# Friedel-Crafts Alkylation of Pyrrole [duplicate]

I thought that I already know how the Electrophilic Aromatic Substitution (EArs) for Aromatic rings work but then this reaction was shown to me and I was really sure that my professors didn't bothered teaching or even mentioning to us this reaction:

In my defense, at my University, our Org Chem professors always use benzene or benzene derivative rings for demonstration of EArS so I never knew how an acylation of a five-membered aromatic ring works.

Can someone please explain to me how this reaction works?

• Dimethyl acetamide is not a substrate for F-C acylation, are you certain this is a F-C process? – Waylander Sep 1 '19 at 13:56
• @Waylander thank you for noticing, I have edited my question. – Kent de los Reyes Sep 1 '19 at 14:02
• Pretty sure pyrrole isn't amenable towards FC alkylation. It's notoriously prone to polymerisation in the presence of Lewis or Bronsted acid. – orthocresol Sep 1 '19 at 14:04
• If you're interested in why it goes to C-2 rather than C-3, then this is relevant: Regioselectivity in electrophilic substitution of pyrrole – orthocresol Sep 1 '19 at 14:20

To my knowledge, Friedel-Crafts alkylation of pyrrole with aluminum chloride ($$\ce{AlCl3}$$) is unattainable. However, recent literature suggests F-C alkylation of pyrrole with other catalysts is possible. For example, an asymmetric Friedel–Crafts alkylation of pyrrole with nitroalkenes catalyzed by a copper complex of a bisphenol A-derived Schiff base is reported (Ref.1):
Abstract: The asymmetric Friedel–Crafts (FC) alkylation of pyrrole with nitroalkenes was mediated by $$\ce{CuBr2}$$ and a novel bisphenol A-derived chiral catalyst at room temperature. The catalyst was found to be applicable for the asymmetric FC alkylation of pyrrole with a wide range of nitroalkenes, affording optically active alkylated pyrroles with enantioselectivities up to 94%. Furthermore, enantiomerically pure 3-nitro-2-arylpropanamides were prepared by the oxidative cleavage of the pyrrole rings in the FC products with $$\ce{NaIO4/RuCl3}$$ to demonstrate the synthetic application of the products.