Protection against Peroxynitrite-Mediated Nitration Reaction by Intramolecularly Coordinated Diorganoselenides

A series of intramolecularly Se···X (X = N, O) coordinated diorganoselenides and -sulfides are
synthesized by using the heteroatom-directed lithiation route and characterized by multinuclear (1H, 13C,
77Se) NMR, IR spectroscopy, and electrospray mass spectrometry (ES-MS). The intramolecular Se···O
interactions in diorganoselenides 26−31 have been studied by multinuclear NMR studies in solution and
in the solid state by single-crystal X-ray crystallography. The protection against peroxynitrite-mediated
nitration reaction (PN assay) by diorganoselenides/-sulfides (with and without intramolecular coordination)
has been evaluated. The PN assay data of diorganoselenides reveal that the selenides 20−22, having a
basic amino group (sp3-N donor) in close proximity of selenium, are more active compared to the
diorganoselenides 16−19, having an imino group (sp2-N donor), and also show much higher protective
action than the unsubstituted diorganoselenides 14 and 15. The diorganoselenides 16−31 were oxidized
to corresponding selenoxides 44−59. The redox properties of the selenoxides 13 and 44−59 have been
investigated by cyclic voltammetry and potentiometric titration experiments. Two redox potentials for in
situ-generated ferrocenyl selenoxides (50, 54−59) were observed. The reduction of selenoxides 13 and
48 to ebselen (2) and selenide 20 with benzenethiol (PhSH) was monitored by ES-MS.