1: With pyridinium p-toluenesulfonate; trimethyl orthoformate in dichloromethane T=20°C; 2 h; 2: With acetyl-bromide in dichloromethane T=20°C; 4 h; 3: With tetrabutylammomium bromide; potassium hydrogencarbonate in ethylene glycol dimethyl ether T=40°C; 27 h;