Organo-photocatalytic Synthesis of Functionalized Pyrroles from 2H-Azirines and α-Substituted Nitroalkenes

An efficient organo-photocatalytic method for the synthesis of tetrasubstituted pyrroles bearing a ketone, ester, alcohol, or nitro group at the 3-position has been developed. The reaction involves visible-light-mediated formal [3+2] dipolar cycloaddition between 2H-azirines and α-substituted nitroalkenes followed by a denitration or debromination sequence. The notable features of the protocol are excellent regioselectivity, wide substrate scope, and high yields of the products.