107.5 g of 3,5-di-tert-butyl-4-hydroxybenzoyl chloride and 48.4 g of resorcinol are suspended in 400 ml of nitrobenzene and warmed to 50° C. The brown solution is cooled to 0° C. 58.7 g of aluminium chloride are added in portions over the course of 45 minutes with vigorous stirring. The reaction mixture is slowly warmed to 20° C. over the course of 18 hours. The mixture is subsequently stirred at 50° C. for a further 4 hours, then cooled to room temperature and poured into 500 ml of hydrochloric acid/ice. The thick yellow suspension is extracted with ether, the ether phase is extracted with 500 ml of sodium hydroxide (15%), and the basic solution is washed three times with 250 ml of ether in each case, acidified to a pH of 1-2 using 15% hydrochloric acid and extracted with ether. The ether extracts are combined, dried and evaporated under reduced pressure, giving 124.4 g of 3,5-di-tert-butyl-2',4,4'-trihydroxybenzophenone, which, after recrystallisation from methanol, has a melting point of 192°-193° C.
