Methoxy pyridyl ligand and application thereof in alkoxy carbonylation

Abstract

The invention relates to a methoxy pyridyl ligand and an application of the methoxy pyridyl ligand in alkoxy carbonylation.

Description

[0001] The present invention relates to a methoxypyridyl ligand and its application in alkoxycarbonylation.

[0002] The alkoxycarbonylation of olefinically unsaturated compounds is an increasingly important method. Alkoxycarbonylation is understood to mean the reaction of an olefinically unsaturated compound (olefin) with carbon monoxide and an alcohol in the presence of a metal-ligand complex to obtain the corresponding ester. Generally, the metal used is palladium. The following scheme shows the general reaction equation for alkoxycarbonylation:

[0003]

[0004] The technical object of the present invention is to provide a novel ligand / method that can improve the conversion rate.

[0005] This object is achieved by the compound according to claim 1.

[0006] Compound of formula (I):

[0007]

[0008] wherein one of the two groups R 1 , R 2 is -O-(C 1 -C 4 )-alkyl and the other group is -H.

[0009] In one embodiment, one of the two groups R 1 , R 2 is -O-CH 3 and the other group is -H.

[0010] In one embodiment, the compound has structure (1):

[0011]

[0012] In one embodiment, the compound has structure (2):

[0013]

[0014] In addition to the compound itself, a method of using the compound is also claimed.

[0015] Method, which comprises the following method steps:

[0016] a) Initially loading an olefinically unsaturated compound;

[0017] b) Adding the compound of formula (I) above;

[0018] c) Adding a Pd compound;

[0019] d) Add a cocatalyst selected from: aluminum trifluoromethanesulfonate, H 2 SO 4 , MSA, pTSA, TFA;

[0020] e) Add an alcohol;

[0021] f) Feed in CO;

[0022] g) Heat the reaction mixture from a) to f), wherein the ethylenically unsaturated compound is converted into an ester.

[0023] It is possible to add these substances in any order. However, usually CO is added after the co-reactants have been initially charged in steps a) to e). In addition, CO can also be fed in in multiple steps in the following manner: for example, first feed in a part of CO, then heat, and then feed in another part of CO.

[0024] In a variant of the method, the Pd compound is selected from: palladium dichloride, palladium(II) acetylacetonate, palladium(II) acetate, dichloro(1,5-cyclooctadiene)palladium(II), bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloropalladium(II), (cinnamyl) palladium dichloride.

[0025] In a variant of the method, the Pd compound is selected from: Pd(dba) 2 、Pd(acac) 2 or Pd(OAc) 2 .

[0026] In a variant of the method, the Pd compound is Pd(acac) 2 .

[0027] In a variant of the method, the alcohol in process step e) is selected from: methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, cyclohexanol, phenol or a mixture thereof.

[0028] In a variant of the method, the alcohol in process step e) is methanol.

[0029] In a variant of the method, the alcohol in process step e) is used in excess.

[0030] In a variant of the method, the alcohol in process step e) is simultaneously used as a solvent.

[0031] In a variant of the method, CO is fed in at a CO partial pressure of 1 to 5 MPa (10 to 50 bar) in process step f).

[0032] In a variant of the method, CO is fed in at a CO partial pressure of 1 to 5 MPa (10 to 40 bar) in method step f).

[0033] In a variant of the method, the reaction mixture is heated to a temperature of 40 °C to 140 °C in method step g).

[0034] In a variant of the method, the reaction mixture is heated to a temperature of 80 °C to 140 °C in method step g).

[0035] In a variant of the method, the ethylenically unsaturated compound used is diisobutene.

[0036] In a variant of the method, the ethylenically unsaturated compound used is a mixture of 2,4,4-trimethylpent-1-ene (TMP1) and 2,4,4-trimethylpent-2-ene (TMP2).

[0037] In a variant of the method, the cocatalyst is aluminium trifluoromethanesulfonate.

[0038] The invention is illustrated in more detail below with reference to working examples.

[0039] General procedure

[0040] The operations are carried out under an argon atmosphere. The reaction vessel has been pre-dried under the action of heat (80 °C) and a vacuum from an oil pump. The liquid substances are degassed for at least 15 minutes by bubbling with argon. The acid used is aluminium trifluoromethanesulfonate (Al(OTf) 3 ). The ligands used are (1), (2), and the comparative ligands used are (3), (4). The precursor used is palladium(II) bis(acetylacetonate) (Pd(acac) 2 ). The substrate used is diisobutene, which is a mixture of the two C8 isomers 2,4,4-trimethylpent-1-ene (TMP1) and 2,4,4-trimethylpent-2-ene (TMP2) in a ratio of 79:21.

[0041]

[0042] Conversion of the substrate diisobutene (DiB)

[0043]

[0044] Precursor stock solution:

[0045] Pd(acac) 2 (10 mg, 33 μmol) is weighed into a 20 mL vial, sealed airtight with the aid of a flanged septum, and dissolved in methanol (10 mL).

[0046] The reaction was carried out in a 20 mL glass vessel equipped with a magnetic stir bar. First, Al(OTf) 3 (0.8 mol%) and the ligand (0.2 mol%) were weighed into the glass vessel and then sealed airtight with the help of a flange septum. In a subsequent step, an argon atmosphere was ensured with the help of a puncture cannula connected to an argon distribution station and, at the same time, the possibility of pressure equalization (addition of solution) was present. The required amount of the precursor stock solution (1.5 ml) was added with a μL syringe to obtain the starting weight of Pd(acac) 2 (0.05 mol%). Finally, methanol was added with a μL syringe to bring the total volume to 8.4 mL. The autoclave was sealed, purged three times with nitrogen, and the seal was tested with 20 bar of nitrogen. After establishing the seal, the same procedure was carried out with CO. Then the reaction solution was heated to the required temperature of 120 °C. After 20 minutes at a constant temperature, the substrate was transferred to the reaction vessel with the help of an HPLC pump. After 15 minutes, samples were withdrawn via the substrate line respectively.

[0047] The conversion rates are listed in the table below:

[0048] Ligand Conversion rate (TMP1) [%] Conversion rate (TMP2) [%] (1)* 88 32 (2)* 28 1 (3) 6 0 (4) 9 0

[0049] *Examples of the present invention

[0050] The experiments carried out have proven that the object has been achieved by means of the compounds according to the invention.

Claims

1. A compound of formula (I): The two groups R 1 , R 2 One of them is -O-(C 1 -C 4 )-alkyl, and the other group is -H.

2. The compound according to claim 1, wherein one of the two groups R 1 and R 2 is -O-CH 3 , and the other group is -H.

3. The compound according to any one of claims 1 or 2, wherein the compound has structure (1):

4. The compound according to any one of claims 1 or 2, wherein the compound has structure (2):

5. A method, which comprises the following method steps: a) Initially loading an ethylenically unsaturated compound; b) Adding the compound according to any one of claims 1 to 4; c) Adding a Pd compound; d) Add a cocatalyst selected from: aluminum trifluoromethanesulfonate, H 2 SO 4 , MSA, pTSA, TFA; e) Adding an alcohol; f) Feeding in CO; g) Heating the reaction mixture from a) to f), wherein the ethylenically unsaturated compound is converted into an ester.

6. The method according to claim 5, wherein the Pd compound is selected from: palladium dichloride, palladium(II) acetylacetonate, palladium(II) acetate, dichloro(1,5-cyclooctadiene)palladium(II), bis(dibenzylideneacetone)palladium, bis(acetonitrile)dichloropalladium(II), (cinnamyl)dichloropalladium.

7. The method according to any one of claims 5 or 6, wherein the alcohol in method step e) is selected from: methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, cyclohexanol, phenol or a mixture thereof.

8. The method according to any one of claims 5 to 7, wherein the alcohol in method step e) is methanol.

9. The method according to any one of claims 5 to 8, wherein in method step f) CO is fed in at a CO partial pressure of 1 to 5 MPa (10 to 50 bar).

10. The method according to any one of claims 5 to 9, wherein in method step g) the reaction mixture is heated to a temperature of 40 °C to 140 °C.

11. The method according to any one of claims 5 to 10, wherein the ethylenically unsaturated compound used is diisobutene.

12. The method according to any one of claims 6 to 11, wherein the cocatalyst is aluminum trifluoromethanesulfonate.

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