Chiral chalcogen bond donors based on the 4,4'-bipyridine scaffold

Organocatalysis through chalcogen bonding (ChB) is in its infancy, as its proof-of-principle
was only reported in 2016. Herein, we report the design and synthesis of new chiral ChB donors, as well
as the catalytic activity evaluation of the 5,5'-dibromo-2,2'-dichloro-3-((perfluorophenyl)selanyl)-
4,4'-bipyridine as organocatalyst. The latter is based on the use of two electron-withdrawing groups,
a pentafluorophenyl ring and a tetrahalo-4,4'-bipyridine skeleton, as substituents at the selenium
center. Atropisomery of the tetrahalo-4,4'-bipyridine motif provides a chiral environment to these new
ChB donors. Their synthesis was achieved through either selective lithium exchange and trapping or
a site-selective copper-mediated reaction. Pure enantiomers of the 3-selanyl-4,4'-bipyridine were
obtained by high performance liquid chromatography enantioseparation on specific chiral stationary
phase, and their absolute configuration was assigned by comparison of the measured and calculated
electronic circular dichroism spectra. The capability of the selenium compound to participate in
-hole-based interactions in solution was studied by 19F NMR. Even if no asymmetric induction has
been observed so far, the new selenium motif proved to be catalytically active in the reduction of
2-phenylquinoline by Hantzsch ester.