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Issue 21, 2013
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Symmetric and unsymmetric 3,3′-linked bispyrroles via ring-enlargement reactions of furan-derived donor–acceptor cyclopropanes

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Abstract

A short and concise sequence for the synthesis of symmetrically and unsymmetrically substituted 3,3′-linked bispyrroles is described. Furan as a starting material is subjected to a twofold cyclopropanation by a diazo ester. Conversion of the ester functionalities to the respective ketones is achieved via Weinreb amide formation and the attack of a Grignard reagent. In the presence of amines the ketone moieties form imines that rearrange by ring-enlargement of the three-membered to the five-membered rings. In situ generated dihydropyrrole moieties eliminate water and afford aromatic pyrrole units. Unsymmetric bispyrroles are obtained by using different cyclopropanating agents or varying Grignard reagents for ketone formation before the addition of amines initiates the cascade to the respective bispyrroles.

Graphical abstract: Symmetric and unsymmetric 3,3′-linked bispyrroles via ring-enlargement reactions of furan-derived donor–acceptor cyclopropanes

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Article information


Submitted
01 Feb 2013
Accepted
26 Mar 2013
First published
27 Mar 2013

Org. Biomol. Chem., 2013,11, 3494-3509
Article type
Paper

Symmetric and unsymmetric 3,3′-linked bispyrroles via ring-enlargement reactions of furan-derived donor–acceptor cyclopropanes

J. Kaschel, T. F. Schneider, D. Kratzert, D. Stalke and D. B. Werz, Org. Biomol. Chem., 2013, 11, 3494
DOI: 10.1039/C3OB40228B

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