Synthesis of Ethyl Pyrimidine-4-carboxylates from Unsymmetrical Enamino Diketones and Their Application in the First Synthesis of Pyrimido[4,5-d]pyridazin-8(7H)-ones - Rosa, Fernanda A.; Machado, Pablo; Fiss, Gabriela F.; Vargas, Pâmela S.; Fernandes, Tanize S.; Bonacorso, Helio G.; Zanatta, Nilo; Martins, Marcos A. P. (Synthesis, 2008)