The air- and water-stable 1

3-disubstituted imidazol(in)ium-2-carboxylates(NHC—CO2) as important precursors of N-heterocyclic carbenes were prepared by three routes.Nine kinds of  NHC—CO2 with different groups on nitrogen atoms were obtained.The structure was characterized by 1H NMR

elemental analysis and IR.Thermogravimetric analysis(TG/DTG) provided the evidence for decarboxylation in NHC—CO2.The results show that CO2  escapes from the molecule in the process of elevating temperature and free carbenes are released.Two processes(decarboxylation and decomposition) occur when the substituents on the nitrogen atoms are aryl group

and the imidazolium-2-carboxylates and the imidazolinium-2-carboxylates show similar performance of decarboxylation.The initial temperatures of mass loss are lower when the substituents on the nitrogen atoms are alkyl group

and no decomposition occurs.