Synthesis of bis-oxazoline-ruthenium(II)-arene complexes.: Combined catalytic isomerisation and Claisen rearrangement of bis-allyl ether

Bis-oxazolines 1a–c and 2-benzothiazol-2-ylmethyl-benzooxazole (1d) (NN) react with [RuCl2(p-cymene)]2 in polar solvent with NH4BF4 or NH4PF6 and lead to ionic arene-ruthenium complexes [RuCl(NN)(p-cymene)]+X− (3a–d) in quantitative yields. These complexes are easily deprotonated on the bridging methylene group and their electrochemical study shows the subtle influence of the substituents on the electron richness of the ruthenium atom. Complex 3b in the presence of both 1,3-bis(2,6-diisopropylphenyl)imidazolinium chloride 6 and Cs2CO3 (1/1/2) catalyses the selective transformation of bis-allyl ether into γ,δ-unsaturated aldehyde via successive alkene isomerisation and Claisen rearrangement.