Ammonia → 3,4-Dihydro-2H-1-benzopyran-4-amine

Participants

Reaction Conditions

Reaction Steps

Chroman-4-one (3 g, 20.1 mmol), titanium(IV) isopropoxide (12.0 mL, 40.2 mmol) and 2 M solution of ammonia in ethanol (60.6 mL, 121.2 mmol) were stirred at room temperature for 6 h. The reaction was cooled to 0° C. and sodium borohydride was added portionwise during 10 min (1.14 g, 30.2 mmol); the resultant mixture was stirred at rt for an additional 3 h. The reaction was quenched by pouring it into ammonium hydroxide (2 M, 60 mL), the precipitate that formed was filtered off and washed with ethyl acetate (15 mL×3). The organic layer was separated and the remaining aqueous layer was extracted with ethyl acetate (15 mL×2). The combined organic extracts were washed with 1 M HCl (25 mL). The acidic aqueous extracts were washed with ethyl acetate (50 mL), then treated with aqueous sodium hydroxide (2 M) to pH 10-12, and extracted with ethyl acetate (40 mL×3). The combined organic extracts were washed with brine, dried (Na2SO4), and concentrated in vacuo to afford Chroman-4-amine as an oil (2.61 g, 87% yield). 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).

Provenance & Evidence