An efficient and green route for the synthesis of dihydropyrimidinones via microwave-assisted Biginelli reaction catalyzed by 3 mol% of heteropolyanion-based ionic liquids under solvent-free conditions has been reported. The practical reaction was found to be compatible with different structurally diverse substrates. Good to excellent yields, short reaction times, and operational simplicity are the main highlights of this protocol. Moreover, the heteropolyanion-based ionic liquids were easily reusable for this Biginelli reaction. GRAPHICAL ABSTRACT

A heteropolyanion-based ionic liquid catalyzed oxidative amidation of aldehydes with amines via a dual-catalysis pathway has been reported.

Efficient, eco-friendly and sustainable access to 3,4-dihydropyrimidin-2(1H)-ones directly from alcohols under microwave and solvent-free conditions has been reported. The practical protocol involves heteropolyanion-based catalyzed oxidation of alcohols to aldehydes with NaNO₃ as the oxidant followed by cyclocondensation with dicarbonyl compounds and urea or thiourea in a two-step, one-pot manner. Compatibility with different functional groups, good to excellent yields and reusable catalysts are the main highlights. The utilization of alcohols instead of aldehydes is a valid and green alternative to the classical Biginelli reaction.

A sustainable procedure for the synthesis of N-heteroaryl amides directly from oxidative amidation of aldehydes catalyzed by heteropolyanion-based ionic liquids under microwave-promoted conditions has been reported. The transformation has proven to tolerate a wide range of aldehydes and amino heterocycles with different functional groups. Moderate to excellent yields, solvent-free media, operational simplicity and reusability of catalysts are the main highlights. Furthermore, the proposed N-directing dual-catalysis mechanistic pathway was briefly investigated in this report.