Synthesis
Under cooling conditions in an ice bath, 1.19 g of dihydroindole was dissolved in 10 ml of toluene and 5.5 ml of 2.02 M toluene solution of boron trichloride was slowly added. The reaction mixture was refluxed in an oil bath for 1 hour. After completion of the reaction, the solvent was removed by evaporation at atmospheric pressure. The residue was mixed with 2 mL of trichloroacetonitrile and heated in an oil bath at 60°C to 62°C for 20 hours. At the end of the reaction, the product was dissolved in 20 ml of dichloromethane and slowly poured into 40 ml of methanol solution containing 9.1 g of potassium carbonate under cooling in an ice bath. The mixture was refluxed in an oil bath for 1 hour, followed by filtration to remove insoluble material. The filtrate was evaporated and the residue was partitioned between water and dichloromethane. The dichloromethane layer was washed with dilute hydrochloric acid, dried over anhydrous magnesium sulfate and evaporated to dryness. The residue was purified by Lobar column chromatography to give 1.10 g of crude product. 0.913 g of the product was crystallized from dichloromethane and recrystallized with ether-hexane to give 0.836 g of 7-cyanodihydroindole with a melting point of 66-67 °C. Elemental analysis results (C9H8N2): calculated values (%): C, 74.97; H, 5.59; N, 19.43; measured values (%): C, 74.98; H, 5.60; N, 19.51. IR spectrum (CHCl3): 3432, 2217 cm-1.
