1-Chloroethyl chloroformate → 1-(3-Chloro-2-pyrazinyl)-2-ethylpiperazine, Hydrochloride

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Reaction Steps

1-Chloroethyl chloroformate (2.11 g, 15.2 mmol) was added with a syringe during 1 h to an ice cold (˜0° C.) solution of 4-benzyl-1-(3-chloro-2-pyrazinyl)-2-ethylpiperazine (3.22 g, 10.1 mmol, from Step 2) in dry CH2Cl2 (30 mL). The reaction was allowed to slowly reach room temperature and stirred for 48 h. The solvent was evaporated from the reaction mixture and MeOH was added to the resulting oil. The mixture was heated to reflux for 2 h, the solvent was evaporated and the resulting oil was partitioned between CHCl3/H2O. The aqueous phase was made alkaline and extracted with CHCl3 (×3). Tie combined organic phases were dried (MgSO4), and the solvent was evaporated. The resulting oil was purified by column chromatography on silica using CHCl3/MeOH/NH4OH (95:5:0.2) as eluent to give a quantitative yield (2.35 g) of the free base of the title compound as a slightly yellow oil. An analytical sample was prepared as its hydrochloric acid salt (from HCl/ether): mp 195-197° C. Anal. (C10H15ClN4.HCl) C, H, N.

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