Electrolytic oxidation of C4-nitrofuryl 1,4-dihydropyridines in nonaqueous medium
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A study of the electrolytic oxidation of three new C-4 nitrofuryl 1,4-dihydropyridines in nonaqueous aprotic medium is presented. Controlled-potential electrolysis (CPE) in dimethylformamide +0.1 M tetrabutyl-ammonium hexafluorophosphate (TBAPF(6)) was followed by UV-visible spectroscopy, high-performance liquid chromatography (HPLC)-photodiode array (PDA), and gas chromatography-Mossbauer spectroscopy (GC-MS) chromatography, and electron spin resonance and electrochemical techniques. Carbon-centered radical intermediates produced in the electrochemical oxidation of C-4 nitrofuryl substituted 1,4dihydropyridines were trapped with N-benzylidene-tert-butylamine-N-oxide (PBN) and their splitting constants were calculated. The neutral pyridine derivatives were identified by GC-MS techniques as final oxidation products. HPLC-PDA and GC-MS chromatographic techniques were used to follow the time-course of CPE of both parent 1,4-DHP derivatives and their respective oxidation products. Also, an overall oxidation mechanism of C-4 nitrofuryl-1,4-DHP derivatives is presented.