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Similarly, the other acylated-5-(substituted benzal) hydantoins can be prepared by heating the appropriately substituted benzaldehyde and an anhydrous alkali metal alkanoate together with hydantoin and the corresponding acid anhydride. The reaction is generally conducted at an elevated temperature until the reaction is substantially complete. For example, in the reaction of benzaldehydes with hydantoin in the presence of anhydrous sodium acetate and acetic anhydride, the reaction is generally carried out at about 125°-140° C. it has also been found that potassium bicarbonate can be used in place of the anhydrous alkali metal alkanoate with similar results being obtained. After the condensation is complete, the reaction mixture is cooled, usually overnight, treated with water and then refrigerated for several hours. The crystalline product is then filtered, washed with water and dried. The major portion of the product appears to be the mono-acylated compound, together with small amounts of di-acylated compound. Where the aromatic aldehyde starting material contains phenolic hydroxylic groups, it has been found that these are acylated under the conditions of the reaction. Thus protocatechualdehyde, hydantoin, anhydrous sodium acetate, and acetic anhydride gave acetylated 5-(3',4'-diacetoxybenzal) hydantoin.

1. customis generally carried out at about 125°-140° C.
2. customwith similar results
3. custombeing obtained
4. temperaturethe reaction mixture is cooled, usually overnight
5. waitrefrigerated for several hours
6. filtrationThe crystalline product is then filtered
7. washwashed with water
8. customdried
9. customthese are acylated under the conditions of the reaction