Sandwich-type thorium-substituted phosphotungstate for the catalytic synthesis of aza-heterocycles

A novel sandwich-type thorium-substituted phosphotungstate, [H₂N(CH₃)₂]₁₀[Th(PW₁₁O₃₉)₂]·24H₂O (ThP₂W₂₂), was synthesized and fully characterized. The structure consists of two monolacunary Keggin-type [PW₁₁O₃₉]⁷⁻ units bridged by an eight-coordinate Th⁴⁺ center. ThP₂W₂₂ functions as an efficient Lewis acid catalyst for the synthesis of 2,3-dihydroquinazolinones via cyclization of 2-aminobenzamides with aldehydes. A series of quinazolinone derivatives was obtained in high yields (75%–92%) under mild and green reaction conditions. Control experiments indicate a synergistic interaction between the Th⁴⁺ center and the polyoxometalate framework, highlighting the potential of thorium-containing polyoxometalates as catalysts for heterocycle synthesis.