Patent ID: 6844463

Claim:
A process for the carbonylation of n-pentenoic acid or its derivatives of the formula (I) C 4 H 7 —R 1 (I) where R 1 is —CN or COOR 2 where R 2 is hydrogen, alkyl or aryl by reaction of a compound of the formula (I) with carbon monoxide and a compound (II) containing a hydroxyl group in the presence of a catalyst system, wherein the catalyst system is obtained by reaction of a) a source for a metal ion of a metal (III) of the 8th subgroup of the Periodic Table of the Elements with b) a bidentate phosphine ligand of the formula (IV) (R 3 R 4 R 5 C)(R 6 R 7 R 8 C)P-L 1 -X-L 2 -P(CR 9 R 10 R 11 ) (CR 12 R 13 R 14 ) (IV) where R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 independently of one another is an organic radical which in each case contains a carbon atom, via which the respective radical is linked to the relevant tertiary carbon atom shown in formula (IV); L 1 , L 2 independently of one another are a lower alkylene group; X is an arylene group.