New strategy for the regioselective synthesis of 1-phenyl-3-trifluoromethyl-1H-pyrazoles

作者：Zanatta Nilo^*; Amaral Simone S; dos Santos Josiane M; da Silva Andreia M P W; Schneider Juliana M F M; Fernandes Liana da S; Bonacorso Helio G; Martins Marcos A P

来源：Tetrahedron Letters, 2013, 54(31): 4076-4079.

DOI：10.1016/j.tetlet.2013.05.103

• Pyrazoles
• Trifluoromethylpyrazoles
• Trifluoromethyl enones
• Regioselective synthesis
• Phenylhydrazones

A regioselective synthesis of 3-trifluoromethyl-1-phenyl-1H-pyrazoles (1,3-isomers) as well as their 1,5-isomers (5-trifluoromethyl-1-phenyl-1H-pyrazoles), is described. The 1,3-isomers were obtained from the reaction of 4-alkoxy-1,1,1-trifluoroalk-3-en-2-ones with arylhydrazones followed by deprotective hydrolysis while the 1,5-isomer was obtained by direct cyclocondensation of 4-alkoxy-1,1,1-trifluoroalk-3-en-2-ones with phenylhydrazine. An unequivocal assignment of the 1,3- and 1,5-isomers of the pyrazole products is given.

• 出版日期2013-7-31