The formation of disulfides by the [Fe(nta)Cl2]2− catalyzed air oxidation of thiols and dithiols

The complexes (cnt)2[Fe(nta)Cl2], where nta = nitrilotriacetate and cnt = Et4N+ or PyH+, catalyze the air oxidation of thiols to disulfides under ambient conditions. Dithiols are converted to linear and cyclic oligomers that differ in their terminal groups as a function of the counterion, cnt. Cysteine ethyl ester was converted to the corresponding cystine diethylester in high yield.

Graphical abstractThe iron(III) dichloronitrilotriacetate ion, [Fe(nta)Cl2]2−, catalyzes the air oxidation of thiols and α,ω-dithiols to disulfides and oligomeric disulfides, respectively. Oligomeric products from the oxidation of propane-, butane- and pentanedithiol have been characterized by field desorption mass spectrometry and shown to form monomeric to decameric oligomers. The identity of the oligomer terminal groups is partially dependent on the nature of the catalyst counterion. The [Fe(nta)Cl2]2− ion has been characterized by electrospray mass spectrometry.Figure optionsDownload full-size imageDownload as PowerPoint slide