[Synthesis]
2-Methyl-2,3-dihydro-1H-indene-2-carboxylic acid (1.63 g, 9.26 mmol) was dissolved in acetone (15 mL), stirred and cooled to 0°C. To this cooled solution was sequentially added triethylamine (1.47 mL, 10.46 mmol) and ethyl chloroformate (1.00 mL, 10.46 mmol). The reaction mixture was stirred continuously at 0 °C for 40 min. Subsequently, a solution of sodium azide (903 mg, 13.89 mmol) in water (5 mL) was added slowly and dropwise over 1 min and stirring was continued for 1 h at 0°C. Upon completion of the reaction, the cooled suspension was partitioned between ethyl acetate and saturated brine, and the aqueous layer was extracted with additional ethyl acetate. The organic layers were combined and dried with anhydrous magnesium sulfate, followed by evaporation of the solvent to give an oily intermediate. This oily substance was dissolved in toluene (10 mL), heated to 100 °C and maintained for 20 min until nitrogen stopped escaping. After removing the solvent, the residue was dissolved in 5 M hydrochloric acid (20 mL) and heated to reflux overnight. After cooling, the reaction mixture was diluted with water and the insoluble material was extracted with ethyl acetate. The organic layer was again dried with anhydrous magnesium sulfate and evaporated to recover unreacted material (550 mg, 34%). The aqueous phase was evaporated to dryness under reduced pressure to afford the target product 2-methyl-2,3-dihydro-1H-inden-2-amine hydrochloride as a white powder (870 mg, 51%). The product was characterized by 1H-NMR (400 MHz, DMSO-d6): δ 8.42 (3H, broad single peak), 7.26 (2H, multiple peaks overlapping), 7.19 (2H, multiple peaks overlapping), 3.20 (2H, double peaks, J = 16.4 Hz), 2.99 (2H, double peaks, J = 16.4 Hz), 1.44 (3H, single peaks). |