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Issue 39, 2019
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Synthesis of new cyclazines and 4,5-diaryl-1H-pyrrol-3(2H)-one units in discoipyrroles from indolizinone-DMAD cycloadducts

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Abstract

The reaction of indolizinones with dimethyl acetylenedicarboxylate gave direct access to 3′,8a-dihydrocyclopenta[hi]indolizin-8a-ol and 1H-pyrrol-3(2H)-one in good yields. The former skeleton is a precursor to cyclazines with nitrogen on the periphery, a hitherto un-accessed 10-π system. Their formation involves initial [4 + 2] or [8 + 2] modes of cycloadditions; the retro-Diels Alder reaction of the [4 + 2] cycloadduct leads to 1H-pyrrol-3(2H)-one, whereas [8 + 2] addition followed by π-reorganization leads to the azatricyle. Analysis of substituent effects on product distribution showed that electron donating groups on the C3-aryl ring promote the formation of the azatricycle preponderantly. Treatment of one of these azatricycles (3c) with HBF4 led to the formation of the corresponding 10e-aromatic species which was detected by NMR spectroscopy. In addition, formation of the 1H-pyrrol-3(2H)-one skeleton through the normal retro-Diels Alder pathway was employed in the total synthesis of Discoipyrrole C, which is a new lead against lung cancer.

Graphical abstract: Synthesis of new cyclazines and 4,5-diaryl-1H-pyrrol-3(2H)-one units in discoipyrroles from indolizinone-DMAD cycloadducts

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Supplementary files

Article information


Submitted
26 Jul 2019
Accepted
18 Sep 2019
First published
18 Sep 2019

Org. Biomol. Chem., 2019,17, 8832-8848
Article type
Paper

Synthesis of new cyclazines and 4,5-diaryl-1H-pyrrol-3(2H)-one units in discoipyrroles from indolizinone-DMAD cycloadducts

J. Kurian and M. K. M., Org. Biomol. Chem., 2019, 17, 8832
DOI: 10.1039/C9OB01655D

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