Process for the preparation of aromatic aldehydes

1. A process for the preparation of (hetero)aromatic aldehydes comprising:

reacting a halogen-substituted (hetero)aromatic compound, with CO and H 2 in the presence of a base and a palladium catalyst having a monodentate phosphane ligand of the general formula (I)

wherein

R 1 and R 2 independently of one another are (C 5 -C 20 )-alkyl, where the C atom which is bonded to phosphorus is a tertiary centre, and

R 3 is a primary, optionally linear (C 3 -C 20 )-alkyl radical.

2. The process according to claim 1 , wherein the base is an inorganic or organic base.

3. The process according to claim 1 , wherein

the reacting optionally comprises a solvent selected from the group consisting of NMP (N-methylpyrrolidone), DMGE (dimethyl glycol ether), hexane, heptane, octane, toluene, xylene, anisole, DMF (dimethylformamide), DMAC (dimethylacetamide), 1,4-dioxane, MTBE, THF, acetonitrile, benzonitrile, ethyl acetate, isopropyl acetate, dibutyl ether, dimethyl carbonate, diethyl carbonate, and dipropyl carbonate.

4. The process according to claim 1 , wherein a CO pressure is from 0.05 to 10 MPa.

5. The process according to claim 1 , wherein a molar ratio of CO to H 2 is in the range from 5:1 to 1:5.

6. The process according to claim 1 , wherein a mol % of catalyst based on moles of (hetero)aromatic is from 0.001 mol % to 10 mol %.

7. The process according to claim 1 , wherein a palladium:phosphane molar ratio is from 1:0.1 to 1:20.

8. The process according to claim 1 , wherein a temperature of the reacting is in the range from 70 to 170° C.

9. The process according to claim 1 , wherein R 1 and R 2 are polycyclic radicals.

10. The process according to claim 9 , wherein R 1 and R 2 are each an adamantyl radical.

11. The process according to claim 10 , wherein R 3 is a n-alkyl radical selected from the group consisting of n-butyl, n-pentyl and n-hexyl.

12. The process according to claim 11 , wherein R 3 is n-butyl.