Electrolytic Oxidation of C4-Nitrofuryl 1,4-Dihydropyridines in Nonaqueous Medium

Abstract

A study of the electrolytic oxidation of three new C-4 nitrofuryl 1,4-dihydropyridines in nonaqueous aprotic medium is presented. Controlled-potential electrolysis ͑CPE͒ in dimethylformamide +0.1 M tetrabutyl-ammonium hexafluorophosphate ͑TBAPF 6 ͒ was followed by UV-visible spectroscopy, high-performance liquid chromatography ͑HPLC͒-photodiode array ͑PDA͒, and gas chromatography-Mössbauer spectroscopy ͑GC-MS͒ 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 ͑PBN͒ 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.