Anja Frisch

First Kumada reaction of alkyl chlorides using N-heterocyclic carbene/palladium catalyst systems

For the first time it is shown that N-heterocyclic carbenes are suitable ligands for the palladium-catalyzed coupling of alkyl chlorides with aryl Grignard reagents. A variety of simple as well as functionalized primary alkyl chlorides provide the corresponding alkyl benzenes in general in good to very good yield. By comparing the 1,3-dimesitylimidazol-2-ylidene (IMes) palladium(0) naphthoquinone complex with the previously known palladium phosphine catalyst for the model coupling reaction of 1-chlorohexane with phenylmagnesium bromide it is demonstrated that the new catalyst system is superior.

Efficient telomerization of 1,3-butadiene with alcohols in the presence of in situ generated palladium(0)carbene complexes

The palladium-catalyzed telomerization of 1,3-butadiene with alcohols has been studied in presence of palladium and imidazolium salts, which form in situ carbene ligands. Among the different imidazolium salts tested 1,3-dimesitylimidazolium chloride (7), 1,3-bis(ferrocenylmethyl)benzimidazolium tetraphenylborate (12) and 1,3-bis(2-ferrocenylethyl)benzimidazolium bromide (13) gave the best yields of the desired octadienyl ethers. Significantly improved regioselectivities for the linear octadienylethers are obtained in the reaction of 1,3-butadiene and methanol compared to the previously optimized palladium/triphenylphosphine catalyst. Using n-butanol and iso-propanol the palladium carbene catalysts lead to a considerable increase in the corresponding telomerization products compared to standard palladium/triphenylphosphine catalysts.