Process for the manufacture of 2,6-dimethyl-5-hepten-1-al

Abstract

The present invention relates to an improved process for the manufacture of 2,6-dimethyl-5-hepten-1-al.

Claims

1. A process for the manufacture of the compound of formula (I): ##STR00010## wherein the process comprises the steps of: (i) conducting a step (ia) by carrying out a Darzens reaction with a compound of formula (II): ##STR00011## and a compound of formula (III): ##STR00012## wherein X is Cl or Br, in the presence of NaOR, wherein R is a C.sub.1-4-alkyl, and in the presence of at least one hydrocarbon solvent selected from the group consisting of cyclohexane, n-hexane, n-heptane, benzene, o-xylene, m-xylene, p-xylene and toluene, followed by conducting a step (ib) by carrying out a saponification reaction to form the compound of formula (V): ##STR00013## and thereafter (ii) subjecting the compound of formula (V) to a decarboxylation reaction to form the compound of formula (I).

2. The process according to claim 1, wherein the reaction temperature of step (ia) is 15 C.

3. The process according to claim 1, wherein step (ib) is carried out at a reaction temperature in the range of from 30 C. to 60 C.

4. The process according to claim 1, wherein step (ii) is carried out at a reaction temperature of at least 160 C.

5. The process according to claim 1, wherein step (ii) is carried out in the absence of a metal powder.

6. The process according to claim 5, wherein step (ii) is carried out in the absence of a copper powder.

7. The process according to claim 2, wherein the reaction temperature of step (ia) is in the range of from 45 C. to 15 C.

8. The process according to claim 2, wherein the reaction temperature of step (ia) is in the range of from 30 C. to 15 C.

Description

EXAMPLE

(1) In a 500 ml four neck reaction flask with thermometer, Teflon blade stirrer and a 25 ml funnel for solids is provided under nitrogen: 25.24 g of 6-methyl-5-hepten-2-one (200 mmol), 28.22 g of methyl chloroacetate (260 mmol) and 20 ml of toluene. 14.05 g of sodium methylate (260 mmol) is added to the solution in 1 hour at 20 C. and under stirring with 200 rpm (rotations per minute).

(2) The viscous mixture is stirred for 30 minutes at 0 C., followed by addition of 142.5 ml of sodium hydroxide (2 mol/l; 285 mmol). The biphasic mixture is stirred at 300 rpm for 30 minutes at 40 C. (the viscous phase dissolves in about 5 minutes), followed by addition of 50 ml of toluene. The pH is adjusted at 18 C. to pH=2.0 (pH electrode) by adding about 150 ml of sulfuric acid (1 mol/l; 150 mmol).

(3) The glycidic acid is extracted in 2 funnels with 230 ml of toluene.

(4) The organic phases are washed in series with 220 ml of 5% sodium chloride solution. The organic phases are combined and partially evaporated at the rotavapor (45 C., 50 mbar), police-filtered and concentrated to 70 g at 45 C., 50 mbar to obtain 70 g of glycidic acid (about 44% in toluene).

(5) The solution of the product obtained from (step (i)) is dropped in 90 minutes into a hot reaction flask at 185-190 C. (bath=215 C.) at a vacuum of 100 mbar, and flushed with 5 ml of toluene in 10 minutes.

(6) The compound of formula (I) is obtained in a yield of 58%.