Electrochemical and EPR characterization of 1,4-dihydropyridines. Reactivity towards alkyl radicalsReport as inadecuate




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This work reports the electrochemical oxidation of a series of three synthesized 4-substituted-1,4-dihydropyridine derivatives in different electrolytic media. Also, an EPR characterization of intermediates and the reactivity of derivatives towards ABAP-derived alkyl radicals are reported.Dynamic, differential pulse and cyclic voltammetry studies on a glassy carbon electrode showed an irreversible single-peak due to the oxidation of the 1,4-dihydropyridine 1,4-DHP ring via 2-electrons to the corresponding pyridine derivative.Levich plots were linear in different media, indicating that the oxidation process is diffusion-controlled. Calculated diffusion coefficients did not exhibit significant differences between the derivatives in the same medium.The oxidation mechanism follows the general pathway electron, H + , electron, H + with formation of an unstable pyridinium radical. One-electron oxidation intermediate was confirmed with controlled potential electrolysis CPE and EPR experiments. On applying N-tert-butyl-alpha-phenylnitrone PBN and 5,5-dimethyl-1-pyrroline N-oxide DMPO as the spin trap, these unstable radical intermediates from the oxidation of 1,4-DHP derivatives were intercepted. The final product of the CPE, i.e. pyridine derivative, was identified by GC-MS technique.Direct reactivity of the synthesized compounds towards alkyl radicals was demonstrated by UV-Vis. spectroscopy and GC-MS technique. Results indicate that these derivatives significantly react with the radicals, even compared with a well-known antioxidant drug such as nisoldipine.



Author: López Alarcón, Camilo Ignacio; - Camargo Grandón, Rodrigo; - Navarrete Encina, Patricio; - Atria Salas, Ana María; - Squella

Source: http://repositorio.uchile.cl/



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