反应详情

A solution of [(4-chlorophenyl)hydrazono]acetic acid methyl ester (30, 13.0 g, 61.2 mmol) in anhydrous THF (100 mL) was treated with N-bromosuccinimide (NBS, 11.97 g, 67.3 mmol, 1.1 equiv) at 0–5° C. under N2, and the resulting reaction mixture was stirred at 0–5° C. for an additional 30 min. When HPLC and TLC showed the reaction was deemed complete, the solvent removed in vacuo. The residue was directly purified by column chromatography (SiO2, 0–15% EtOAc/hexane gradient elution) to afford the desired bromo[(4-chlorophenyl)hydrazono]acetic acid methyl ester (31, 15.0 g, 17.84 g theoretical, 84%) as pale-yellow solids, which was found to be essentially pure to do the following cycloaddition reaction without further purification. For 31, CIMS m/z 290/292 (M+−H, C9H8BrClN2O2).

1. customthe resulting reaction mixture
2. customthe solvent removed in vacuo
3. customThe residue was directly purified by column chromatography (SiO2, 0–15% EtOAc/hexane gradient elution)