Synthesis and Characterization of Amidato Divalent Lanthanide Complexes and Their Use in Forming 2,4-Quinazolidinones from CO2 and 2-Aminobenzonitriles

Four amidato divalent lanthanide complexes, {L(n)Ln[N(TMS)(2)]THF}(2) [n = 1, Ln = Eu (1); n = 2, Ln = Eu (3), Yb (4); HL1 = tBuC(6)H(4)CONHC(6)H(3)(iPr)(2); HL2 = C6H5CONHC6H3(iPr)(2)] and {(LEu)-Eu-3[N(TMS)(2)]THF}{(L2Eu)-Eu-3(THF)(2)} (2) [HL3 = ClC6H4CONH-C6H3(iPr)(2)], were synthesized and extensively characterized. This is the first time that the amidato lanthanide amides 1-4 were used to catalyze the reactions of CO2 and 2-aminobenzonitriles to form quinazoline-2,4(1H, 3H)-diones at atmospheric pressure. All the complexes efficiently catalyzed the transformation, with complex 3 showing the highest activity. This catalytic system gave good to excellent yields, and good functional group tolerance. Preliminary studies were conducted to investigate the reaction mechanism.