An Efficient Synthesis of Pyrano[c]chromenediones and [1,3]Dioxolo[g] chromeneones Catalyzed by Nickel(II) Chromite Nanoparticles Through a Three-Component Domino Reaction.

Abstract

Due to the importance of fused chromene motifs in bioactive compounds, the current research aimed to explore novel methods for the construction of heterocyclic scaffolds. Regarding the attractive features of developing novel methodological approaches in the presence of heterogeneous nanocatalysts, we will try to synthesize 4-aryl-3,4-dihydro-2H,5H-pyrano[3,2- c]chromene-2,5-diones and 8-aryl-7,8-dihydro-6H-[1,3]dioxolo[4,5-g]chromene-6-ones. The aim of the present research was to prove the catalytic efficiency of the synthesized nickel(II) chromite nanoparticles (NiCr2O4 NPs) as bifunctional Lewis acid-Lewis base catalyst in the synthesis of pyrano[c]chromenediones and [1,3]dioxolo[g]chromeneones. Pyrano[c]chromenediones and [1,3]dioxolo[g]chromeneones were conveniently prepared from a three-component condensation reaction between aromatic aldehydes, Meldrum's acid, and active methylene compounds including 4-hydroxycoumarin or 3,4-methylenedioxyphenol using NiCr2O4 NPs as an efficient, readily available, and recyclable catalyst, under ethanol-drop grinding at room temperature. The synthesized compounds were characterized by IR, 1H, and 13C NMR spectroscopy and also by elemental analyses. A number of 4-aryl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-diones and 8-aryl- 7,8-dihydro-6H-[1,3]dioxolo[4,5-g]chromene-6-ones were effectively synthesized as target compounds in high yields. This study provides a simple, inexpensive, and NiCr2O4 NPs catalyzed route to synthesis pyrano[c]chromenediones and [1,3]dioxolo[g]chromeneones in high yields. The reaction offers several benefits, including simple experimental procedures, higher yields, shorter reaction times, and the use of easily obtained and recyclable catalyst compared with previously reported methods and has a great scope for development.