NOVEL ENOL-ACETATES(II)

Abstract

The present invention relates to new specific enol esters of formula (I) as well as to a process for their production by acylation of the corresponding dihydroretinal analogue. In formula (I) R is —COR′ where R′ is a C.sub.1-C.sub.16 alkyl group.

##STR00001##

Claims

1. Compounds of formula (I) ##STR00015## wherein R is —COR′, wherein R′ is a C.sub.1-C.sub.16 alkyl group (especially C.sub.1, C.sub.2 and C.sub.15).

2. Compounds according to claim 1, which has formula (Ia) ##STR00016## wherein R is —COR′, wherein R′ is a C.sub.1-C.sub.16 alkyl group (preferably a C.sub.1, C.sub.2 or C.sub.15-alkyl group)

3. Compound according to claim 1, which has formula (Ib) ##STR00017## wherein R is —COR′, wherein R′ is a C.sub.1-C.sub.16 alkyl group (preferably a C.sub.1, C.sub.2 or C.sub.15-alkyl group).

4. Process for the production of the compounds of formula (I) according to claim 1 ##STR00018## wherein R is —COR′, wherein R′ is C.sub.1-C.sub.16 alkyl group (preferably a C.sub.1, C.sub.2 or C.sub.15-alkyl group) by acetylation of a compound of formula (II) ##STR00019## by using at least one acetylating agent of formula (III) ##STR00020## wherein ##STR00021## R is —COR′ or wherein R′ is a C.sub.1-C.sub.16 alkyl group (preferably a C.sub.1, C.sub.2 or C.sub.15-alkyl group) and R″ is a C.sub.1-C.sub.16 alkyl group (preferably a C.sub.1, C.sub.2 or C.sub.15-alkyl group).

5. Process according to claim 4, wherein the process is carried out in the presence of at least one transition metal catalyst.

6. Process according to claim 4, wherein the amount of the catalyst is 0.001 mol-equivalent up to 0.01 mol-equivalent (in relation to compound of formula (II)).

7. Process according to claim 4, wherein the process is carried out in the presence of at least one organic acid.

8. Process according to claim 4, wherein the process is carried out in the presence of at least one base.

9. Process according to claim 7, wherein the amount of the acid or base is 0.005 mol-equivalent up to 0.1 mol-equivalent (in relation to compound of formula (II)).

10. Process according to claim 4, wherein the process is carried out in an inert solvent.

11. Process according to claim 4, wherein the process is carried out without any solvent.

12. Process according to claim 4, wherein the process is carried out at a temperature of from 0° C. 100° C. (preferably from 5° C. 90° C.).

Description

Examples

Example 1:

[0042] A flame-dried 2-necked flask equipped with a reflux condenser was charged with p-toulenesulfonic acid (dry, 0.01 eq), hydroquinone (0.01 eq), copper(I1)acetate (0.004 eq), isopropenylacetate (2.0 eq) and 3,7-dimethyl-9-(2,6,6-trimethylcyclohex-1-en-1-yl)nona-2,4,6-trienal (1.0 eq) in the given order. The reaction mixture was stirred for 3 h at 60 ° C., cooled to room temperature and Et.sub.2O (10 mL) was added. The solution was washed with aqueous sat. NaHCO.sub.3-solution (5 mL). The aqueous phase was extracted with Et2O (5 mL) and the combined organic layers were concentrated under reduced pressure (45° C., 2 mbar). The crude material was filtered over silica (first washed with heptane, then with ethylacetate) to afford the product as mixture of isomers.