Enantioselective β-alkylation of pyrroles with the formation of an all-carbon quaternary stereocenter

Abstract

A substitutionally and configurationally inert octahedral chiral-at-metal iridium complex is reported to be an efficient catalyst for the enantioselective Friedel–Crafts alkylation of 2,5-disubstituted pyrroles at the β-position using nitroacrylates as electrophiles. Catalysis is mediated through the ligand sphere of the bis-cyclometalated iridium complex by forming hydrogen bonds and van-der-Waals interactions with the substrates, providing β-alkylated pyrroles regioselectively in 75–98% yield and with 86–99% enantiomeric excess (19 examples). The products are versatile chiral building blocks as demonstrated by the reduction of the nitro group with complete retention of the chiral information.