Uranyl-silicotungstate-containing hybrid building units {α-SiW9} and {γ-SiW10} with excellent catalytic activities in the three-component synthesis of dihydropyrimidin-2(1H)-ones

A novel uranyl-containing polytungstate, {K4.2Na18.9H0.9(H2O)(20)[K-4(UO2)(3)(H2O)(6)(alpha-SiW9O34)(gamma-SiW10O36)(3)]}ca.16H(2)O (U-3), was synthesized using the Keggin-type precursor [gamma-SiW10O36](8-) ({gamma-SiW10}) and UO2(OAc)(2) and was further characterized by single-crystal X-ray diffraction and various techniques. Single crystal X-ray diffraction analysis showed a quadrahedron-like structure of U-3 with interesting tarot-like (top view) and crown-like (side view) views, among which one central {K-4(UO2)(3)(H2O)(3)} cluster was surrounded by one {alpha-SiW9} and three {gamma-SiW10} building units. In addition, a more significant aspect is that U-3 shows good catalytic activity in the dehydration condensation of aldehydes, acetoacetates, and urea to green synthesize dihydropyrimidin-2(1H)-ones. The advantages of this transformation include solvent-free conditions, water as the sole by-product, available starting materials, good compatibility, and operational simplicity.

Automated summary

A novel uranyl-containing polytungstate, U-3, was synthesized using a Keggin-type precursor and UO2(OAc)2, and characterized by X-ray diffraction and various techniques. U-3 exhibited a quadrahedron-like structure with a central {K-4(UO2)(3)(H2O)(3)} cluster surrounded by {α-SiW9} and {γ-SiW10} building units. Furthermore, U-3 showed good catalytic activity in the dehydration condensation of aldehydes, acetoacetates, and urea to synthesize dihydropyrimidin-2(1H)-ones with solvent-free conditions, water as the sole by-product, available starting materials, good compatibility, and operational simplicity.