1: caesium carbonate; tris-(dibenzylideneacetone)dipalladium(0); 9,9-dimethyl-4,5-bis(diphenyl-phosphino)xanthene / toluene; 1,4-dioxane / 8 h / 99 °C / |Inert atmosphere 2: anhydrous potassium trimethylsilanolate / N,N-dimethyl-formamide; tetrahydrofuran / 1.67 h / 20 - 25 °C / |Inert atmosphere 3: 1,1'-carbonyldiimidazole / tetrahydrofuran / 2 h / 20 - 50 °C 4: N,N-dimethyl-formamide; tetrahydrofuran / 1 h / 50 °C / |Inert atmosphere 5: phosphoric acid; water / acetonitrile / 6.25 h / 20 - 53 °C View Scheme

1: caesium carbonate; tris-(dibenzylideneacetone)dipalladium(0); 9,9-dimethyl-4,5-bis(diphenyl-phosphino)xanthene / toluene; 1,4-dioxane / 8 h / 99 °C / |Inert atmosphere 2: anhydrous potassium trimethylsilanolate / N,N-dimethyl-formamide; tetrahydrofuran / 1.67 h / 20 - 25 °C / |Inert atmosphere 3: 1,1'-carbonyldiimidazole / tetrahydrofuran / 2 h / 20 - 50 °C 4: N,N-dimethyl-formamide; tetrahydrofuran / 1 h / 50 °C / |Inert atmosphere 5: phosphoric acid; water / acetonitrile / 6.25 h / 20 - 53 °C View Scheme

1: potassium carbonate / N,N-dimethyl-formamide / 1 h / 75 °C 2: water; sodium hydroxide / tetrahydrofuran / 2 h 3: benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride / N,N-dimethyl-formamide / 48 h / 20 °C 4: hydrogenchloride / ethanol / 24 h View Scheme