Ferrocenyl pyrazolines: Preparation, structure, redox properties and DFT study on regioselective ring-closure |
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Authors: | Virág Zsoldos-Mády Antal Csámpai Dávid Frigyes |
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Institution: | a Protein Modelling Group, Hungarian Academy of Sciences, Eötvös Loránd University, H-1518 Budapest 112, POB 32, Hungary b Institute of Chemistry, Department of Inorganic Chemistry, Eötvös Loránd University, H-1518 Budapest 112, POB 32, Hungary |
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Abstract: | Cyclocondensation of 1-phenyl-3-ferrocenyl-2-propen-1-one (1) with RNHNH2 hydrazines and the substituent-dependent product distribution were investigated. With methylhydrazine, formation of two regioisomeric pairs of pyrazolines and pyrazoles was observed. The ratio of the products varied with the solvent and temperature. Transformation of 5-ferrocenyl-N-substituted pyrazolines into pyrazoles was systematically studied and DDQ was found to be the most suitable reagent. Mechanism of the cyclization reactions taking place under kinetic- and thermodynamic controls was supported with DFT calculations. The energy-dependence of the transformation of pyrazoline to pyrazole was investigated also by EI MS. Structure determination of the new compounds was performed by IR, MS and NMR methods including 2D-HMQC, 2D-HMBC, DEPT and DIFFNOE measurements. For two compounds structures were also proved by X-ray diffraction. |
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Keywords: | Ferrocenes Pyrazoles NMR X-ray MS and IR study DFT calculation |
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