Acetic Anhydride → 4-[[4-Nitro-3-[(2,4-dioxoimidazolidin-5-ylidene)methyl]phenyl]oxy]butanoic acid

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Reaction Steps

A mixture of ethyl 4-[3-formyl-4-nitrophenoxy]butanoate (2.00 g, 7.1 mmol), hydantoin (0.71 g, 7.1 mmol), and anhydrous sodium acetate (0.58 g, 7.1 mmol) and acetic anhydride (20 mL) was heated at reflux for 1 hour. Upon cooling, H2O was added and the mixture extracted with dichloromethane. The organic portion was washed with water, evaporated, and the residue dissolved in a solution of methanol (20 mL) and 4N NaOH (30 mL). After stirring for 1 hour, the mixture was acidified to pH=2 by addition of 2N HCl. The precipitate was collected and triturated with MeOH/CH2Cl2 to afford 4-[[4-nitro-3-[(2,4-dioxoimidazolidin-5-ylidene)methyl]phenyl]oxy]butanoic acid (0.88 g, 37%). An analytical sample was prepared by crystallization from DMF/H2O to give gold plates, m.p. 181°-184° C.

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