The “Wanzlick Equilibrium”

1,3-dialkylated benzimidazolin-2-ylidenes are the keys to prove the “Wanzlick equilibrium” between electron-rich tetraaminoethylenes and N-heterocyclic carbenes [Eq. (1)]. This equilibrium was recently discovered by two groups independently. Starting from dibenzotetraazafulvalenes, the equilibrium concentrations in the absence of electrophiles were quantified by NMR spectroscopy.