potassium hydrogensulfate T=80°C; P=10 Torr; 0.5 h;

With  potassium hydrogensulfate T=70°C;  under vacuum;   

Multi-step reaction with 3 steps 1: 88 percent / trimethyl phosphite / CHCl3 / 48 h / Heating2: 75 percent / benzene / 18 h / Irradiation3: 78 percent / diethyl ether / 1.5 h  

Multi-step reaction with 2 steps 1: 75 percent / benzene / 18 h / Irradiation2: 78 percent / diethyl ether / 1.5 h