p-Toluenesulfonic acid → 3-Amino-1-(3-bromo-4-chlorobenzyl)-pyrazol-5-one

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Reaction Steps

49 g of β-amino-β-ethoxyacrylic acid ethyl ester and 2 g of p-toluenesulphonic acid were dissolved in 225 ml of ethanol and 72 g of 3-bromo-4-chlorobenzylhydrazine were added under nitrogen. After standing overnight, the compound identified above had settled out as a precipitate and was filtered off and recrystallised twice from ethanol. Melting point: 171°-172°C, 40 g (43%).

Provenance & Evidence