Synthesis and practical applications of 2-(2-nitroalkyl) pyrroles

Functionalization of pyrroles introducing a 2-nitroalkyl moiety allows the formation of nitro-containing compounds to be used as pivotal intermediates for the synthesis of bioactive compounds. Reaction of pyrroles with nitroalkenes under the Friedel–Crafts conditions, allows a direct entry to 2-(2-nitroalkyl) pyrroles. This approach can be also used for the preparation of enantioenriched derivatives exploiting asymmetric catalysis. In a complementary fashion, the Henry reaction between 2-formylpyrroles and nitroalkanes generates the corresponding nitroaldol products which upon dehydration and reduction of the intermediate 2-pyrrolylnitroethene efficiently afford 2-(2-nitroalkyl) pyrroles. This review article summarizes the most relevant procedures for the preparation of 2-(2-nitroalkyl) pyrroles during the last two decades as well as their significant practical applications.