Patent GB-1081234-A (GB)
Title: Process for the production of keto carboxylic acids
Inventor: HAAGE KLAUS
IPC: C07C51/373
Filed: 1966-03-14
Abstract: Keto-carboxylic acids and/or the saturated and unsaturated lactones of the corresponding hydroxy-carboxylic acids are obtained by reacting the anhydride of a saturated or unsaturated, unsubstituted or substituted, aliphatic or aromatic dicarboxylic acid with an alkyl aluminium compound of the general formula RnAlX3- n in which R is an aliphatic, araliphatic, cycloaliphatic or aromatic radical, X is a halogen atom and n is 1 to 3 and then hydrolysing the reaction mixture with aqueous mineral acid.  The reaction may be carried out by direct or inverse addition optionally in the presence of a suitable solvent with the exclusion of air or moisture and, if desired, replacing a specified portion of the alkyl aluminium compound with an anhydrous aluminium tri-halide. The process yields mainly the keto-carboxylic acid at temperatures less than +20 DEG C., whereas the proportion of lactones formed is increased, particularly when mixtures of tri-alkyl aluminium compounds and aluminium trihalides are employed, at temperatures greater than +20 DEG . The desired products are isolated by conventional means. The preferred di-carboxylic anhydrides are those of succinic, glutaric, maleic or phthalic acids.  The use of ethyl aluminium sesquihalide, iso-butyl, n-hexyl and n-octyl aluminium dichloride and tri-ethyl and trihexyl aluminium optionally in the presence of anhydrous aluminium chloride is exemplified. g -Keto-caproic acid with the lactones of 4-hydroxyhexanoic and 4-hydroxyhex-3-enoic acids, g -keto-capric and g -keto-lauric acid are obtained by reacting succinic anhydride with ethyl aluminium sesquihalide and n-hexyl and n-octyl-aluminium dichloride respectively. d -Keto-oenanthic acid with the lactone of d -hydroxyoenanthic acid, and o-propionylbenzoic acid are prepared by reacting ethyl aluminium sesquichloride with glutaric and phthalic anhydrides respectively.  b -Propionylacrylic acid with a mixture of lactones of 4-hydroxyhex-2-enoic acid and 4-ethyl-4-hydroxyhex-2-enoic acids, b -nonanoyl-acrylic acid with the lactone of 4-hydroxydodec-2-enoic, and a mixture of lactones related to 4-ketohept-2-en-1-oic acid (i.e. lactones of 6-methyl-4-hydroxyheptanoic and 6-methyl-4-hydroxyhept-2-enoic acids) are obtained by reacting maleic anhydride with ethyl aluminium sesquihalide, n-octyl- and isobutyl-aluminium dichloride respectively.  Mixtures of lactones corresponding to g -keto-caproic acid (i.e. lactones of 4-hydroxyhexanoic and 4-hydroxyhex-3-enoic acids) and to g -keto-capric acid (i.e. lactones of 4-hydroxydodecanoic and 4-hydroxydodec-2-enoic acids) are prepared by reacting succinic anhydride with tri-ethyl aluminium and tri-hexyl aluminium respectively while lactones related to b -propionylacrylic acid (i.e. lactones of 4-hydroxyhex-2-enoic and 4-ethyl-4-hydroxyhex-2-enoic acids) are obtained by reacting maleic anhydride with ethyl aluminium sesquichloride.  Unspecified g -keto-acids and related lactones are also prepared from succinic anhydride and an addition product of triethyl aluminium and ethylene.