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Issue 11, 2018
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Absolute and relative facial selectivities in organocatalytic asymmetric chlorocyclization reactions

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Abstract

Though (DHQD)2PHAL-catalyzed chlorocyclizations of 1,1-disubstituted olefins show useful (and in some cases, reversible) asymmetric induction, stereochemically complete descriptions of these alkene additions have remained largely unknown. Herein, based on a combination of NMR, derivative, isotope labeling, and computational studies, we present detailed stereochemical analyses of chlorocyclizations of nucleophile-tethered 1,1-disubstituted styryl systems. The selectivities of the two asymmetric bond-forming processes, namely electrophilic chlorine attack and nucleophilic ring closure, are thus mapped out independently. Under the established optimal conditions, four related chlorocyclizations were subjected to this analysis. All showed a strong preference for Cl+ delivery from the same face of the alkene. However, depending on reaction conditions and substrate identity (carboxylic acid, amide or carbamate), the internal nucleophiles may close with a strong net preference for either syn or anti addition relative to the Cl atom. Studies of both uncatalyzed and (DHQD)2PHAL-catalyzed processes place new boundary conditions on the role of the catalyst in these reactions.

Graphical abstract: Absolute and relative facial selectivities in organocatalytic asymmetric chlorocyclization reactions

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Publication details

The article was received on 12 Oct 2017, accepted on 24 Dec 2017 and first published on 02 Jan 2018


Article type: Edge Article
DOI: 10.1039/C7SC04430E
Citation: Chem. Sci., 2018,9, 2898-2908
  • Open access: Creative Commons BY license
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    Absolute and relative facial selectivities in organocatalytic asymmetric chlorocyclization reactions

    N. Salehi Marzijarani, R. Yousefi, A. Jaganathan, K. D. Ashtekar, J. E. Jackson and B. Borhan, Chem. Sci., 2018, 9, 2898
    DOI: 10.1039/C7SC04430E

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