To a solution of 4-(4-chlorophenyl)-3-(3-bromophenyl)-2-butanol (1.5 kg, 4.6 mol) in dimethylformamide/water (volume ratio 99:1, 15 L total) was added zinc cyanide (0.39 kg, 3.3 mol), 1,1′-bis(diphenylphosphino)ferrocene (115 g, 0.21 mol) and tris(dibenzylideneacetone)dipalladium (76 g, 0.08 mol). The reaction mixture was stirred and degassed at room temperature for 1 h, and heated at 115° C. for 6 h before cooling to room temperature. Tributylphosphine (46 mL, 0.17 mol) was then added. After stirring for 1 h, the reaction was quenched with aqueous ammonia (1.56 L). After stirring for 1 h, the mixture was filtered through solka floc, and the cake was washed with isopropyl acetate. The filtrate was washed with water (5 L), and the aqueous layer was extracted with isopropyl acetate (4 L). The organic layers were combined, washed with water (10 L×2) and concentrated to give the title compound, which was used for the ensuing reaction after azeotroping with toluene.
