dipyridinium dichromate in N,N-dimethyl-formamide T=20°C; 24 h;

1: 45 percent / p-TsOH / methanol / 3 h / 45 °C 2: 49 percent / pyridinium dichromate / dimethylformamide / 24 h / 20 °C View Scheme

1.1: n-BuLi / tetrahydrofuran; hexane / 1.33 h / 20 °C 1.2: 82 percent / tetrahydrofuran; hexane; hexamethylphosphoric acid triamide / 24 h / -60 °C 2.1: 45 percent / p-TsOH / methanol / 3 h / 45 °C 3.1: 49 percent / pyridinium dichromate / dimethylformamide / 24 h / 20 °C View Scheme

1.1: n-BuLi / tetrahydrofuran; hexane / 1.33 h / 20 °C 1.2: 82 percent / tetrahydrofuran; hexane; hexamethylphosphoric acid triamide / 24 h / -60 °C 2.1: 45 percent / p-TsOH / methanol / 3 h / 45 °C 3.1: 49 percent / pyridinium dichromate / dimethylformamide / 24 h / 20 °C View Scheme