Process for the preparation of alcohols from alfa, beta-unsaturated aldehydes and ketones

Abstract

A chemoselective process for producing alcohols from ,-unsaturated aldehydes and ketones is described.

Claims

1. A process comprising the steps of: (a) heating to about 30-70 C. a compound of formula (II) ##STR00005## in the presence of hydrogen gas, a base and a homogeneous ruthenium catalyst and thereby forming a compound of formula (III) ##STR00006## (b) followed by increasing the temperature up to about 100-150 C., and thereby forming a compound of formula (I) ##STR00007## wherein in each of formula (I), (II) and (III): R.sup.1 is hydrogen or methyl; R.sup.2 is hydrogen or methyl; R.sup.3 is methyl, or ethyl; R.sup.4 is hydrogen or methyl; and R is a linear or branched C.sub.3-C.sub.10 alkyl comprising at least one non-terminal carbon-to-carbon double bond.

2. The process according to claim 1 wherein the base is an alkali metal compound.

3. The process according to claim 1 wherein the temperature is increased after at least 88% of the compound of formula (II) has been converted to the respective alcohol of formula (III).

4. The process according to claim 1, wherein the catalyst is a homogeneous ruthenium (II) catalyst.

5. The process according to claim 4 wherein the homogeneous ruthenium (II) catalyst is a Ru complex comprising two triarylphosphines, a diamine and two electronegative ligands.

6. The process according to claim 1, wherein the ruthenium catalyst is RuCl.sub.2(PPh.sub.3).sub.2(ethylene-diamine) or RuCl.sub.2(P(para-methyl phenyl).sub.3).sub.2(ethylene-diamine).

7. A process according to claim 1 wherein the ,-unsaturated double bond of the compound of formula (II) is in E-configuration.

8. A process according to claim 1 wherein: R.sup.1 is hydrogen; R.sup.2 is hydrogen; R.sup.3 is methyl; R.sup.4 is methyl; and R is selected from the group consisting of 3-methyl but-2-enyl, 3,7-dimethylocta-2,6-dieneyl, 2,3-dimethylbut-2-enyl, but-2-enyl, 2,4,7-trimethylocta-2,6-dieneyl, and 2-methylpent-2-enyl.

9. A process according to claim 8 wherein R is 3-methyl but-2-enyl.

Description

EXAMPLE 1

(1) Under air atmosphere NaOMe (30 wt % in MeOH) (19.8 g, 4.0 wt %, 0.11 mol) was added to a 1 L stainless steel autoclave containing RuCl.sub.2(PPh.sub.3).sub.2(ethylenediamine) catalyst (0.197 g, 0.26 mmol), 2,4,7-trimethylocta-2,6-dienal (94.2% purity, E/Z, 50:1) (499.2 g, 3.00 mol) and i-PrOH (10 g). While stirring with an overhead stirrer the autoclave was flushed three times with N.sub.2, then three times with H.sub.2, then put under H.sub.2 pressure (41.0 bar) and heated to 50 C. After 3.9 hours almost full CO conversion was observed (>95.5%) by GC (relative peak area) resulting in 2,4,7-trimethylocta-2,6-dienol (compound of formula (III)). The temperature of the autoclave was raised to 120 C. (temperature reached within 0.2 h). After a further 3.9 h the reaction was stopped, cooled to room temperature, the pressure released and the autoclave was flushed three times with N.sub.2. The yellow homogeneous mixture was washed with water (210 mL). The aqueous phase was extracted with methyl tertbutyl ether (350 mL). The organic layer was washed with brine (100 mL), water (100 mL) and dried over MgSO.sub.4 (50.0 g), filtered and concentrated in vacuo. To the obtained yellow liquid paraffin oil (12.3 g) was added and after distillation using a Vigreux column, a colorless liquid of 2,4,7-trimethyloct-6-en-1-ol was obtained (426.2 g, 92.4% purity, 81.9 mol % chemical yield, boiling point=75 C. at 0.5 mbar). In addition to the main product, traces of the intermediate 2,4,7-trimethylocta-2,6-dienol, and double bond isomers thereof have been identified at low concentrations, such as (E)/(Z)-2,4,7-trimethyloct-3,6-dien-1-ol, and (E)/(Z)-2,4,7-trimethylocta-4,6-dienal.

EXAMPLE 2

(2) A 10 mL glass vial was charged with 1 g of 2,4,6-trimethylnona-2,6-dienal (99% purity, E/Z, 32:1), 1 mL cyclohexane, 2.1 mg of Cl.sub.2Ru(PPh.sub.3).sub.2(ethylenediamine) and 210 L of NaOMe (30 wt % in MeOH). The vial was equipped with a stirring bar and sealed. The vial was flushed with N.sub.2 (1 bar) and then three times with H.sub.2 (1 bar) before setting the pressure of H.sub.2 (40 bar). The reaction mixture was heated at 50 C. for 2 h and then 120 C. for a further 2 h. Once cooled, the H.sub.2 overpressure was purged and the vial flushed with N.sub.2. The reaction mixture was quenched with H.sub.2O, the layers separated and the aqueous phase extracted twice with MTBE. The combined organic phases were washed with brine, dried over MgSO.sub.4, filtered and solvent removal provided crude alcohol which was purified by distillation using Kugelrohr (T=100 C., t=15 min, p=0.2 mbar) to provide a colorless liquid of 2,4,6-trimethylnon-6-en-1-ol (450 mg, 82% purity, 36.9 mol % chemical yield).

COMPARISON EXAMPLE 1

(3) Under air atmosphere NaOMe (30 wt % in MeOH) (19.8 g, 4.0 wt %, 0.11 mol) is added to a 1 L stainless steel autoclave containing RuCl.sub.2(PPh.sub.3).sub.2(ethylenediamine) catalyst (0.197 g, 0.26 mmol), 2,4,7-trimethylocta-2,6,dienal (94.2% purity, E/Z, 50:1) (499.35 g, 2.78 mol) and i-PrOH (10 g). While stirring with an overhead stirrer the autoclave is flushed three times with N.sub.2, then three times with H.sub.2, then put under H.sub.2 pressure (41.0 bar) and heated to 120 C. After 22 hours almost full CO conversion is observed (>95.5%) measured by GC (relative peak area). The reaction is stopped, cooled to room temperature, the pressure released and the autoclave is flushed three times with N.sub.2. The yellow homogeneous mixture is washed with water (210 mL). The aqueous phase is extracted with methyl tertbutyl ether (350 mL). The organic layer is washed with brine (100 mL), water (100 mL) and dried over MgSO.sub.4 (50.0 g), filtered and concentrated in vacuo. To the obtained yellow liquid is added paraffin oil (12.3 g) and after distillation using a Vigreux column, a colorless liquid of 2,4,7-trimethyloct-6-en-1-ol is obtained (298.5 g, 89.1% purity, 69 mol % chemical yield).