A solution of cesium carbonate (89.12 g, 0.27 mol) in water (600 ml) is added to a degassed solution of (4-bromo-2,6-diethylphenyl)carbamic acid tert-butyl ester (30 g, 0.091 mol) and 4-chlorophenylboronic acid (21.54 g, 0.138 mol) in acetone (3 L), and the mixture is stirred at room temperature under an atmosphere of nitrogen. Palladium acetate (1.02 g, 0.004 mol) and 2-(dicyclohexylphosphino)-2′,4′,6′-tri-iso-propyl-1,1′-biphenyl (4.33 g, 0.009 mol) are added and the reaction mixture is stirred at room temperature for 12 hours. The mixture is filtered through diatomaceous earth, and the filtrate is evaporated under reduced pressure to remove most of the acetone. The remaining solution is extracted with ethyl acetate (3×300 ml). The organic extracts are combined and concentrated under reduced pressure to give (4′-chloro-3,5-diethylbiphen-4-yl)carbamic acid tert-butyl ester (22 g).
