Continuous Flow Synthesis of Sulfur- and Selenium−NHC Compounds (NHC=N-Heterocyclic Carbene)

The first continuous flow syntheses of sulfur- and selenium−NHC (NHC=N-heterocyclic carbene) adducts in unprecedented short reaction times and high yields are reported. The importance of these species in coordination chemistry or as efficient tools for determining the π-acceptor character of NHC ligands make any improvement in their synthesis a worthy goal. Thiourea derivatives bearing both saturated and unsaturated NHCs were obtained using NEt3 as a weak base (homogeneous setup) in conjunction with a bed of elemental sulfur (S8). The synthetic route proving optimal for selenoureas involves the use of a simple Se/K2CO3 heterogeneous microreactor design.