S -> N and N -> S Reverse Rearrangement of S- and N-(2,4-Dinitrophenyl)cysteines

Article abstract of DOI:10.1021/jo00320a020

The reversible Smiles rearrangement between S-(2,4-dinitrophenyl)cysteine (1a) and N-(2,4-dinitrophenyl)cysteine (2a) has been kinetically studied in methanol, DMF, and Me2SO containing an organic base such as imidazole or DBU.The overall reaction is composed of the spontaneous and base-catalyzed reactions.In methanol the rearrangement from 1a to 2a goes virtually to completion in most cases.In DMF containing DBU, the reverse rearrangement from 2a to 1a becomes observable to afford eventually an equilibrium mixture of 1a and 2a.During this transformation an intermediate was spectroscopically detected, which showed an absorption band around 500 nm.The amide derivative of 1a (1b) failed to undergo a facile rearrangement except under much severer conditions.In this case the normal Smiles rearrangement was accompanied by some side reactions.