abstract |
The present invention relates to a process for the preparation of compounds or a mixture of compounds of the general formulae I.a or I.b n nwhereinn R 1 is selected from C 1 -C 12 -alkyl, C 3 -C 6 -cycloalkyl, —C(═O)OR 2 , —PO(OR 2a ) 2 , aryl and hetaryl, R 2 , R 2a are independently of each other selected from the group consisting of hydrogen, C 1 -C 12 -alkyl, C 1 -C 12 -alkenyl, where the last two radicals mentioned are unsubstituted, partly or completely halogenated or substituted by 1, 2, 3 or 4 radicals selected from the group consisting of C 1 -C 6 -alkoxy and CN, C 3 -C 6 -cycloalkyl, C 3 -C 6 -cycloalkyl-C 1 -C 4 -alkyl, aryl and aryl-C 1 -C 4 -alkyl, where the last four radicals mentioned are unsubstituted or substituted by 1, 2, 3 or 4 radicals selected from the group consisting of C 1 -C 6 -alkyl, C 1 -C 6 -haloalkyl, C 1 -C 6 -alkoxy, C 1 -C 6 -haloalkoxy, —CN, and halogen, which comprises dimerizing olefin compound of the general formula II, nn n n n n n n n n n in the presence of at least one N-heterocyclic carbene catalyst. |