1: 1) 2N H2SO4, 2) hexamethyldisilazane / 1) acetone, 24h, 2) pyridine, 12h; 5h, 80 deg C 2: 97 percent / 2N H2SO4 / diethyl ether / 12 h 3: 20 percent / POCl3 / pyridine / 24 h / 70 °C 4: 58 percent / Zn / acetic acid / 72 h / 40 °C View Scheme