GB636287A - Improvements in preparation of keto-carboxylic acids and their derivatives - Google Patents

Abstract

Keto-acids or their derivatives are obtained by reacting aldehydes with olefinic carboxylic acids or their derivatives in the presence of a source of free radicals, the aldehyde being a n-alkanal, sec-alkanal, cycloalkane-aldehyde, aralkanal or aromatic aldehyde; when an unsaturated acid is used, the corresponding keto-acid is formed, and when a hydrolysable derivative of the acid is used, the corresponding derivative of the keto-acid is formed. The source of free radicals may be ultra-violet rays, which produce the radicals by photochemical action on the reaction mixture, or a catalyst which yields free radicals at the reaction temperature. Preferred catalysts are organic peroxides such as dibenzoyl peroxide; others are hydrogen peroxide, organic hydroperoxides, inorganic per-salts, hydrazine compounds (organic and inorganic) and organo-metallic compounds, but not Friedel-Craft catalysts; suitable compounds are mentioned. An inert diluent may be present. Suitable aldehydes, olefinic acids and their derivatives are given, the latter including esters, nitriles, amides, anhydrides and halides. Preferred olefinic compounds are those where the double bond is at the end of the chain and/or in the alpha position to the carboxyl group or its derivative and where at least one of the doubly-linked carbon atoms has a hydrogen atom attached thereto. The products have the formula R-CO-(X)n-H, where RCHO is the aldehyde used, X is the divalent radical obtained by opening the double linkage of the olefinic compound, and n is an integer from 1 to 5, depending on the proportions of reactants used, the aldehyde preferably being always present at least in an equimolecular amount. The reaction temperature may be from 25 DEG to 150 DEG C. preferably 60 DEG to 100 DEG C., using super-atmospheric pressure if the reactants have too low a boiling point. The products may be isolated by fractional distillation or fractional crystallization of the reaction mixture. Examples show the production of (1) diethyl a -butyro-succinate from diethyl maleate and n-butyraldehyde; alkaline hydrolysis of the product yields 4-keto-heptanoic acid; (2) diethyl a -butyro-succinate from diethyl furmarate and n-butyraldehyde; (3) 12-keto-tridecanoic acid from 10-hendecenoic acid and acetaldehyde; the product may be converted into its semicarbazone; (4) methyl 12-ketotridecanoate from methyl undecylenate and acetaldehyde; (5) methyl 4-keto-heptanoate from methyl acrylate and n-butyraldehyde; the product yields a 2 : 4-dinitrophenylhydrazone.