1: 85 percent / PDC / dimethylformamide / 2 h / 0 °C 2: 1) n-BuLi / 1) THF, hexane, -78 deg C, 30 min, 2) THF, hexane, -78 deg C, 1 h then RT 3: MeOH, act. Dowex AG 50W acidic ion exch. resin / 3 h / 40 °C 4: Et3N / CH2Cl2 / 1 h / 0 °C 5: LiBr / tetrahydrofuran / 18 h / Heating View Scheme

1: 67 percent / MnO2 / CH2Cl2 / 24 h 2: 95 percent / n-BuLi / tetrahydrofuran; hexane / 1.) -78 deg C, 10 min; 2.) from -78 deg C to r.t. 3: 85 percent / CSA / methanol / 16 h / Ambient temperature 4: 64 percent / pyridine*SO3, Et3N / dimethylsulfoxide / 0.17 h View Scheme

dipyridinium dichromate in N,N-dimethyl-formamide T=0°C; 2 h;

1: 67 percent / MnO2 / CH2Cl2 / 24 h 2: 95 percent / n-BuLi / tetrahydrofuran; hexane / 1.) -78 deg C, 10 min; 2.) from -78 deg C to r.t. 3: 85 percent / CSA / methanol / 16 h / Ambient temperature View Scheme