A solution of 3-bromo-5-(tert-butyl)-2-hydroxybenzaldehyde (Intermediate 4) (4 g, 15.56 mmol) in DME (30 mL) and water (10 mL) was purged with nitrogen for 15 minutes. Potassium carbonate (3.2 g, 23.15 mmol), 4-trifluoromethoxybenzeneboronic acid (3.2 g, 15.54 mmol) and tetrakis(triphenylphosphine)palladium(0) (0.78 g, 0.675 mmol) were added and the reaction mixture heated to reflux under nitrogen overnight. The cooled reaction mixture was then filtered through celite washing through with diethyl ether. The filtrate was dried (MgSO4), filtered and concentrated under reduced pressure. The product was purified using flash chromatography on silica eluting with a solvent gradient of 0 to 100% ethyl acetate in hexanes to give 5-(tert-butyl)-2-hydroxy-4′-(trifluoromethoxy)-[1,1′-biphenyl]-3-carbaldehyde (4.5 g, 85%).
