PROCESS FOR THE PREPARATION OF INTERMEDIATES FOR THE SYNTHESIS OF VITAMIN A DERIVATIVES FROM POLYENES BY CYCLISATION

Abstract

The application relates to a process for the preparation of a compound of formula (II) by cyclisation of a polyene of formula (I), and to an intermediate of formula (III). The obtained compounds are useful intermediates in the preparation of specific isoprenoids, preferably in the production of vitamin A and derivatives of vitamin A.

##STR00001##

Claims

1. Process for the production of a compound of formula (II) ##STR00010## by cyclisation of a compound of formula (I) ##STR00011## in the presence of at least one strong Brønsted acid.

2. Process according to claim 1, wherein the acid is a solid acid.

3. Process according to claim 1 or 2, claim 1, wherein the acid is an ion-exchange resin, which has sulfonic acid groups.

4. Process according to claim 1, wherein the acid is a liquid acid.

5. Process according to claim 1, wherein the acid is a compound of the following formula (VI)
R—SO.sub.3H  (VI), wherein R is C.sub.1-C.sub.4-alkyl, Cl, CH.sub.3 or CF.sub.3.

6. Process according to claim 1, wherein the acid is chosen from the group consisting of CH.sub.3SO.sub.3H, ClSO.sub.3H and CF.sub.3SO.sub.3H.

7. Process according to claim 1, wherein the acid is used in an amount of 0.5 mol-equivalent (in view of the compound of formula (I)) up to 10 mol-equivalent (in view of the compound of formula (I)).

8. Process according to claim 1, wherein the process is carried out in the presence of at least one inert solvent.

9. Process according to claim 1, wherein the process is carried out in at least one polar aprotic solvent.

10. Process according to claim 1, wherein the process is carried out at a temperature of from −50° C. to 50° C.

11. Process according to claim 1, wherein the process is carried out at a residence time (□) of 5-30 minutes.

12. Process according to claim 1, wherein the process is carried out batch-wise.

13. Process according to claim 1, wherein the process is carried out continuously.

14. A compound of formula (III) ##STR00012##

Description

EXAMPLES

Example

Example 1

[0049] 17.7 g (0.18 mol) of methane sulfonic acid is mixed with Dichloromethane (40 ml) and cooled to −38° C.

[0050] 8.8 g (0.034 mol) of compound of formula (I) is added under stirring in a period of 10 minutes.

[0051] The mixture is stirring another 15 min at −30 to −39° C.

[0052] The reaction mixture is quenched in 80 ml water and extracted with 80 ml t-BME. Layers were separated.

[0053] The water layer is extracted with 2×40 ml t-BME and the organic layer is washed with 40 ml water.

[0054] The organic layer neutralized with 5 ml Et.sub.3N (pH: 9) and then washed with 50 ml water.

[0055] After separation of the layers, the organic phase is dried on Na.sub.2SO.sub.4 and concentrated on a rotavapor.

[0056] The overall yield of the compound of formula (II) was 44%.