Double bond migration in N-allylic systems catalyzed by transition metal complexes

Abstract

In this review, literature reports on isomerization of N-allyl: amines, imines, amides, imides, carbamates and nitrogen-heterocycles to their corresponding N-(1-propenyl) compounds, catalyzed by transition metal complexes are discussed. To the best of our knowledge, all applications of isomerization of N-allyl compounds, mediated by Rh, Ru, Fe, Ir, Cr, Ti, Co and Os complexes for highly ( E-, Z-, or enantio-) selective syntheses of enamines, enamides, azadienes and other compounds described in the literature are reviewed. All papers dealing with asymmetric isomerization of the prochiral N-allyl systems, particularly N-allylamines, are analyzed. Also tandem reactions: isomerization-RCM and RCM-isomerization, as well as cascades of reactions leading to heterocyclic systems containing N and O or S atoms in the ring are described. Moreover, procedures for deallylation of N-allyl compounds ( via isomerization), in which the intermediates, i.e. N-(1-propenyl) systems, were or may be separated, are reviewed. The first stage of such procedures (the isomerization) is therefore also a method for synthesis of N-(1-propenyl) compounds. Relationships between structure and reactivity are analyzed too, particularly the influence of nitrogen atom coordination on the outcome of the reaction between an N-allyl system and a transition metal complex. It is clear, as demonstrated by many authors, that participation of the nitrogen atom in coordination of the metal atom determines the stereochemistry of double bond migration. However, too strong a coordination of N-allyl by the metal atom precludes double bond migration and favors a cleavage of allyl C N bond. Such stoichiometric transformations are also analyzed in this paper. Furthermore, our literature survey shows that dependencies between donor–acceptor properties of N-allyl compounds and their reactivity are particularly well documented for ruthenium complexes. However, the influence of the type of the central atom on the outcome of reaction of N-allyl compounds with a transition metal complex is poorly understood.