GB603422A - Process for the hydrolysis of 2, 5-dihydrofurans - Google Patents

Abstract

Unsaturated dicarbonyl compounds of the general formula R1CO.CH=CHCOR2, where R1 and R2 represent hydrogen, alkyl and carboxylic ester groups, are prepared by hydrolysing, in aqueous medium, 2 : 5-dihydrofurans of the general formula <FORM:0603422/IV(b)/1> where R1 and R2 have the above significance and R3 and R4 represent saturated or unsaturated aliphatic, alicyclic or aliphatic-alicyclic groups, e.g. groups containing up to ten carbon atoms or, preferably, alkyl groups containing up to four carbon atoms. The hydrolysis may be effected either while cooling the reaction mixture or at atmospheric temperature. An acid, e.g. a non-oxidizing acid such as hydrochloric acid, may be present during the reaction, if necessary at a low concentration. The unsaturated dicarbonyl compound may be separated by extracting the reaction medium with an organic solvent, drying the extract, distilling off the solvent and fractionally distilling the residue. Compounds of the general formula <FORM:0603422/IV(b)/2> where R1, R2, R3 and R4 have the significance already indicated, are stated to be formed as intermediate products. In examples: (1) maleic dialdehyde is prepared by shaking water and 2 : 5 - dimethoxy - 2 : 5 - dihydrofuran; (2) 2 : 5 - dimethoxy - 2 : 5 - dihydrofuran, water and hydrochloric acid are shaken, extracted with ether, the extract dried, the ether removed by distillation and the residue fractionated to yield maleic dialdehyde. The preparation of the following dicarbonyl compounds is also mentioned: maleic dialdehyde from 2 : 5-dicyclohexyloxy - 2 : 5 - dihydrofuran or 2 : 5 - diallyloxy - 2 : 5 - dihydrofuran, b -acetylacrolein from 2 : 5 - dimethoxy - 2 : 5 - dihydrosylvan, a b -diacetyl ethylene from 2 : 5-dimethyl-2 : 5-dimethoxy-2 : 5-dihydrofuran, and (21-formylvinyl) - 1 - keto - acetic methyl ester from 2 : 5 - dimethoxy-2 : 5-dihydromethylfuroate-2. The Provisional Specification refers also to the preparation of dicarbonyl compounds of the above general formula, where in addition R1 and R2 represent alkoxy and carboxylic groups, by the hydrolysis of 2 : 5-dihydrofurans of the above general formula, where in addition R3 and R4 represent aromatic or substituted aromatic groups.