Catalytic C-H arylation of SEM-protected azoles with palladium complexes of NHCs and phosphines.

[reaction: see text] The synthesis and catalytic evaluation of palladium complexes containing imidazolyl carbene ligand of varying steric and electronic properties is reported. These complexes catalyze the efficient C-H arylation of SEM-protected azole heteroarenes and thus provide a good method for preparation of a wide range of arylated free (NH)-azoles including pyrroles, indoles, imidazoles, and imidazo[1,2-a]pyridines. The reaction is operationally simple; the complexes are insensitive to moisture.