Copper-catalyzed carbene insertion and ester migration for the synthesis of polysubstituted pyrroles

Copper-catalyzed carbene insertion/ester migration/cyclization of enaminones and α-diazo compounds occurred efficiently to afford 2-ester polysubstituted pyrroles under mild conditions in moderate-to-good yields. Substituent functionality was well tolerated and 13 C-labelled experiments demonstrated 1,2-ester migration during the reaction. A mild synthetic protocol to access 2-ester pyrroles through Cu(OTf) 2 -catalysed carbene insertion/ester migration/cyclization of enaminones and α-diazo compounds is reported.