1: thionyl chloride / 3 h / Heating 2: 2.2 g / aluminium chloride / diethyl ether / 48 h / Heating 3: 1.) boron trichloride, 2.) 2M aq. sodium hydroxide / 1.) dichloromethane, 2.) methanol, pyridine, 18 h, reflux 4: 2.6 g / 45percent w/v HBr-glacial acetic acid / 4 h / Heating View Scheme

1: 1.) boron trichloride, 2.) 2M aq. sodium hydroxide / 1.) dichloromethane, 2.) methanol, pyridine, 18 h, reflux 2: 2.6 g / 45percent w/v HBr-glacial acetic acid / 4 h / Heating View Scheme

hydrogen bromide; acetic acid 4 h; Heating;