Pyrroles

Reaction of pyrrole with electrophiles

Pyrroles react easily with nitrating (e.g. HNO₃/Ac₂O), sulfonating (Py·SO₃), and halogenating (e.g. NCS, NBS, Br₂, SO₂Cl₂, and KI/H₂O₂) agents. Halogenation generally provides polyhalogenated pyrroles, but monohalogenation can be performed. As is typical for electrophilic additions to pyrroles, halogenation generally occurs at the 2-position, but can also occur at the 3-position by silation of the nitrogen. This is a useful method for further functionalization of the generally less reactive 3-position.