933452-60-9Relevant articles and documents
Reductive metalation of cyclic and acyclic pseudopeptidic bis-disulfides and back conversion of the resulting diamidato/dithiolato complexes to bis-disulfides
Desbenoit, Nicolas,Galardon, Erwan,Frapart, Yves,Tomas, Alain,Artaud, Isabelle
, p. 8637 - 8644 (2010)
Cyclic and acyclic pseudopeptidic bis-disulfides built on an o-phenylene diamine scaffold were prepared: (N2H2S2) 2, 1a, N2H2(S-SCH3)2, 1b, and N2H2(S-StBu)2, 1c. Reductive metalation of these disulfides with (PF6)[Cu(CH3CN)4] in the presence of Et4NOH as a base, or with (Et4N)[Fe(SEt) 4] and Et4NCl, yields the corresponding diamidato/dithiolato copper(III) or iron(III) complex, (Et4N) [Cu(N2S2)], 2, or (Et4N)2[Fe(N 2S2)Cl], 5. These complexes display characteristics similar to those previously described in the literature. The mechanism of the metalation with copper has been investigated by X-band electron paramagnetic resonance (EPR) spectroscopy at 10 K. After metalation of the bis-disulfide 1c and deprotonation of the amide nitrogens, the reductive cleavage of the S-S bonds occurs by two one-electron transfers leading to the intermediate formation of a copper(II) complex and a thyil radical. Complexes 2 and 5 can be converted back to the cyclic bis-disulfide 1a with iodine in an 80% yield. Reaction of 5 with iodine in the presence of CH3S-SCH3 affords a 1/1 mixture of the acyclic N2H2(S-SCH3)2 disulfide 1b and cyclic bis-disulfide 1a. From 2, the reaction was monitored by 1H NMR and gives 1b as major product. While there is no reaction of 2 or 5 with tBuS-StBu and iodine, reaction with an excess of tBuSI affords quantitatively the di-tert-butyl disulfide 1c. To assess the role of the Cu III oxidation state, control experiments were carried out under strictly anaerobic conditions with the copper(II) complex, (Et 4N)2[Cu(N2S2)], 6. Complex 6 is oxidized to 2 by iodine, and it reacts with an excess of tBuSI, yielding 1c as final product, through the intermediate formation of complex 2.
