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 (<strong>ThP₂W₂₂</strong>) was successfully synthesized and characterized, which is constructed from two mono-lacunary Keggin-type [PW₁₁O₃₉]^7- units bridged by an eight-coordinate Th⁴⁺ ion. <strong>ThP₂W₂₂</strong> demonstrates exceptional catalytic activity as a Lewis acid catalyst in the synthesis of 2,3-dihydroquinazolinones <em>via</em> cyclization of 2-aminobenzamides with aldehydes. Various quinazolinones were synthesized in excellent yield (75%-92%) under mild and green reaction conditions. Control experiments confirm the synergistic role of Th⁴⁺ and the polyoxometalate framework in enhancing catalytic efficiency, highlighting thorium-containing polyoxometalate as a promising catalyst in heterocycle synthesis.