General procedure for the synthesis of 5-aminoindan from 5-nitroindene: To a solution of EtOAc (20 mL) of 5-nitroindene (80.5 mg, 0.5 mmol) was added 10% Pd/C (catalyst dosage of 20% by mass of 5-nitroindene). The mixture was stirred overnight at room temperature in a hydrogen atmosphere. Upon completion of the reaction, the insoluble material was removed by filtration and washed with EtOAc. The filtrate was concentrated to dryness under reduced pressure to give 5-aminoindene (65 mg, 98% yield) as a brown oil. To a solution of 5-aminoindene (150 mg, 0.8 mmol) in thionyl chloride (4 mL) was added a drop of pyridine followed by reflux for 24 hours. At the end of the reaction, the thionyl chloride was removed by distillation to give 5-aminoindene chloride as a light yellow solid, and the product was used directly in the next step of the reaction. A dichloromethane (2 mL) solution of 5-aminoindene chloride was added dropwise to an anhydrous pyridine (2 mL) solution of 5-aminoindene (65 mg, 0.5 mmol) at 0°C. The mixture was stirred at room temperature for 7 h. Methanol was subsequently removed by distillation. The organic layer was treated sequentially with 1N HCl until acidic. The mixture was partitioned between water and EtOAc. The organic layer was washed with saturated brine, dried over anhydrous Na2SO4 and concentrated in vacuum. The residue was purified by silica gel column chromatography (eluent: hexane/EtOAc = 3/1) to afford the target compound 5-aminoindan (118 mg, 80% yield) as a light yellow solid. Melting point 138~142°C; 1H-NMR: δ8.15 (d, J=6.9Hz, 2H), 7.93 (d, J=8.1Hz, 2H), 7.60 (s, 1H), 7.30 (d, J=8.1Hz, 1H), 7.22 (d, J=7.9Hz, 1H), 3.96 (s, 3H), 2.95-2.89 (m. 4H), 2.13-2.07 (m, 2H); ESI-MS: m/z [M+H]+ 296.
