Addition of alcohols and phenols to O-allyl compounds (allyl ethers and acrolein acetals), catalyzed by [RuCl2 (PPh3) 3], was examined. Intramolecular addition of an OH group, leading to the formation of cyclic acetals and orthoesters, was also investigated. As a result, a new, selective and convenient method for the synthesis of symmetrical and unsymmetrical (mixed) acetals and orthoesters was developed.