Synthesis of new organic-inorganic hybride of Kit-6-NH2@Vanillin@α-methyleneacetophenone@ acridine-Cu(ꟾ) as a recoverable Lewis acid catalyst and its application for the synthesis of azoacridines

Kit-6-NH₂@Vanillin@ α-methyleneacetophenone @ acridine-Cu (ꟾ) nanoparticles were synthesized and were characterized completely. Then, the application of this new nano catalyst for the preparation of azo-derived dihydropyridines (acridines) via the treatment between dimedone, aldehydes, and 4-aminoazobenzene was investigated. The procedure proceeded in suitable yield and good reaction speed. Easy preparation of the catalyst, simple isolation and use of solvent-free condition are the main advantages of the protocol. The nanocatalyst can be reused for nine reaction cycles with no notable decrease in catalytic efficiency.

Background

1,4-Dihydropyridine (DHP) derivatives are used in medicines and other products. After Hantsch method for the synthesis of DHPs, various modifications were carried out on this method such as using different catalysts in refluxing solvent, under ultrasound irradiation, microwave condition, and solvent-free procedure. These methods suffer from many problems such as: use of complex reagents, high consumption of solvent, long time and in some cases low reaction efficiency. While some methods work well, it is important to find a better catalyst for making 1,4-DHPs.

Method

1 mmol of 4-aminoazobenzene, 1 mmol of aldehyde, 2 mmol of dimedone and 0.05 g of catalyst were mixed and was stirred at room temperature. The reaction progress was controlled by TLC (4:1 Ethylacetate:n-hexane). After required reaction time monitored by TLC, 10 mL of hot EtOH was added to mixture. The catalyst was separated by filtration and reused for successive run.

Key finding

This is the first report for the synthesis of azo-linked dihydropyridines using Kit-6-NH₂@Vanillin@α-methyleneacetophenone@ acridine-Cu(I). Shorter reaction time and higher yield rather than most of reported methods are two major benefits of this work. The reaction was carried out under solvent-free condition and there is no need to use organic and hazardous solvents in this procedure. The reaction was carried out at room temperature that need no heating and it is based on green chemistry rules because is energy-economical.