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Synfacts 2007(8): 0808-0808  
DOI: 10.1055/s-2007-968799
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart · New York

Symmetric 3,4-Disubstituted Pyrroles via Piloty-Robinson Synthesis

Contributor(s): Victor Snieckus, Jignesh J. Patel
B. C. Milgram, K. Eskildsen, S. M. Richter, W. R. Scheidt, K. A. Scheidt*
Northwestern University, Evanston, University of NOtre Dame and Abott Laboratories, North Chicago, USA
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Publication History

Publication Date:
24 July 2007 (online)

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Significance

A very short, concise, and cost-effective synthesis of symmetrical 3,4-disubstituted pyrroles using the Piloty-Robinson reaction is reported. Thus, condensation of aldehydes with hydrazine produces the symmetrical azines which upon acylation lead to bis(enamine) intermediates. Subsequent [3,3]-sigmatropic rearrangement to 1,4-bis(imine), cyclization, and aromatization lead to the 3,4-substituted pyrrole products. The micro­wave reaction conditions allow a very short reaction time for the overall transformation. The scope of the reaction in terms of R and Ar substi­tuents was insufficiently explored.