Metal-Induced Cyclization of Thiosemicarbazones Derived from β-Keto Amides and β-Keto Esters: Open-Chain and Cyclized Ligands in Zinc(II) Complexes
- 21 February 2002
- journal article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 41 (6) , 1550-1557
- https://doi.org/10.1021/ic0111942
Abstract
The reactions of Zn(OAc)2 with acetoacetanilide, methyl acetoacetate, o-acetoacetanisidide, and ethyl 2-methylacetoacetate thiosemicarbazones (HTSC1, HTSC2, HTSC3, and HTSC4, respectively) were explored in methanol. With HTSC1, HTSC2, and HTSC3, following isolation of the corresponding zinc(II) thiosemicarbazonates [Zn(TSCx)2] (x = 1, 2, 3), the mother liquors afforded pyrazolonate complexes [ZnL12(H2O)] (HL1 = 2,5-dihydro-3-methyl-5-oxo-1H-pyrazole-1-carbothioamide) that had been formed by cyclization of the corresponding TSC-. The reaction of HTSC4 with zinc(II) acetate gave only the pyrazolonate complex [ZnL22(H2O)] (HL2 = 2,5-dihydro-3,4-dimethyl-5-oxo-1H-pyrazole-1-carbothioamide). All compounds were studied by IR and NMR spectroscopy, and HTSC3, [Zn(TSC3)2]·DMSO, [ZnL12(H2O)]·2DMSO, and [ZnL22(H2O)]·2DMSO were also studied by X-ray diffractometry, giving a thorough picture of the cyclization process. In preliminary tests of the effects of HL1 and [ZnL12(H2O)] on rat paw inflammatory edema induced by carrageenan, HL1 showed antiinflammatory activity.Keywords
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