thionyl chloride 1 h; Heating;

hydrogen bromide 8 h; Heating;

phosphorus tribromide

1: With oxalyl dichloride; dimethyl sulfoxide in dichloromethane T=-60°C; Swern Oxidation; 0.25 h; Inert atmosphere; 2: With triethylamine in dichloromethane T=20°C; Swern Oxidation; 5 h; CoolingInert atmosphere;