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Issue 44, 2017
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Stereochemistry and mechanistic insights in the [2t + 2i + 2i] annulations of thioketenes and imines

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Abstract

Stereochemical models and mechanistic insights are proposed for [2t + 2i + 2i] annulations of thioketenes and imines on the basis of experimental and computational investigations. In the [2t + 2i + 2i] annulations involving cyclic imines, the zwitterionic intermediates generated from monosubstituted thioketenes and the cyclic imines undergo a stepwise nucleophilic endo-addition/Si-face attack pathway with a second imines molecule, giving initially (2,4)-cis-(4,5)-cis-[2t + 2i + 2i] annuladducts, which completely epimerize into the corresponding (2,4)-cis-(4,5)-trans-annuladducts under basic reaction conditions. The annuloselectivity of thio-Staudinger cycloadditions is dependent on the substituents of both thioketenes and imines. The reactivities and annuloselectivities of Staudinger, thio-Staudinger, and sulfa-Staudinger intermediates are compared.

Graphical abstract: Stereochemistry and mechanistic insights in the [2t + 2i + 2i] annulations of thioketenes and imines

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Publication details

The article was received on 03 Sep 2017, accepted on 27 Oct 2017 and first published on 27 Oct 2017


Article type: Paper
DOI: 10.1039/C7OB02212C
Citation: Org. Biomol. Chem., 2017,15, 9424-9432
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    Stereochemistry and mechanistic insights in the [2t + 2i + 2i] annulations of thioketenes and imines

    W. He, J. Zhuang, H. Du, Z. Yang and J. Xu, Org. Biomol. Chem., 2017, 15, 9424
    DOI: 10.1039/C7OB02212C

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