Ortho-selective allylation of 2-pyridylarenes with allyl acetates catalyzed by ruthenium complexes

The ortho-position of 2-pyridylarenes is selectively allylated with allyl acetates in the presence of a ruthenium(II)-phosphine complex. In the case of aromatic-substituted allyl acetates, such as cinnamyl acetate, linear allylated compounds were the predominant products. However, the reaction with linear aliphatic allyl acetates afforded a mixture of linear and branched products, whereas reactions with branched aliphatic allyl acetates afforded linear products preferentially. From these results, the reaction mechanism is proposed to involve the formation of σ-allyl- and π-allylruthenium intermediates and ortho-ruthenation of the 2-pyridylarenes via the σ-allylruthenium intermediate directed by coordination of the 2-pyridyl group to the ruthenium center.