Process for the production of 2-methyl-4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2-butenal

Abstract

The present invention relates to an improved way to produce 2-methyl-4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2-butenal and derivatives thereof.

Claims

1. A process for the production of a compound of formula (I): ##STR00009## the process comprising the steps of: (i) forming a compound of formula (V): ##STR00010##  wherein R.sub.1 is H or CH.sub.3, by the steps comprising: (ia) forming a Darzens reaction product between (1) a compound of formula (II): ##STR00011##  wherein R.sub.1 is as defined previously, and (2) a compound of formula (III): ##STR00012##  wherein X is Cl or Br, preferably wherein X is Cl, and R.sub.2 is C.sub.1-C.sub.4-alkyl, wherein by carrying out the Darzens reaction between the compounds of formulas (II) and (III) at a reaction temperature in a range from −5° C. to 5° C. in the presence of MOR, wherein R is a C.sub.1-C.sub.4-alkyl group and M signifies Na.sup.+, K.sup.+ or Cs.sup.+, and with from 1.0 to 1.1 mol equivalents of the compound of formula (III), based on the amount of the compound of formula (II), and from 1.0 to 1.1 mol equivalents of MOR, based on the amount of the compound of formula (II), and thereafter (ib) conducting a saponification reaction of the Darzens reaction product of step (ia) at room temperature (25° C.) in the presence of NaOH to form the compound of formula (V), and then subsequently without heating, (ii) subjecting the compound of formula (V) to a decarboxylation reaction at room temperature (25° C.) to obtain the compound of formula (I).

2. The process according to claim 1, wherein step (i) is carried out in at least one solvent.

3. The process according to claim 2, wherein step (i) is carried out in at least one aliphatic alcohol, in at least one aliphatic hydrocarbon, and/or in at least one aromatic hydrocarbon.

4. The process according to claim 3, wherein step (i) is carried out in at least one solvent selected from the group consisting of aliphatic C.sub.1-C.sub.6 alcohols and aliphatic C.sub.5-C.sub.10-hydrocarbons.

5. The process according to claim 1, wherein step (ii) is carried out under normal pressure.

6. The process according to claim 1, wherein R is methyl or ethyl.

7. The process according to claim 1, wherein the Darzens reaction product is a compound of formula (IV): ##STR00013## wherein R1 and R2 are as defined previously.

8. The process according to claim 7, wherein the step (ia) is practiced without isolating the compound of formula (IV).

9. The process according to claim 8, wherein step (ii) is practiced without heating the compound of formula (V).

10. The process according to claim 1, wherein the compound of formula (III) is chloroacetic acid methyl ester and MOR is sodium methylate.

Description

EXAMPLES

Example 1

(1) β-Ionone (17.6 ml, 84 mmol), chloroacetic acid methyl ester (8.2 ml, 93 mmol), methanol (1.9 ml) and n-hexane (1.9 ml) were added to a flask. The solution was cooled to 0° C. Sodium methylate (5.00 g, 93 mmol) was slowly added. The reaction mixture was warmed to room temperature and stirred for 30 min. Aqueous sodium hydroxide (10 ml) in methanol (90 ml) was added over 30 min. Water (150 ml) was added. The reaction mixture was stirred for 10 min. n-Hexane (40 ml) was added and the layers were separated. The aqueous layer was extracted with n-hexane (2×50 ml). The combined organic layers were washed twice with acetic acid (2×16 ml). The organic layer was dried over Na.sub.2SO.sub.4, filtered, and concentrated in vacuo. 2-Methyl-4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2-butenal was obtained (21.0 g, 82% yield, quantitative conversion).