Use of N-Heterocyclic Carbene Compounds (NHCs) Under Sustainable Conditions—An Update

In this review, we focused on advances made over the last two decades in the field of catalysis using N-heterocyclic carbenes (NHCs), which can be used for metallic or non-metallic catalysis. We listed the advantages of these NHCs and their modes of action in various couplings. With regard to metal catalysis, we have focused here on palladium and nickel catalysis, and then we looked at their use without transition metals. The work mentioned, in this review, only concerns research carried out under sustainable conditions, both in terms of the types of reactions and reaction conditions used (solvents, quantities, accessibility, and easy purification).