Silica-Supported Alginic Acid-L-Glutamic Acid: An Efficient Heterogeneous Catalyst for Solvent-free Synthesis of 1,8-Dioxohexahydroacridine and Polyhydroquinoline Derivatives

4-Substituted 1,4-dihydropyridine (1,4-DHP) nucleus is a fertile source of biologically important molecules possessing various important pharmacological properties such as antihypertensive, anti-therosclerotic, hepto-protective, anti-mutagenic, vasodilator, bronchodilator, antitumor, geroprotective and anti-diabetic agents. Thus, these compounds are analogues of NADH coenzymes, which have been investigated for their calcium channel activity and the heterocyclic rings are found in variety of bioactive compounds. Therefore we report herein a convenient and environment-friendly approach for the synthesis of biologically active substituted Hantzsch 1,8-dioxohexahydroacridine and polyhydroquinoline derivatives via a one-pot pseudo four component reaction of various aldehydes, ammonium acetate, cyclic 1,3-dicarbonyl compounds and ethyl acetoacetate in the presence of silica-supported alginic acid-L-glutamic acid (SiO₂-AA-L-Glu) as a new, heterogeneous and essential catalyst is reported under solvent-free conditions at 100 °C. In recent years heterogeneous catalysts have attracted a great attention due to efficiency, and for economic and environmental reasons. SiO₂-AA-L-Glu has been prepared by a simple method to act as a efficient catalyst with high catalytic activity and reusability for the synthesis of biologically active substituted Hantzsch derivatives under thermal condition. The proposed methodology is suitable for producing the desired products in good to excellent yields with short reaction time and straightforward workup.