H. Bonacorso, M. Martins, N. Zanatta
Sep 1, 1999
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Influential Citations
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Journal
Spectroscopy Letters
Abstract
Abstract A new series of trichloromethylated- 4, 5-dihydro-1H-pyrazoles has been studied. The molecular structure of 5-hydroxy-3-phenyl-5-trichloromethyl-4,5-dihydro-7H-pyrazole-1-carboxyamide (2), synthesized from the reaction of 4-methoxy -4-phenyl-1,1,1-trichloro-3-buten-2-one (1) with semicarbazide hydrochloride, was selected and determined by NMR spectroscopy, X-ray diffraction, and semiempirical MO calculations. Proton and carbon-13 NMR data, as one set of signals, shown that only one pair of the enanfiomers was obtained. The AM1 calculations showed that 2a (1S5S/1R5R) is the more stable enantiomers pair. The x-ray diffraction data confirmed that only the structure 2a (1S5S/1R5R) was obtained. This was explained by the existence of an intramolecular hydrogen bond between the hydroxy group at C(5) and the carbonyl group at N(1), with the formation a stable six-membered ring. Compound 2 (C11H10CI3N3O2, Mr = 320.98) crystallizes in the monoclinic space group P21/c with the unit cell dimensions a = 6.49...