General procedure for the synthesis of benzodihydropyran-4-ylamine from 2,3-dihydrochromen-4-one: 2,3-dihydrochromen-4-one (3 g, 20.1 mmol), titanium(IV) isopropoxide (12.0 mL, 40.2 mmol), and an ethanol solution of 2 M ammonia (60.6 mL, 121.2 mmol) were mixed and stirred at room temperature for 6 hours. Subsequently, the reaction mixture was cooled to 0 °C and sodium borohydride (1.14 g, 30.2 mmol) was added in batches over 10 min. The resulting mixture was continued to be stirred at room temperature for 3 hours. Upon completion of the reaction, the reaction was quenched by pouring the mixture into 2 M ammonium hydroxide solution (60 mL), the precipitate formed was filtered out and washed with ethyl acetate (15 mL x 3). The organic layer was separated and the remaining aqueous layer was further extracted with ethyl acetate (15 mL x 2). The organic extracts were combined and washed with 1 M HCl (25 mL). The acidic aqueous layer was washed with ethyl acetate (50 mL), adjusted to pH 10-12 with 2M aqueous sodium hydroxide and extracted with ethyl acetate (40 mL × 3). The organic extracts were combined, washed with brine, dried over anhydrous sodium sulfate and concentrated in vacuum to give benzodihydropyran-4-ylamine as an oil (2.61 g, 87% yield). The product was characterized by 1H NMR (400 MHz, CDCl3): δ 7.31 (d, 1H), 7.23 (m, 1H), 6.94 (m, 1H), 6.82 (d, 1H), 4.38 (m, 2H), 4.12 (m, 1H), 2.19 (m, 2H), 1.82 (m, 2H).
