Synthesis of Collidine from Dinitrogen via a Tungsten Nitride

The synthesis of pyridines from dinitrogen in homogeneous
solution
is known to be challenging considering that an N2 cleavage
step needs to be combined with two N–C coupling steps. Herein,
a tungsten complex bearing a tailor-made 2,2′-(tBu2As)2-substituted tolane
ligand scaffold was shown to split N2 to afford the corresponding
tungsten nitride, which is not the case for the corresponding (iPr2As)2-substituted
derivative. The former nitride was then reacted with 2,4,6-trimethylpyrylium
triflate, which led to the formation of a tungsten oxo complex, along
with collidine. Over the course of this reaction, the O atom of the
pyrylium starting material was replaced with an N atom via a hitherto
unprecedented skeletal editing process.