Ethyl Acetate → 7-Chloro-8-methyl-1,2,3,4-tetrahydropyrazino[1,2-a]indole

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Reaktionsschritte

Ethyl 6chloro-1-(cyanomethyl)-5-methylindole-2-carboxylate (1.75 g, 6.3 mmol) was added portionwise over 2 min to a stirred solution of lithium aluminium hydride (0.61 g, 16 mmol) in ether (50 mL) at room temperature under Ar. The reaction was then heated to reflux and stirred for 70 h. The mixture was cooled to room temperature, a further portion of lithium aluminium hydride (0.61 g) was added and the reaction was heated to reflux and stirred for 18 h. The mixture was allowed to cool and then poured into aqueous potassium sodium tare solution (200 mL) and ethyl acetate (150 mL). The mixture was filtered through celite and the aqueous and organic layers were separated. The aqueous was extracted with ethyl acetate (2×100 mL) and the combined organic extracts were washed with brine (1×100 mL) dried (magnesium sulfate), filtered and the solvent removed under vacuum to leave a crude oil. The oil was purified by flash column chromatography [SiO2; ethyl acetate-methanol, (100:0)→(9:1)] to give the product as a yellow solid (027 g, 19%). IR νmax (Nujol)/cm−1 3351, 3190, 2922, 2731, 1734, 1647, 1615, 1562, 1543, 1457, 1416, 1378, 1350, 1316, 1304, 1261, 1246, 1223, 1182, 1157, 1134, 1116, 1028, 983, 972, 962, 902, 883, 835, 800, 782, 732, 700, 666, 632, 617, 558, 510 and 496; NMR δH (400 MHz; CDCl3) 7.35 (1H, s), 725 (1H, s), 6.06 (1H, m), 4.16 (2H, s), 3.91 (2H, t, J 5.5 Hz), 3.31 (2H, t, J 5.5 Hz), 2.42 (3H, s).

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