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Synlett 2016; 27(07): 1051-1055
DOI: 10.1055/s-0035-1561199
DOI: 10.1055/s-0035-1561199
cluster
Organocatalysis Intermediates as Platforms to Study Noncovalent Interactions: Integrating Fluorine Gauche Effects in Iminium Systems to Facilitate Acyclic Conformational Control
Further Information
Publication History
Received: 14 December 2015
Accepted: 28 December 2015
Publication Date:
18 January 2016 (online)
◊ X-ray crystallographer
Dedicated to Prof. Dr. Dieter Seebach
Abstract
Achieving acyclic conformational control over several bonds has been realized by the strategic installation of a vicinal difluoroethane bridge in a generic proline-derived organocatalyst. The torsion angle ϕFCCF is governed by stabilizing hyperconjugative interactions (σ→σ*), thus ensuring a 60° relationship. This effect has been telescoped by positioning a stereogenic fluorine center proximal to the nucleophilic amine. Upon iminium formation, this center is rendered electron deficient, thus triggering a dynamic fluorine iminium ion gauche effect. Consequently, conformational control over five atoms and four bonds can be achieved by reversible formation of an iminium π-bond.
Key words
computation - conformational analysis - fluorine - organocatalysis - stereoelectronic effectSupporting Information
- Supporting information for this article is available online at http://dx.doi.org/10.1055/s-0035-1561199.
- Supporting Information
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