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 sigma-allyl- and pi-allylruthenium intermediates and ortho-ruthenation of the 2-pyridylarenes via the sigma-allylruthenium intermediate directed by coordination of the 2-pyridyl group to the ruthenium center.