Acetic Acid → {2-[4-(4-tert-Butoxycarbonylaminobutyl)phenoxy]ethylamino}acetic acid ethyl ester

Participants

Reaction Steps

Dimethylacetone dicarboxylate (1.43 mL, 9.69 mmol) and glacial acetic acid (0.56 mL, 9.70 mmol) were added sequentially to a solution of {4-[4-(2-aminoethoxy)phenyl]-butylcarbamic acid tert-butyl ester (1) (1.0 g, 3.24 mmol) in tetrahydrofuran (20 mL). The reaction was stirred for 2 hours at ambient temperature, then cooled to −30° C. Sodium cyanoborohydride (0.61 g, 9.70 mmol) was added in three portions and the reaction slowly warmed to room temperature over 12 hours. After this time, the reaction was quenched by the addition of water (5 mL). The volatiles was then removed under vacuum to give an oil. This oil was diluted with water (10 mL) and extracted with ethyl acetate (3×10 mL). The combined organics were washed with water (3×10 mL) and then brine (3×10 mL), dried over anhydrous sodium sulfate and concentrated to give 2 (0.576 g, 38% yield) as a clear oil: 1H NMR (500 MHz, CDCl3) δ 1.44 (s, 9H), 1.46-1.52 (m, 2H), 1.55-1.64 (m, 2H), 2.56-2.58 (m, 4H), 2.64-2.65 (m, 2H), 2.72-2.79 (m, 2H), 2.88-2.93 (m, 2H), 3.74 (d, 6H), 3.88-3.93 (m, 1H), 4.44-4.49 (m, 2H), 6.40 (br, 1H), 6.85 (d, 2H), 7.09 (d, 2H); m/z (ESI) 467.

Provenance & Evidence