric acid trimethyl ester in tetrahydrofuran; hexane T=-75°C; 2 h; 3: With peracetic acid; acetic acid in tetrahydrofuran; hexane T=-75 - 20°C;

1.1: 85 percent / MeONa / dimethylformamide / 15 h / 0 - 20 °C 2.1: 2,2,6,6-tetramethylpiperidine; BuLi / tetrahydrofuran; hexane / 1 h / -50 °C 2.2: B(OMe)3 / tetrahydrofuran; hexane / 2 h / -75 °C 2.3: 63 percent / aq. AcOH; AcOOH / tetrahydrofuran; hexane / -75 - 20 °C View Scheme

1.1: 71 percent / Ag2CO3 / tetrahydrofuran / 15 h / 20 °C 2.1: BuLi / tetrahydrofuran; hexane / 0.25 h / -75 °C 2.2: ZnCl2 / tetrahydrofuran; hexane / -75 - 20 °C 2.3: 59 percent / [Pd(PPh3)4] / tetrahydrofuran; hexane / 20 h / Heating View Scheme

1.1: 69 percent / Ag2CO3 / tetrahydrofuran / 15 h / 20 °C 2.1: BuLi / tetrahydrofuran; hexane / 0.25 h / -75 °C 2.2: ZnCl2 / tetrahydrofuran; hexane / -75 - 20 °C 2.3: [Pd(PPh3)4] / tetrahydrofuran; hexane / 20 h / Heating 3.1: aq. HCl / tetrahydrofuran / 7 h / 50 °C 4.1: 71 percent / aq. HBr / acetic acid / 5 h / Heating View Scheme