Tandem Synthesis of Polysubstituted Pyrroles via Cu(I)-Catalyzed Cyclization of Ketene <i>N,S</i>-Acetals with β-Ketodinitriles

A new approach to multifunctionalized pyrroles has been explored by the tandem cyclization of α-oxoketene-<i>N</i>,<i>S</i>-acetals with β-ketodinitriles using Cu(MeCN)₄BF₄ and Ag₂CO₃ in toluene under reflux conditions. The reaction involves C-C/C-N bond creation, and is assumed to proceed via enamine formation, intramolecular cyclization, and rearrangement. The potential of the methodology has also been demonstrated for a gram-scale reaction as well as for some useful organic transformations. The reaction offers a practical pathway to achieve polysubstituted pyrroles with broad substrate scope and good functional group tolerance.