potassium hydroxide in ethanol; water

sulfuric acid in tetrahydrofuran 72 h; Ambient temperature;

1: hex-5-ynoic acid With n-butyllithium in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide T=-40°C; Metallation; 1 h; 2: formaldehyd in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide T=20°C; Addition; 2 h;

1: 92 percent / dimethylsulfoxide / 20 h / 80 °C 2: 85 percent / 10percent aq. NaOH / methanol / Heating 3: 70 percent / p-toluenesulfonic acid / H2O; tetrahydrofuran View Scheme

1: 85 percent / dimethylformamide / 3 h / 120 °C 2: 92 percent / K2CO3 / methanol / 18 h 3: 82 percent / pyridinium dichromate / dimethylformamide 4: 70 percent / p-toluenesulfonic acid / H2O; tetrahydrofuran View Scheme

1: 82 percent / pyridinium dichromate / dimethylformamide 2: 70 percent / p-toluenesulfonic acid / H2O; tetrahydrofuran View Scheme