METHOD FOR PRODUCING SPECIFIC ALPHA, BETA-UNSATURATED ALDEHYDES

Abstract

The present invention relates to an improved method for producing specific α, β-unsaturated aldehydes.

Claims

1. A process of production of a compound of formula (I) ##STR00016## wherein R.sup.1 is a C.sub.1-C.sub.4-alkyl moiety, preferably —CH.sub.3 or —CH.sub.2CH.sub.3, R.sup.2 is ##STR00017## by rearrangement of the compound of formula (II) ##STR00018## wherein R.sup.1 and R.sup.2 have the same meanings as in formula (I), wherein the process is carried out in the presence of at least one Ruthenium based catalyst.

2. A process according to claim 1, wherein the compound of formula (II) is the compound of formula (IIa) ##STR00019##

3. A process according to claim 1, wherein the compound of formula (II) is the compound of formula (IIb) ##STR00020##

4. A process according to claim 1, wherein the catalyst (C.sup.1) ##STR00021## wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 signify independently from each other —H, —CH.sub.3, —OCH.sub.3, —NO.sub.2 or halogene, and m, n, o and p are independently from each other an integer of 0, 1, 2 or 3, and X and Y are independently from each other an allylic moiety, and q signifies an integer of 1, 2, 3, 4, 5, or 6, and is used.

5. A process according to claim 1, wherein (C.sup.1′) ##STR00022## is used.

6. A process according to claim 1, wherein the substrate to catalyst ratio (mol-based) is from 5000:1 to 10:1, preferably from 1000:1 to 20:1.

7. A process according to claim 1, wherein the process is carried out in at least one non polar or polar aprotic organic solvent in the presence of at least one organic acid having a pK value in the range of about 4.0 to about 6.5.

8. A process according to claim 1, wherein the process is carried out at a reaction temperature of 10° C. to 50° C., preferably 20° C. to 40° C.

Description

EXAMPLES

Example 1: 3-Methyl-5-(2,6,6-trimethylcyclohex-1-enyl)penta-2,4-dienal (Compound of Formula (Ib))

[0049] Ethynol (compound of formula IIb) (212 g, 0.90 mol) and benzoic acid (165.7 g, 1.35 mol, 1.5 eq.) were dissolved in 805 ml of ethyl acetate. The solution was set under argon atmosphere. In a counter flow of argon, 8.26 g (13.5 mmol, 1.5 mol %) of the ruthenium catalyst of formula (C.sup.1′) were added. Upon addition of the catalyst a slightly exothermic reaction was observed as the temperature of the reaction mixture increased from 24° C. to 31° C. After stirring for 23 hours at 24° C., TLC indicated that the reaction was complete. At the same temperature 8.8 ml of 10% sulfuric acid were added drop wise which caused a temperature increase to 35° C. After 23 hours at 24° C. the reaction was complete (TLC) and the dark brown reaction mixture was transferred into a 5-litre separation funnel, diluted with ethyl acetate (1 l) and washed with brine (2×1 l). The aqueous layers were re-extracted with ethyl acetate (1 l). The combined organic layers were dried over sodium sulfate, filtered and concentrated under reduced pressure (rotavap, 40° C. water-bath temperature). The crude product was dried for another 2 hours at 20 mbar resulting in a dark brown oil (233.5 g, ˜75% purity, 88% yield). The product (compound of formula (Ib) was then purified.

Example 2: Retinal (Compound of Formula (Ia))

[0050] C.sub.20-propargyl alcohol (compound of formula IIa) (1.21 g, 4.0 mmol) and benzoic acid (0.736 g, 6.0 mmol, 1.5 eq.) were dissolved in 4.4 ml of ethyl acetate. The resulting yellow solution was set under argon atmosphere. In a counter flow of argon, 24.5 mg of ruthenium catalyst of formula (C.sup.1′) were added (slightly exothermic reaction, temperature increase to 30° C.). After stirring for 18 h at 24° C. TLC indicated that the acid addition was complete and 4 μl of diluted sulfuric acid (10%) were added (slightly exothermic reaction, temperature increase to 30° C.). After stirring for another 3 hours at 24° C., the reaction was complete (TLC). The dark brown reaction mixture was transferred into a 25-ml separation funnel, diluted with 5 ml of ethyl acetate, neutralized with aqueous NaHCO.sub.3-solution (3×5 ml) (careful: gas evolution) and washed with water (2×5 ml) and brine (1×5 ml). The aqueous layers were re-extracted with 5 ml of ethyl acetate. The combined organic layers were dried over sodium sulfate, filtered and concentrated under reduced pressure (rotavap, 40° C. water-bath temperature). The crude product was obtained as dark brown oil in 67% yield (1.36 g, 56.3% purity) and purified.