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The reaction of unsymmetrical enamino diketones [RC(O)C(=CNMe 2)C(O)CO 2 Et, where R = Ph, 4-MeC 6 H 4 , 4-MeOC 6 H 4 , 4-BrC 6 H 4 , 4-ClC 6 H 4 , 4-FC 6 H 4 , 4-O 2 NC 6 H 4 , 2-thienyl, benzofuran-2-yl, and CF 3 ] with N-C-N dinucleophiles, such as benzamidine hydrochloride or 1H-pyrazole-1-carboxamidine monohydrochloride, afforded a series of ethyl 2,5-disubstituted pyrimidine-4-carboxylates in a chemoselective and highly chemoselective manner (51-86%). Reaction of these two series of pyrimidines (R = Ph, 4-MeOC 6 H 4 , 4-FC 6 H 4 , and 2-thienyl) with hydrazine monohydrate under mild conditions led to 2,5-substituted pyrimido[4,5-d]pyridazin-8(7H)-ones in high yields (81-92%).

Synthesis of Pyrimido[4,5-d]pyridazin-8(7H)-ones -[as products of agrochemical and pharmacological interest]. -(ROSA, F. A.; MACHADO, P.; FISS, G. F.; VARGAS, P. S.; FERNANDES, T. S.; BONACORSO, H. G.; ZANATTA, N.; MARTINS*, M. A. P.; Synthesis 2008, 22, 3639-3648; Dep. Quim., Univ. Fed. Santa Maria, 97105 Santa Maria, Brazil; Eng.) -Mais 13-149