1: 97.5 percent / p-toluenesulphonic acid / 20 h / 100 °C 2: 1.) O3, 2.) dimethylsulphide / MeOH, CH2Cl2; 1.) -78 deg C, 1.5 h, 2.) room t. 3: 99.6 percent / 70percent HClO4/Ac2O / ethyl acetate / 0.5 h / Ambient temperature 4: 86.2 percent / BCl3 / CH2Cl2 / 0.25 h / Ambient temperature View Scheme

PPA T=90 - 100°C; 2.5 h;

1: 84.6 percent / SnCl4 / CH2Cl2 / Ambient temperature 2: 86.9 percent / PPA / 2.5 h / 90 - 100 °C View Scheme

1: 84.6 percent / SnCl4 / CH2Cl2 / Ambient temperature 2: 86.9 percent / PPA / 2.5 h / 90 - 100 °C View Scheme