H5BW12O40 (BWA), Keggin-type heteropoly acid was employed as an effective, eco-friendly and reusable Lewis acid catalyst for the high yielding synthesis of chromenopyrimidine-2,5- diones and thioxochromenopyrimidin-5-ones via multicomponent reaction (MCR) of differently substituted benzaldehydes, urea/thiourea, and 4-hydroxycoumarin in refluxing water. The BWA catalyst could be recovered by a simple filtration and applied in three successive runs with no noticeable decrease in the yield. This prolific combination of B atom within Keggin-type polyoxometalates inaugurates a powerful class of porous catalysts for the different chemical transformations, which overcomes key limitations of previously established salts and Lewis acidic metals-based catalysts under low catalyst loading, the use of water scavengers, dry solvents and additives for facilitating the specialized experimental setups commonly employed to the organic reactions. Moreover, thermochemical properties in the synthesis of title compounds were assessed using density functional theory (DFT) calculations.

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