A series of N-heterocyclic carbene precursors, containing an imidazoline or tetrahydropyrimidine framework, were prepared from omega-chloroalkanoyl chlorides. The sequential attachment of nitrogen nucleophiles and subsequent ring closure gave, depending on the reagents used, either the desired dihydroimidazolium and tetrahydropyrimidinium salts or their parent heterocycles. In this latter case, the second substituent was introduced in an alkylation step. The preparation of carbene precursors bearing chiral or bulky substituents was acieved with comparable efficiency.

A series of different N-heterocyclic carbenes (NHCs) were reacted with 3,6-bis(3',5'-dimethylpyrazolyl)-tetrazine in the presence of an inorganic carbonate to provide access to a hitherto unprecedented compound class. The formed tetrazine derivatives bearing the NHC in the 3-position and an oxygen in the 6-position show a quinoidal-like structure, according to physical examinations and X-ray crystallography.