An Unusual Activity of Conformationally Restricted Naphthalene Peri-Dichalcogenides in the Reduction of Nitro and Azide Groups.

Abstract

Rigid and conformationally restricted dichalcogenides based on 1,8-naphthyl system have attracted significant interest as electron donors in charge transfer complexes and organic electrode materials. Recently, naphthalene-1,8-peri-diselenides have been shown to mimic the function of two major selenoenzymes - iodothyronine deiodinase (Dio) and glutathione peroxidase (GPx) - mainly through two-electron redox processes involving deiodination of thyroid hormones and thiol-mediated reduction of hydrogen peroxide, respectively. Herein, we report that naphthalene-1,8-peri-dichalcogenides can mediate a six-electron reduction of organic nitro compounds to produce the corresponding primary amines at physiologically relevant temperature (37 °C) using water as the solvent. The stepwise reduction process is highly dependent on the nature of the chalcogen atom present at the peri-positions of the naphthyl ring. While no reduction was observed with the disulfide, the selenenyl sulfide mediated a four-electron reduction of the nitro group to the corresponding hydroxylamine. The diselenide and ditelluride reduced the nitro groups all the way to amines through six-electron transfer. The diselenides also mediated the reduction of various aromatic azides to the corresponding primary amines.