Synthesis of new trihalomethylated and non-symmetrical substituted 2-(1H-pyrazolyl)-5-(1H-pyrazolylcarbonyl)pyridines

Abstract

This paper describes the synthesis of a new series of 2-[3-alkyl(aryl/heteroaryl)-5-trifluoro(chloro)methyl-5-hydroxy-4,5-dihydro-1H-pyrazol-1-yl]-5-[3-alkyl(aryl/heteroaryl)-5-trifluoro(chloro)methyl-5-hydroxy-4,5-dihydro-1H-pyrazol-1-yl-1-carbonyl]pyridines by the cyclocondensation reaction of 4-alkoxy-4-alkyl(aryl/heteroaryl)-1,1,1-trifluoro(chloro)-3-alken-2-ones [CX3C(O)CH=CR1OR, where R = Me, Et; R1 = H, Me, Ph, 4-MeOPh, 4-NO2Ph, 4,4'-Biphenyl, 1-Naphthyl, Fur-2-yl, Thien-2-yl and X = F, Cl] with 6-hydrazinonicotinic hydrazide hydrate. Yields of 62 to 97% were obtained when the reactions were performed in ethanol as solvent at 78 °C for 4 hours. In a subsequent step, the dehydration reactions of 2-(5-hydroxy-1H-pyrazol-1-yl)-5-(5-hydroxy-1H-pyrazol-1-yl-1-carbonyl)pyridines were carried out in pyridine/benzene in the presence of thionyl chloride and led to the isolation of a series of 2-[3-alkyl(aryl/heteroaryl)-5-trifluoro(chloro)methyl-1H-pyrazol-1-yl]-5-[3-alkyl(aryl/heteroaryl)-5-trifluoro(chloro)methyl-1H-pyrazol-1-yl-1-carbonyl]pyridines, in 64 to 86% yields. ©2009 Sociedade Brasileira de Química.