H. Bonacorso, Jussara Navarini, Liliane M. F. Porte
Jul 1, 2013
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Journal
Journal of Fluorine Chemistry
Abstract
Abstract This paper describes firstly the synthesis of a new series of 3-hydroxy-2-[(3(5)-(methyl/phenyl)-5(3)-(trifluoromethyl)-1 H -pyrazol-4-yl)arylmethyl]-cyclohex-2-en-1-ones (2), where aryl = C 6 H 5 , 4-NO 2 C 6 H 4 , 4-OCH 3 C 6 H 4 , from an ANRORC ring transformation reaction of 3-acyl-4-aryl-2-(trifluoromethyl)-2-hydroxy-3,4,7,8-tetrahydro-2 H -chromen-5(6 H )-ones (1), where acyl = acetyl and benzoyl, in the presence of hydrazine hydrate, at 63–90% yields. In subsequent steps, an oxidative aromatization reaction from 2 was done in an iodine/methanol medium for the preparation of 3(5)-trifluoromethyl-5(3)-methyl-4-[(2,6-dimethoxyphenyl)-(4-methoxyphenylmethyl)]-1 H -pyrazole (3) at 72% yields. Also, the alkylation reaction using benzyl chloride easily converted a pyrazole like 2 to its N -benzyl derivative (4), at 69% yield. Finally, the structural assignment of compounds 2–4 was deduced by mass spectrometry, X-ray crystal diffraction and density functional theory (DFT) calculations, which clearly and unambiguously furnished values very close to those determined from 1 H, 13 C and 19 F NMR data.