The Chemistry of Azaindoles [Pyrrolo[2,3]pyridines

Abstract

The review discusses the chemical properties and the biological activity of aza-analogues of indole compounds, i.e. substancescontaining fused pyridine and pyrrole systems. The interest taken in azaindole derivatives is due on the one hand to the ever broadening application during recent years of theprinciple of building up aza-analogues of biologically active substances (purines, pyrimidines, steroids, etc.) as bases in the searchfor new medicinal preparations, and on the other hand to the appearance in such systems of characteristic chemical properties,indicating a redistribution of electron density caused by the interaction of the "π-electron-deficient" and "π-electron-excessive"rings involved in the fusion. The above problems are fully reflected in the review. Considerable attention is paid to discussing the chemical peculiarities ofazaindoles associated with the presence in the fused systems of rings which have directly opposite displacements of π-electronsrelative to carbon atoms, describing the features of lactam–lactim and amino–imino tautomerism in azaindole and azaindolinesystems, and also examining routes and methods for introducing substituents both into the pyridine and into the pyrrole partsof the molecule. Exhaustive consideration is given to data on the biological activity of azaindoles. A special section is concernedwith the choice of methods for building up azaindole systems and the characteristics of ring-closure in azaindoles comparedwith indoles. The review covers all information available in the world's literature on the chemistry and the biological activity of azaindoles.The list of references comprises 159 items.