Abstract: .beta., .gamma.-Unsaturated carboxylic acids, e.g., 3-hexene-1,6-dioic acid, are selectively prepared by carbonylating (with carbon monoxide) an allyl alcohol, e.g., a butenediol, at an elevated temperature and under superatmospheric pressure, in the presence of a catalytically effective amount of a palladium-based catalyst and at least one quaternary onium chloride of one of the Group VB elements nitrogen or phosphorus, such element being tetracoordinated via carbon atoms and with the proviso that such nitrogen atom may be coordinated to two pentavalent phosphorus atoms.

Abstract: The hexene-1,6-dioic acids, e.g., hex-3-ene-1,6-dioic acid, are prepared by reacting carbon monoxide and water with at least one diacyloxylated butene, in the presence of a catalytically effective amount of palladium and at least one quaternary onium chloride of one of the Group VB elements nitrogen or phosphorus, such element being tetracoordinated via carbon atoms and with the proviso that such nitrogen atom may be coordinated to two pentavalent phosphorus atoms.

Abstract: Hexene-1,6-dioates, readily hydrogenated into adipates (which in turn are conveniently hydrolyzed into adipic acid), are prepared by reacting carbon monoxide, an alcohol and at least one dichlorobutene, in the presence of a catalytically effective amount of palladium or a palladium compound and no more than two equivalents (relative to the dichlorobutene) of a tertiary amine reaction promoter; in an alternate embodiment, the tertiary amine and the dichlorobutene are first converted into a quaternary ammonium chloride intermediate.

Abstract: The process according to the invention consists in dimerizing a conjugated diene in the presence of a catalyst obtained by bringing together (A) at least one nickel complex of formula NiZ.sub.q in which q is the coordination number of the nickel and Z is at least one ligand capable of complexing nickel and (B) at least one phosphorus-containing ligand of general formula ##STR1## in which: R.sub.1 is chosen from a hydrogen atom and hydrocarbon radicals,R.sub.2 and R.sub.3, which may be identical or different, are chosen from a hydrogen atom and hydrocarbon radicals optionally bearing at least one group chosen from alcohol, thiol, thioether, amine, imine, acid, ester, amide and ether groups, andm is greater than or equal to 1.