Patent ID: 8003838

Claim:
A process for the catalytic reduction by 1,4-hydrogenation, using molecular H 2 , of a C 5 -C 22 conjugated diene of formula wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 represent, simultaneously or independently from each other, a hydrogen atom or a C 1 -C 12 alkyl or alkenyl group optionally substituted; one of R 2 or R 6 may also represent a C 1 -C 12 alkoxy or acyloxy group optionally substituted; and R 1 and R 3 , or R 3 and R 4 , or R 2 and R 6 , or R 6 and R 5 , or R 4 and R 5 , taken together, may form a C 2-16 alkanediyl or de-conjugated alkenediyl group, optionally substituted; into the corresponding alkene, of formula wherein R 1 to R 6 have the same meaning as for the compound of formula (I), and wherein the isomer having the R 1 and R 2 groups in a cis configuration is predominant; wherein said process is carried out in the presence of at least one ruthenium catalyst or pre-catalyst of formula [Ru(L)(Diene)(L′) n ]X (III) wherein L represents a C5-C25 substituted cyclopentadienyl ligand, Diene represents a C4-C22 diene and X represents a non coordinated anion, n represents 2, 1 or 0 and L′ represents a solvent; and at least an acidic additive selected from the group consisting of: a compound of formula R 14 (3-x) MO(OH) x , wherein R 14 is a R 14′ or R 14′ O group wherein R 14′ is a C 1 -C 10 group, M is P or As and x is 1 or 2; and a boron derivative of formula R 14 B(OH) 2 , wherein R 14 is as defined above; and phenol or a phenol substituted by up to three C 1 -C 4 alkyl, alkoxy or carboxylic groups, nitro groups or halogen atoms; and a C 1 -C 12 mono-carboxylic non-amino acid; and a HOOCCH═CHCOOH di-acid, and the tetronic acid; provided that the processes wherein compound (I) is sorbol and compound (III) is of formula [Ru(Cp*)(COD)]X are excluded.