On the electrochemical behaviour of Nifedipine and related compounds: instability of the reduction products in protic media

Abstract

The electrochemical behaviour of nifedipine and of the analogous 3,5-dicarbethoxy-2,6-dimethyl-4(2-nitrophenyl)-1,4-dihydropyridine has been investigated in protic media. The nitroso derivative (2e − reduction) can be prepared in a redox flow cell; whatever the acidity of the supporting electrolyte, it is unstable and rearranges into indole ( VIII). The amine (6e − reduction) is obtained by electrolysis at very negative potential, in an acetic buffer; in more acidic media, transformation takes place into 3-carboalcoxy-2-methyl quinoline ( VI). The phenylhydroxylamine (4e − reduction) is prepared by controlled potential electrolysis in an acetic buffer; in more acidic media, disproportionation occurs giving a mixture of VIII and VI. ▪ A similar behaviour is observed for the N-methyl derivative of nifedipine; however, the corresponding hydroxylamine does not disproportionate in acidic medium but gives rise to the N-oxide derivative of the quinoline ( VI).