ORGANIC
LETTERS
2010
Vol. 12, No. 22
5281-5283
Fast, Efficient, Mild, and Metal-Free
Synthesis of Pyrroles by Domino
Reactions in Water
Magnus Rueping* and Alejandro Parra
Institute of Organic Chemistry, RWTH Aachen UniVersity, Landoltweg 1,
D-52074 Aachen, Germany
Received September 19, 2010
ABSTRACT
(E)-ꢀ-Bromonitrostyrenes react with enaminones in water to afford pyrroles in excellent yields. The domino reaction constitutes a new, mild,
and environmentally benign process for the fast and efficient synthesis of diverse pyrroles.
Among the many heteroaromatic compounds, the pyrrole ring
has found a wide number of applications and is present in
many natural products.1 It is used as an important skeleton
in organic synthesis2 and is also utilized in other important
fields, such as materials science,3 medicinal chemistry, and
pharmacology.4 Therefore, a large effort has been made to
develop more efficient synthetic routes to obtain this valuable
heterocycle.5 The most frequently used methods are the
classic Hantzsch,6 Knorr,7 and Paal-Knorr8 procedures.
Although these methods have been used during the last
century, there are significant drawbacks which have triggered
the search for new methodologies, such as multicomponent
couplings9 and transition-metal-catalyzed cyclizations.10 The
success of these newer methods is often limited as in many
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10.1021/ol102247n 2010 American Chemical Society
Published on Web 10/27/2010