Continuous synthesis and use of N-heterocyclic carbene copper(I) complexes from insoluble Cu2O.

It is demonstrated that homogeneous N-heterocyclic carbene-copper(I)-chloride complexes can be prepared continuously by flowing NHC precursors through a packed bed of solid Cu(2)O suspended in molecular sieves. The method enables the synthesis of a wide range of complexes including those that are challenging to prepare using standard approaches. Our strategy enables both sustained output of complex production for long-term catalytic reactions (greater than 5 h) and for generation of gram quantities for storage (greater than 1 g of complex in ~16 min).