Transition metal complexes as catalysts of double-bond migration in O-allyl systems

This review provides a literature survey of the double-bond migration in O-allyl systems catalyzed by transition metal complexes: allyl aryl, allyl alkyl ethers, cyclic ethers, such as 2,5-dihydrofurane and cyclic acetals, e.g. 4,7-dihydro-1,3-dioxepine derivatives and allyl silyl ethers. The most frequently used catalysts are ruthenium and rhodium phosphine complexes, but other compounds, such as palladium halides, cobalt and iron carbonyls, are also presented. Also, isomerization of allyl carboxylates is mentioned. Recently double-bond migration reactions have been coupled with ring closing metathesis in a tandem reaction in both (one-pot or two-step) ways, and this is also reviewed. The specific aspects of double-bond migration mechanisms in O-allyl systems are presented. Stereoselectivity (E/Z products), as a key parameter of double-bond migration, resulting from steric factors or the possibility of chelating coordination of isomerized molecule, is discussed in the article. The advantages of transition metal complexes applied for double-bond migration catalysis are presented. (c) 2006 Elsevier B.V. All rights reserved.