Synthesis of (4Z)-4-benzylidene-5-methyl-2-phenylpyrazol-3-one

To a reflux apparatus with a Dean-Stark trap add 4 g of edaravone, 2.6 mL of benzaldehyde, 50 mL of toluene and 0.5 g of p-toluene sulfonic acid, the mixture is refluxed strongly with stirring for 3h, thereafter the solution is cooled down. The solution is then washed with 50 mL of cold dilute sodium carbonate solution and twice with cold 50 mL of water. The red organic layer is then evaporated to dryness and recrystallized twice from hot ethanol.

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The chemicals combined

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Refluxing the mixture

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The Dean-Stark trap

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The recrystallized product

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