4 A molecular sieve; toluene-4-sulfonic acid in toluene Heating;

1: 90 percent / triethylamine / 4-(dimethylamino)pyridine / tetrahydrofuran / Heating 2: 66 percent / p-toluenesulfonic acid monohydrate, 4 Angstroem molecular sieves / toluene / Heating View Scheme

trifluoroacetic acid 2.5 h; Ambient temperature;

1: 54 percent / LDA / tetrahydrofuran / 1.33 h / -78 °C 2: 72 percent / TFA / 2.5 h / Ambient temperature View Scheme