Synthesis of 2-Substituted Imidazoles and Benzimidazoles and of 3-Substituted Pyrazoles by Lithiation of N-(Dialkylamino)methyl Heterocycles

Article abstract of DOI:10.1021/jo00259a014

The lithiation of N-(dialkylamino)methyl (aminal) derivatives of imidazole, benzimidazole, and pyrazole (themselves readily available from parent heterocycles, formaldehyde, and a secondary amine) occurs smoothly at 2-, 2-, and 5-positions, respectively, upon treatment with n-butyllithium in ether or tetrahydrofuran.Reaction with electrophiles, and subsequent facile acid-catalyzed hydrolysis of the protecting group, provides 2-substituted imidazoles, 2-substituted benzimidazoles, and 3(5)-substituted pyrazoles in good overall yields.