Condensation of 2-acetoxybenzaldehyde with malonic acid and ethyl malonate

P. M. Bhargava & S.H. Zaheer

Published in: Journal of the Chemical Society, 1952, Part I, 311-313

Abstract:

Condensation of o-acetoxybenzaldehyde with malonic acid or ethyl malonate, in presence of pyridine, involves partial ring-closure to coumarin derivatives. Some aryl esters of coumarin-3-carboxylic acid have been shown to have no insecticidal action on house-flies.

The pyridine-catalysed condensation of salicylaldehyde with malonic acid or ethyl malonate gives respectively coumarin-3-carboxylic acid and its ethyl ester (Knoevenagel, Ber., 1898, 31, 2596; Kurien, Pandya, and Surange, J. Indian Chem. Soc., 1934, 11, 823; Khan, Kurien, and Pandya, Proc. Indian Acad. Sci., 1935, 1, A, 440; Knoevenagel and Hoffmann, Ber., 1898, 31, 2593; Kurien, Peter, and Pandya, Proc. Indian Acad. Sci., 1935, 1, A, 775; Horning, Horning, and Dimmit, Org. Synth., 1948, 28, 24). We have now found that replacement of this aldehyde by its acetyl derivative leads, with malonic acid to coumarin-3-carboxylic acid (38.7%) and 2-acetoxycinnamic acid (28%}, and with ethyl malonate to ethyl coumarin-3-carboxylate (45.1 %) and ethyl salicylidenemalonate (37%). It is interesting that a molecule of ethyl alcohol is not eliminated from the malonic ester during the condensation.

Ethyl salicylidenemalonate yielded coumarin-3-carboxylic acid on hydrolysis with acid, and with concentrated aqueous ammonia, gave the ester-amide which is also hydrolysed to coumarin-3-carboxylic acid by mineral acid. Ethyl salicylidenemalonate with acetyl chloride and pyridine, or with acetic anhydride and anhydrous sodium acetate, gave ethyl coumarin-3-carboxylate. These reactions prove the structure assigned to the salicylidenemalonate.

During this work, some aryl esters of coumarin-3-carboxylic acid were prepared. These had no insecticidal action on house-flies.

HOW TO CITE

Condensation of 2-acetoxybenzaldehyde with malonic acid and ethyl malonate. P M BHARGAVA & S H ZAHEER. Journal of the Chemical Society, 1952, Part I, 311-313.

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