Cu(II) complex based on 3-hydroxy-2-naphtoic acid (Cu-HNA) as an efficient catalyst for the one-pot multicomponent synthesis of triazolo[1,2-a]indazole-triones under solvent free conditions

Multicomponent reactions (MCRs) are important for the achievement of high levels of diversity, as they allow more than two building blocks to be combined in practical, time-saving one-pot operations, giving rise to complex structures by simultaneous formation of two or more bonds, according to the domino principle, higher productivity, simple procedures, facile execution, and play an important role in combinatorial chemistry. Among a large variety of nitrogen-containing heterocyclic compounds, heterocycles containing an urazole moiety are of interest because they constitute an important class of natural and non-natural products, many of which exhibit useful some biological as well as pharmaceutical activity. 1-hydroxy-2-naphtoic acid and 3-hydroxy-2-naphtoic acid as a ligand were applied for complexation with metal ions under different conditions. The lanthanides were used for the indication of oxygen of hydroxyl of the –COOH group in these compounds. In this work, an efficient, environmentally and high yielding procedure for the one-pot, three-component synthesis of triazolo[1,2-a]indazole-1,3,8-trione derivatives by condensation of dimedone, urazole, and aromatic aldehydes catalyzed by Cu (II) complex was equipped with 3-hydroxy-2-naphtoic acid ligand (Cu-HNA), as an ecofriendly catalyst with high catalytic activity and reusability at 100°C under solvent-free conditions is reported. The reaction proceeds to completion within 30–40 min in 82–92% yield.