methyl 5-chloro-4-oxopentanoate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 5-chlorolevulinic acid methyl ester (10 g) in 1-propanol (50 ml) and concentrated sulfuric acid was added (0.5 ml) and the reaction mixture was refluxed for 3 h. Thereafter, the methanol and the excess 1-propanol were distilled in vacuo. Dichloromethane was added to the residue and the organic layer was washed with saturated aqueous sodium hydrogen carbonate and water. Drying of the organic layer with Na2SO4 followed by distillation of the solvent in vacuo yielded 5.4 g (quant.) 5-chlorolevulinic acid propyl ester. The NMR data agreed with the data for the product obtained according to Example 4. the reaction mixture was refluxed for 3 h Thereafter, the methanol and the excess 1-propanol were distilled in vacuo Dichloromethane was added to the residue the organic layer was washed with saturated aqueous sodium hydrogen carbonate and water Drying of the organic layer with Na2SO4 followed by distillation of the solvent in vacuo

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Preparation of 5-chlorolevulinic acid methyl ester from a mixture of 3-chloro-, 5-chloro-, 3,5-dichlorolevulinic acid ethyl ester and levulinic acid methyl ester consisting of the same product ratio, which is obtained by the bromination of both levulinic acid and levulinic acid methyl ester according to the Examples 1 and 2.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In connection with this it is remarkable, that the 5-chlorolevulinic acid methyl ester can be also selectively produced by means of low temperature crystallisation from the chlorination mixture, which you get from the bromination mixture of levulinic acid or levulinic acid methyl ester in methanol and the subsequent bromine/chlorine exchange, in a gentle manner as already described for the 5-bromolevulinic acid methyl ester. As in the case of the 5-bromolevulinic methyl ester you proceed in the same way by using the same solvents and solvent mixtures and temperatures between −20° C. and −40° C. You get the 5-chlorolevulinic acid methyl ester in 35–38% yield and >98 purity. Impurities are the 3-chlorolevulinic acid methyl ester and the unconverted levulinic acid methyl ester. The 5-chlorolevulinic acid esters of the alcohols with chain lengths of C2–C4 can not be produced by low-temperature crystallisation because no crystallisation occurs under these conditions. The same is valid for the corresponding bromination mixtures of the 5-bromolevulinic acid esters which are produced from alcohols with chain lengths of C2–C4. the same solvents and solvent mixtures and temperatures between −20° C. and −40° C

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In connection with this it is remarkable, that the 5-chlorolevulinic acid methyl ester can be also selectively produced by means of low temperature crystallisation from the chlorination mixture, which you get from the bromination mixture of levulinic acid or levulinic acid methyl ester in methanol and the subsequent bromine/chlorine exchange, in a gentle manner as already described for the 5-bromolevulinic acid methyl ester. As in the case of the 5-bromolevulinic methyl ester you proceed in the same way by using the same solvents and solvent mixtures and temperatures between −20° C. and −40° C. You get the 5-chlorolevulinic acid methyl ester in 35–38% yield and >98 purity. Impurities are the 3-chlorolevulinic acid methyl ester and the unconverted levulinic acid methyl ester. The 5-chlorolevulinic acid esters of the alcohols with chain lengths of C2–C4 can not be produced by low-temperature crystallisation because no crystallisation occurs under these conditions. The same is valid for the corresponding bromination mixtures of the 5-bromolevulinic acid esters which are produced from alcohols with chain lengths of C2–C4. can be also selectively produced by means of low temperature crystallisation from the chlorination mixture, which you

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In EP 58392 a procedure for the production of 5-chlorolevulinic acid ethyl ester is described that starts from succinic acid mono ethyl ester mono chloride. This compound is converted with diazo methane at −5° C. and is after that worked up by passing in hydrogen chloride. You receive so the desired compound in pure form and in a high yield but the difficult handling of explosive diazo methane makes this method for the large-scale use not suitable. The same procedure is described in PL 136454. Instead of the succinic acid mono ethyl ester mono chloride the respective methyl ester derivative is used and results in the formation of 5-chlorolevulinic acid methyl ester. in a high yield