12-Tungstoboric acid (H5BW12O40) as an efficient Lewis acid catalyst for the synthesis of chromenopyrimidine-2,5-diones and thioxochromenopyrimidin-5-ones: Joint experimental and computational study

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. Interestingly, this catalyst structure pattern may act as useful model for the design and assembly of the functional molecule-based catalysts, especially in the field of molecular sieve materials. Moreover, thermochemical properties in the synthesis of title compounds were assessed using density functional theory (DFT) calculations.