Non-conventional green strategies for NHC catalyzed carbon-carbon coupling reactions

Background: Coupling reactions, commonly can be achieved via a wide range of organometallic reagents and electrophiles, representing an important class of synthetic transformation, namely cross-coupling reaction. It is frequently catalyzed by various palladium (Pd) as species. The synthesis and characterization of an N-heterocyclic carbine (NHC) was accomplished in 1991. In 1991, the first synthesis of a stable NHC was achieved and reported. Objective: This development literally invigorated the interest and attention for this novel species being examined as a ligand for the synthesis of Pd Complexes. Conclusion: In this review, we tried to give a full account on the development of NHC–Pd chemistry intended being used as catalyst under non-conventional conditions. In this light, those carbon-carbon bond formations being successfully achieved in aqueous systems, using immobilized NHC-Pd complexes under nonconventional strategies, such as being conducted under microwave irradiations (MWI) are supported and solvent- free conditions are discussed.