Synlett 2016; 27(07): 1051-1055
DOI: 10.1055/s-0035-1561199
cluster
© Georg Thieme Verlag Stuttgart · New York

Organocatalysis Intermediates as Platforms to Study Noncovalent Interactions: Integrating Fluorine Gauche Effects in Iminium Systems to Facilitate Acyclic Conformational Control

István Gábor Molnár
a   Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany, Email: ryan.gilmour@uni-muenster.de
,
Mareike C. Holland
a   Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany, Email: ryan.gilmour@uni-muenster.de
b   Department of Chemistry and Biochemistry, University of California Los Angeles, 607 Charles E. Young Drive East, Los Angeles, CA 90095-1569, USA
,
Constantin Daniliuc
a   Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany, Email: ryan.gilmour@uni-muenster.de
,
K. N. Houk
b   Department of Chemistry and Biochemistry, University of California Los Angeles, 607 Charles E. Young Drive East, Los Angeles, CA 90095-1569, USA
,
Ryan Gilmour*
a   Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany, Email: ryan.gilmour@uni-muenster.de
c   Excellence Cluster EXC 1003, Cells in Motion, Westfälische Wilhelms-Universität Münster, Waldeyerstrasse 15, 48149 Münster, Germany   Email: ryan.gilmour@uni-muenster.de
› Author Affiliations
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.

Supporting Information

 
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