Transition Metal-Catalyzed C–H Functionalization of Imidazo-fused Heterocycles

Abstract

Imidazole-fused heterocycles constitute an interesting class of privileged chemical entities found in natural products, and form the backbone for the construction of complex organic architectures with profound applications in medicinal and materials chemistry. We present herein a compilation of significant advancements made towards transition metal-catalyzed C–H functionalization of various imidazo-fused heterocycles for the one-pot atom-economical C–C, C–S/Se, C–N, C–P and C–Si bond formations. In particular, C( sp 2 )-arylation/heteroarylation, C( sp 2 )-alkenylation and C( sp 2 )-alkynylation at different positions have been achieved in thoroughly investigated imidazo[1,2- a ]pyridines, imidazo[2,1- b ]thiazoles and benzo[ d ]imidazo[2,1- b ]thiazoles prominently under palladium(II)-catalysis, while chacogenylation has been achieved primarily at the expense of inexpensive copper(I)/copper(II)-catalysis; though the other transition metal catalysts such as nickel(II), rhodium(II), ruthenium(II), vanadium(IV), and manganese(II). Iron(II), iron(III), iridium(III), and zinc(II) have proven their repute for selective C–H functionalizations with different coupling partners