Aluminium lithium hydride → (S)-2-(4-benzylpiperazin-2-yl)ethanol

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Reaction Steps

To a 0° C. solution of (S)-(4-benzyl-3,6-dioxopiperazin-2-yl)acetic acid methyl ester (31.9 g, 0.12 mol) in tetrahydrofuran (1 L), add lithium aluminum hydride via slow cannulation (350 mL of a commercial 1.0 M solution in tetrahydrofuran). Stir at room temperature overnight, quench by successive careful addition of 13.3 mL of water, 13.3 mL of 15% aqueous sodium hydroxyde, and 39.9 mL of water, all the while with vigourous stirring to ensure formation of a fine precipitate. Filter through a fritted funnel, washing the solids well with tetrahydrofuran and dichloromethane. Concentrate in vacuo to provide 26.5 g of an oily residue, apply directly to a silica gel column. Elute with a 5% mixture of 7N ammonia-methanol in dichloromethane, to obtain the desired product as an orange oil which solidifies under vacuum. Take up the solid in acetonitrile and sonicate for a few minutes. Filter the resulting precipitate to obtain 7.5 g (25%) of the title compound as an off-white crystalline solid, mp 78.9-80.4° C. Concentrate the mother liquor to obtain 6.8 g (23%) of slightly less pure material as an amorphous solid: mass spectrum (ES): m/e 221.3 (M+1); specific Rotation: −7.84.

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