Rh-Catalyzed Synthesis of N-Aryl Trisubstituted Pyrroles

Significance

A new Rh-catalyzed route to 1,2-diaryl-substituted pyrroles in a three-component assembly reaction is reported. The combination of rhodium(II) salt with excess of diazoacetonitrile leads to the formation of a metallocarbenoid species which, in the presence of an imine, leads to the generation of an azomethine ylide. The reactive ylide intermediate is trapped by an activated acetylene diester in a [3+2] cycloaddition to form the 1,2-diaryl pyrroles in moderate to good yields. Notable is that only 1 mol% catalyst is needed for this transformation.