Process for alkoxycarbonylation of ethylenically unsaturated compounds using benzene-based diphosphine ligands and aluminium triflate

1. Process comprising the process steps of:

a) initially charging an ethylenically unsaturated compound,

b) adding a ligand of formula (I):

where

R 1 and R 3 are each a —(C 3 -C 20 )-heteroaryl radical,

R 2 and R 4 are each —(C 1 -C 12 )-alkyl,

and a compound comprising Pd;

c) pretreating aluminium triflate at least twice by applying a vacuum to reduce pressure and the vacuum applied is broken by flooding with inert gas;

d) adding the pretreated aluminium triflate from c) as a solution, where the ratio of aluminium triflate:ligand is in the range from 2.5 mol:1 mol to 15 mol:1 mol;

e) adding an alcohol;

f) feeding in CO;

g) heating the reaction mixture from a) to f), with conversion of the ethylenically unsaturated compound to an ester.

2. Process according to claim 1 ,

where R 1 , R 3 are each selected from furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, pyrazolyl, furazanyl, tetrazolyl, pyridyl, pyridazinyl, pyrimidyl, pyrazinyl, benzofuranyl, indolyl, isoindolyl, benzimidazolyl, quinolyl, isoquinolyl.

3. Process according to claim 1 ,

where R 2 and R 4 are ter Bu.

4. Process according to claim 1 ,

wherein the ligand in process step b) has the formula (1):

5. Process according to claim 1 ,

wherein the process comprises the additional process step c′):

c′) dissolving the pretreated aluminium triflate from c) in a solvent.

6. Process according to claim 5 ,

wherein the solvent used in process step c′) is the same alcohol as in process step e).

7. Process according to claim 1 ,

wherein the compound in process step b) comprising Pd 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.

8. Process according to claim 1 ,

wherein the alcohol in process step e) is selected from methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tart-butanol, 3-pentanol, cyclohexane, phenol, or mixtures thereof.

9. Process according to claim 1 ,

wherein the alcohol in process step e) is methanol.