toluene-4-sulfonic acid in N,N-dimethyl-formamide 4 h; Ambient temperature;

toluene-4-sulfonic acid in N,N-dimethyl-formamide 6 h;

1: 1. BF3*Et2O 2. trimethylsilyl trifluoromethanesulfonate / 1. CH2Cl2, room temperature 2. 1,2-dichloroethane 2: NaOCH3 / methanol 3: 3 g / p-TosOH / acetone / 1 h / Heating View Scheme

1: 4.6 g / pyridine 2: 1. BF3*Et2O 2. trimethylsilyl trifluoromethanesulfonate / 1. CH2Cl2, room temperature 2. 1,2-dichloroethane 3: NaOCH3 / methanol 4: 3 g / p-TosOH / acetone / 1 h / Heating View Scheme

1: NaOCH3 / methanol 2: 3 g / p-TosOH / acetone / 1 h / Heating View Scheme

1: 78 percent / barium oxide, barium hydroxide octahydrate / dimethylformamide / 16 h 2: 80.65 percent / trifluoroacetic acid / methanol; H2O View Scheme

1: 78 percent / barium oxide, barium hydroxide octahydrate / dimethylformamide / 16 h 2: 80.65 percent / trifluoroacetic acid / methanol; H2O 3: 1.) bis(tributylstannyl)oxide, 2.) tetrabutylammonium iodide / 1.) toluene, reflux, 16 h, 2.) reflux, 4 h View Scheme