Synthesis of a Molecular Tweezer Based on Norbornadiene Framework: Unexpected Stereoselectivity

In this study, a new type of Klarner tweezer, which has multiple hydrogen bonding acceptors, was synthesized. This tweezer is based on the bicyclo[2.2.1]heptane framework and comprises two near-parallel flat aromatic rings as pincers and a pyrazine unit as the tether. The synthesis was carried out by the annulation of a bicyclic alpha-amino ketone. Surprisingly, this reaction took place stereo-selectively, though the initial alpha-amino ketone starting material was racemic. This unexpected result was explained by theoretical studies.