Organosulphur and organoselenium ligands in designing metal-based catalytic systems for C-H arylation of imidazole

Structural units substituted with imidazole motif play significant roles in many functional and biologically active molecules. Such units are important for naturally occurring chemicals, agrochemicals, medicines, and materials. An effective procedure employed for derivatizing imidazole is the arylation of C-H bond with a high degree of regioselectively. C-4 carbon in imidazole is the least preferred site of the C-H arylation reaction. However, the C-2 and C-4 carbon centres are highly susceptible sites for arylation of imidazole. In recent years, palladium catalyzed direct coupling of imidazole and its derivatives with haloarenes has been developed. The present article aims to cover recent developments pertaining to the catalysis of C-H functionalization of imidazoles by sulphur and/or selenium-ligated palladium (II) complexes. Substrate scope of such reactions has been summarized. Variations in catalytic potential due to ligand binding mode, chalcogen donor, and other factors/features of the ligand are critically analyzed.