Pseudoephedrine → N-(2-hydroxy-1-methyl-2-phenylethyl)-N-methyl hexanamide

Temperatur

23 °C

In a dry 2 L round-bottomed flask equipped with a magnetic stirrer was added (+)-pseudoephedrine (40.0 g, 242.06 mmol, 1.0 equiv) and tetrahydrofuran (500 mL), and the mixture was stirred in a 23° C. water bath. Hexanoic anhydride (55.51 g, 259 mmol, 1.07 equiv) was added via cannula over a 10 minute interval, and transfer was quantitated with an additional portion of tetrahydrofuran (10 mL). After 25 minutes, the reaction was quenched with saturated sodium bicarbonate (300 mL). Volatile components were removed under reduced pressure, and the residue was extracted from water (500 mL) with ethyl acetate (3×250 mL). The organic extracts were dried over sodium sulfate, and after removal of the solvent under reduced pressure, a white solid was obtained, which was recrystallized from 1:1 ether/hexanes (200 mL) to afford the hexanamide as white crystals (58.2 g, 91% yield): mp 62°-63° C.; 1H NMR (300 MHz, C 6D6) δ7.0-7.4 (m, 5H), 4.9 (br, 1H), 4.52 (d, 1H, J=6.9 Hz), 4.14 (m, 1H), 3.77 (m, 1H), 2.79 (s, 3H), 2.42 (m, 2H), 2.13 (s, 3H), 1.83 (m, 2H), 1.59 (qn, 2H, J=7.6 Hz), 1.1-1.4 (m, 4H), 0.99 (d, 3H, J=7.0 Hz), 0.86 (t, 3H, J=7.0 Hz), 0.59 (d, 3H, J=6.8 Hz); 13C NMR (75.5 MHz, CDCl3) δ175.2, 174.2, 142.3, 141.6, 128.3, 128.0, 127.8, 127.3, 126.7, 126.2, 76.1, 75.1, 58.2, 57.0, 34.1, 33.4, 32.4, 31.5, 31.3, 26.6, 24.9, 24.5, 22.31, 22.29, 15.2, 14.2, 13.82, 13.79; FTIR (neat film) cm-1 3378 (br, m), 2956 (m), 2931 (m), 2871 (m), 1618 (s), 1453 (m), 1406 (m), 1051 (m), 701 (m); HRMS (FAB) Calcd for C16H26N02 (MH+): 264.1965. Found: 264.1966.