Regiospecific Cyclization of β-Methoxyvinyl Trifluoromethyl Ketones with Aminoguanidine: A Convenient Method to Obtain Trifluoromethylated 2-[1H-Pyrazol-1-yl]pyrimidines - Bonacorso, Helio Gauze; Wentz, Alexandre Pereira; Zanatta, Nilo; Martins, Marcos Antonio Pinto (Synthesis, 2001)