Imidazole is a common and important heterocyclic fragment of many biologically important molecules. 5-imidazole-carbaldehydes containing mono-(N-1) methyl (or aryl) analogs are commonly used as building blocks in medical chemistry. In this study, starting from 4-methyl-1H-imidazole-5carbaldehyde, the N-1 atom of the imidazole ring is derived with different alkyl groups. In addition, both N atoms of the starting imidazole-carbaldehyde were methylated to give 5-carbaldehyde-1,3,4trimethyl-3-imidazolium salt. The salt which possess quite reactive carbaldehyde group could be used as a precursor for synthesis of other imidazolium derivatives. Furthermore, 4-methyl-5-imidazole carbaldehyde was converted into the benzoxazole, benzothiazole and benzoimidazole by a two-step reaction over the aldehyde group. These new compounds could display some biological activities.