Electrochemical Oxidation of Organic Amides

Amide bonds are considered to be stable and therefore, difficult to break. So far, electrochemical oxidation of amides and lactams has afforded almost exclusively products stemming from alkoxylation (in alcohols) and acyloxylation (in acetic and formic acids) products at the α-position to nitrogen [1].

Anodic oxidation of ArNCOCH₂Ph in acetonitrile affords low currents and not effective. The minor products obtained do not stem from a cleavage of the benzylic (PhCH₂-CO) bond. However, the anodic oxidation of amides with more activated benzylic group such as ArNCOCHPh₂undergo three types of bond-cleavage [2], of which routes A (between the benzylic carbon and the carbonyl group) and C (between the ‘N’ atom and aryl group) prevail, as illustrated below.

The selectivity of the cleavage and nature of emerged products is highly dependent on the nature of substituent attached to the aryl group. The type of products obtained and the mechanism involved will be discussed.

References

[1] S. D. Ross, M. Finkelstein and R. C. Petersen, J. Am. Chem. Soc., 1964, 86, 2745; Ibid., 1966, 88, 4657; M. Finkeistein, K. Nyberg, S. D. Ross and Servin, Acta Chem. Scand., Ser. B, 1978, 32b, 182; M. Lennartz, M. Sadakane and E. Steckhan, Tetrahedron, 1999, 55, 14407.

[2] T. Golub and J.Y. Becker, Org. Biomol. Chem. (OBC), 2012, 10, 3906.