Method for producing specific α,β-unsaturated aldehydes by rearrangement process

Abstract

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

Claims

1. A process for producing a compound of formula (I): ##STR00012## wherein R.sup.1 is a C.sub.1-C.sub.4-alkyl moiety, and R.sup.2 is ##STR00013## wherein the process comprises rearranging a compound of formula (II): ##STR00014## wherein R.sup.1 and R.sup.2 have the same meanings as in formula (I), in the presence of at least one Cu and/or Ti transition metal based catalyst.

2. The process according to claim 1, wherein the compound of formula (II) is a compound of formula (IIa): ##STR00015##

3. The process according to claim 1, wherein the compound of formula (II) is a compound of formula (IIb): ##STR00016##

4. The process according to claim 1, wherein the transition metal-based catalyst is a Cu/Ti-based catalyst.

5. The process according to claim 1, wherein the transition metal-based catalyst is CuCl/Ti(O)(acac).sub.2.

6. The process according to claim 1, wherein the transition metal-based catalyst has a mol-based substrate to catalyst ratio from 5000:1 to 10:1.

7. The process according to claim 1, wherein the process is carried out in at least one nonpolar or polar aprotic organic solvent.

8. The process according to claim 1, wherein the process is carried out at a reaction temperature of 50 C. to 120 C.

9. The process according to claim 8, wherein the reaction temperature is 60 C. to 100 C.

10. The process according to claim 1, wherein R.sup.1 is CH.sub.3 or CH.sub.2CH.sub.3.

11. The process according to claim 6, wherein the mol-based substrate to catalyst ratio is from 1000:1 to 20:1.

Description

EXAMPLES

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

(1) 8.74 mg of titanium(IV)-oxyacetylacetonate (0.03 mmol) and 4.08 mg of copper(I)-chloride (0.04 mmol) were added to a vial. The vial was sealed with a septum. 0.46 g of starting material (IIb, 2.00 mmol) in 4 ml of anhydrous toluene was added. The solution was stirred for 15 hours at 90 C., then cooled to 23 C. and stirred for another 3.5 hours. The solution was diluted with 15 ml of ethyl acetate and washed with 15 ml of diluted brine (20%). The layers were separated and the organic layer was washed with another 15 ml of diluted brine (20%). The aqueous layers were re-extracted with 15 ml of ethyl acetate. The combined organic layers were dried over sodium sulfate, filtered and concentrated under reduced pressure at 30 C. water-bath temperature. The product (Ib) was obtained as a dark brown oil in 26.12% purity and 27% yield (0.455 g).

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

(2) 8.7 mg of titanium(IV)-oxyacetonylacetonate and 4.1 mg of copper(I)-chloride were added to a flask. A solution of 651.7 mg of starting material (IIa) in 4.0 ml of anhydrous toluene were added drop wise. The reaction mixture was heated to 85 C. in an oil bath under argon atmosphere. After 48 hours at 85 C. the dark brown suspension was cooled to 24 C. 15 ml of methylene chloride were added to the reaction mixture. The mixture was washed with 15 ml of semi-saturated NaHCO.sub.3-solution and 15 ml of semi-saturated brine. The layers were separated and the aqueous layers were re-extracted with 15 ml of methylene chloride. The combined organic layers were dried over sodium sulfate, filtered and concentrated under reduced pressure at 30 C. water bath temperature. The product (Ia) was obtained as dark orange oil (707.1 mg).