hydroxybenzylic polymer; hydrogen bromide; acetic acid in diethylene glycol dimethyl ether T=150 - 160°C; multistep reaction; formation of p-benzyne; Mechanism;

Multi-step reaction with 2 steps 1: 2.) HBr / 1.) diglyme, reflux, 24 h; 2.) acetic acid, reflux, 48 h2: 1.) potassium persulphate / 1.) concd. H2SO4, -10 deg C, 15 min; 2.) -5 deg C, 1 h; 3.) 3 h, 0 deg C