in chloroform 48 h; Ambient temperaturein the dark;

1: 66 percent / p-toluenesulfonic acid / CHCl3 / 4 h / Heating 2: 99 percent / CHCl3 / 48 h / Ambient temperature; in the dark View Scheme

1: 66 percent / p-toluenesulfonic acid / CHCl3 / 4 h / Heating 2: 99 percent / CHCl3 / 48 h / Ambient temperature; in the dark View Scheme

1: 50 percent / Na2S2O4 / diethyl ether; H2O / 0.5 h / Ambient temperature 2: 66 percent / p-toluenesulfonic acid / CHCl3 / 4 h / Heating 3: 99 percent / CHCl3 / 48 h / Ambient temperature; in the dark View Scheme