triethyl amine hydrochloride in xylene 2 h; Heating / reflux;

in acetic acid 6.5 h; Heating;

1: 94 percent / p-toluenesulfonic acid / toluene / 4.5 h / Heating 2: 95 percent / tetrahydrofuran / 96 h / 23 °C 3: 85 percent / acetic acid / 6.5 h / Heating View Scheme

1: 95 percent / tetrahydrofuran / 96 h / 23 °C 2: 85 percent / acetic acid / 6.5 h / Heating View Scheme