(S)-4-(Phenylmethyl)-2-piperazineethanol synthesis

Yield: 64%

Reaction Conditions:

with lithium aluminium tetrahydride;palladium(II) hydroxide in tetrahydrofuran at -5 - 65; for 18 h;

Steps:

2-[(2S)-4-benzylpiperazin-2-yl]ethanol
Lithium aluminum hydride (13 g, 342.5 mmol) is added to a reaction vessel along with THF (200 mL). The mixture is cooled to -5-0 °C. benzyl 2-[(2S)-4-benzyl-3,6-dioxopiperazin-2-yl]acetate (50 g, 141.9 mmol) is added to a second vessel along with THF (400 mL). The solution of benzyl 2-[(2S)-4-benzyl-3,6-dioxopiperazin-2-yl]acetate is added slowly to the lithium aluminum hydride solution, keeping the temperature between -5 and 0 °C. The reaction mixture is heated to 60-65 °C and stirred for 2 hours. The mixture is cooled to 20-30 °C and stirred for 16 hours. Water (13 g) is added, then 4% NaOH in water (52 g) is added. The mixture is stirred for 1 hour, filtered, and concentrated in vacuo. Isopropyl acetate (200 mL) and 2M HC1 (150 g) are added. The layers are separated and the aqueous layer is washed again with isopropyl acetate (100 mL). The aqueous layer is adjusted to pH 11-12 with NaOH, and DCM (150 mL) is added. The layers are separated and the organic layer is washed with water (100 mL). The layers are separated and the organic layer is concentrated in vacuo to give the title compound as a solid (20.1 g, 64%). 1HNMR (CDCl3) d 7.44 - 7.20 (m, 5H), 3.81 (t, 7 = 5.2 Hz, 2H), 3.50 (s, 2H), 3.08-2.93 (m, 2H), 2.93-2.82 (m, 1H), 2.76 (d, J= 11.5 Hz, 2H), 2.02 (td, J= 11.1, 3.3 Hz, 1H), 1.85 (t, J= 10.4 Hz, 1H), 1.67 -1.52 (m, 2H).

References:

ELI LILLY AND COMPANY WO2021/118877, 2021, A1 Location in patent:Page/Page column 71-72