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Issue 48, 2013
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Development and applications of remote stereocontrol using allylic organobismuth reagents

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Abstract

Reactions of 5-benzyloxy-4-methylpent-2-enyl(tributyl)stannane with aldehydes promoted by bismuth(III) iodide were usefully stereoselective in favour of the (E)-1,5-anti-6-benzyloxy-5-methylalk-3-en-1-ols. Similar stereoselectivity was observed for reactions of analogous 5-benzyloxy-4-methylpent-2-enyl bromides with aldehydes when promoted by a low valency bismuth species prepared by reduction of bismuth(III) triiodide with powdered zinc so providing a “tin-free” procedure. The analogous reactions of 4-benzyloxypent-2-enyl(tributyl)stannane with aldehydes promoted by bismuth(III) iodide were also stereoselective but gave lower yields. Attempted 1,6-stereocontrol using these reactions resulted in only modest stereoselectivities. Aspects of the chemistry of the products were studied in particular their stereoselective conversion into aliphatic compounds with methyl bearing stereogenic centres at 1,5,9,13- and 1,3,5-positions along the aliphatic chain. Mechanistically, allylic organobismuth species may be involved in both sets of reactions but this was not confirmed although the similar stereoselectivities observed for both the bismuth(III) iodide mediated reactions of the pent-2-enylstannanes and the low-valency bismuth promoted reactions of the pent-2-enyl bromides are consistent with participation of similar intermediates.

Graphical abstract: Development and applications of remote stereocontrol using allylic organobismuth reagents

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Publication details

The article was received on 23 Sep 2013, accepted on 30 Oct 2013 and first published on 31 Oct 2013


Article type: Paper
DOI: 10.1039/C3OB41931B
Citation: Org. Biomol. Chem., 2013,11, 8476-8505
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    Development and applications of remote stereocontrol using allylic organobismuth reagents

    N. Basar, S. Donnelly, H. M. Sirat and E. J. Thomas, Org. Biomol. Chem., 2013, 11, 8476
    DOI: 10.1039/C3OB41931B

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