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

Synthesis

General procedure for the synthesis of 2-[(S)-4-benzyl-2-yl]ethanol from the compound (CAS:612506-99-7): to a tetrahydrofuran (1L) solution of methyl S-(4-benzyl-3,6-dioxopiperazin-2-yl)acetate (31.9 g, 0.12 mol) at 0 °C, lithium aluminum hydride (350 mL, 1.0 M tetrahydrofuran solution). The reaction mixture was stirred overnight at room temperature. Subsequently, the reaction was quenched by successive careful addition of 13.3 mL of water, 13.3 mL of 15% aqueous sodium hydroxide solution and 39.9 mL of water, during which vigorous stirring was maintained to ensure the formation of a fine precipitate. The reaction mixture was filtered through a sintered funnel and the solid fraction was washed well with tetrahydrofuran and dichloromethane. The filtrate was concentrated under vacuum to give 26.5 g of an oily residue which was directly sampled on a silica gel column. Column chromatographic separation was carried out using a 5% 7N ammonia-methanol dichloromethane mixture as eluent to obtain the target product, which was an orange-colored oil and solidified to a solid after vacuum drying. This solid was dissolved in acetonitrile, sonicated for several minutes and filtered to give 7.5 g (25% yield) of S-(-)-2-(4-benzylpiperazin-2-yl)ethanol as an off-white crystalline solid with a melting point of 78.9-80 °C. The mother liquor was concentrated to give 6.8 g (23% yield) of a slightly less pure product as an amorphous solid.

References

[1] Patent: WO2003/82877, 2003, A1. Location in patent: Page/Page column 96-97
[2] Patent: WO2005/26177, 2005, A1. Location in patent: Page/Page column 91-92
[3] Patent: WO2004/14895, 2004, A1. Location in patent: Page 125-126