General procedure for the synthesis of 3,5-dichlorobenzonitrile from 3,5-dichloro-1-bromobenzene: iPrMgCl (2M in THF, 4.1 mL) and THF (5 mL) were added to a flask containing dry LiCl (0.35 g, 8.24 mmol) at 15 °C. After stirring for 15 min, a solution of 3,5-dichloro-1-bromobenzene (1.46 g, 8.03 mmol) in THF (1 mL) was slowly added to the reaction mixture and stirring was continued for 15 min. Subsequently, the reaction mixture was cooled to 0 °C, DMF (1.3 mL, 12 mmol) was added and stirred at this temperature for 2 hours. Upon completion of the reaction, aqueous NH3 (7 mL, 28-30%) and I2 (4.06 g, 16 mmol) were sequentially added to the mixture. After stirring for 2 h at room temperature, the reaction mixture was poured into saturated aqueous Na2SO3 solution and extracted with CHCl3 (3 x 30 mL). The organic layers were combined, dried with Na2SO4 and filtered. After removing the solvent under reduced pressure, the residue was purified by silica gel column chromatography (eluent: hexane/ethyl acetate = 9:1, v/v) to afford pure 3,5-dichlorobenzonitrile (0.73 g) in 71% yield. Most of the nitrile compounds involved in this study were commercially available and were identified by comparison with real samples.
