Triethylamine → [(4-Methoxyphenyl)hydrazono]acetic acid ethyl ester

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A suspension of 4-methoxy-phenylhydrazine hydrochloride (32, 14.0 g, 80.2 mmol) in anhydrous THF (100 mL) was treated with triethylamine (TEA, 8.10 g, 11.2 mL, 80.2 mmol, 1.0 equiv) before a solution of ethylglycolate (50% solution in toluene, 16.4 g, 80.2 mmol, 1.0 equiv) in toluene was dropwise added into the reaction mixture at 0-5° C. under N2. The resulting reaction mixture was then stirred at 0-5° C. for 30 min before being gradually warmed to 25° C. for 12 h. When TLC and HPLC showed the reaction was deemed complete, the reaction mixture was filtered to collect triethylamine hydrochloride salt. The filtrates were concentrated in vacuo, and the resulting solids were collected by filtration. The crude solids were washed with water (2×50 mL) and 20% of EtOAc/hexane (2×50 mL), and dried at 40-45° C. in vacuo for 12 h to afford the crude, desired [(4-methoxyphenyl)hydrazono]acetic acid ethyl ester (33, 16.0 g, 17.80 g theoretical, 90%), which was found to be pure enough to do the following reaction without further purification. For 33: CIMS m/z 221 (M+−H, C11H14N2O3).

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