反应详情

A solution of ethyl 4-phenyl-2-oxobutanoate (2.06 g; 10 mmol) and t-butylcarbazate (1.32 g; 10 mmol) in THF (50 ml) can be warmed at reflux for 8 hours. Solvent can be evaporated and the residue taken up in anhydrous ethanol (25 ml). Sodium cyanoborohydride (0.31 g; 5 mmol) can be added, and the solution stirred for 4 hrs. The residue, after evaporation, can be stirred with EtOAc (50 ml) and hydrochloric acid (0.5 N: 20 ml) for 30 minutes. The aqueous layer can be neutralized by addition of K2CO3 and extracted with EtOAc (3×25 ml). The combined organic portions can be washed with H2O and brine and dried (MgSO4). The residue, upon evaporation, can be purified by chromatography on silica gel, affording N-(1-carboethoxy-3-phenylpropyl)-N'-BOC-hydrazine. An ice-cold solution of the above hydrazine in trifluoroacetic acid can be allowed to stand for 1 hr. Removal of solvent can provide hydrazine (56) as the trifluoroacetic acid salt.

1. customRemoval of solvent