Aromatic Nitrogen Donors for Efficient Copper(I)-NHC CuAAC under Reductant-Free Conditions

Copper(I)‐catalysed azide–alkyne cycloaddition (CuAAC) has been successfully conducted under reductant‐free conditions. The catalytic system consisted of a combination of a copper(I)–N‐heterocyclic carbene complex and aromatic N‐donors. The catalyst is stable and can be stored, thus rendering the reaction valuable for routine use. The alliance of a copper(I)–N‐heterocyclic carbene with 4,7‐dichloro‐1,10‐phenanthroline allows efficient copper(I)‐catalysed azide–alkyne cycloaddition (CuAAC) at 1 mol‐% loading in the absence of reducing agents. The catalyst is stable and can be stored, thereby allowing easier routine use.