Fluor in einer C‐F‐Bindung als Schlüssel für die Käfigbildung

We report the first spectroscopic evidence for a [C−F−C]+ fluoronium ion in solution. Extensive NMR studies (19F, 1H, 13C) characterize a symmetric cage‐like species in which fluorine exhibits substantial covalent bonding to each of the two carbon atoms involved in the three‐center interaction. Experimental NMR data comport well with calculated values to lend credence to the structural assignment. As the culminating experiment, a Saunders isotopic perturbation test confirmed the symmetric structure. Congruent with the trend in other types of onium ions, the calculated charge at fluorine moves in a more positive (less negative) direction from the neutral. It is this important trend that explains in part the extraordinary historical difficulty in making theoretical predictions of fluoronium ions come true in solution, and why it takes fluorine captured in a cage to produce, finally, a stable ion and complete the historical arc of the organic halonium ion story.

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Spectroscopic Characterization of a [C−F−C]⁺ Fluoronium Ion in Solution

Pitts

Holl

Lectka

2018

Angewandte Chemie

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Enantioselective Electrophilic Aromatic Nitration: A Chiral Auxiliary Approach

et al. 2018

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Enantioselective electrophilic aromatic nitration methodology is needed to advance chirality‐assisted synthesis (CAS). Reported here is an enantioselective aromatic nitration strategy operating with chiral diester auxiliaries, and it provides an enantioselective synthesis of a C3v‐symmetric tribenzotriquinacene (TBTQ). These axially‐chiral structures are much sought‐after building blocks for CAS, but they were not accessible prior to this work in enantioenriched form without resolution of enantiomers. This nitration strategy controls the stereochemistry of threefold nitration reactions from above the aromatic rings with chiral diester arms. Dicarbonyl‐to‐arenium chelation rigidifies the reaction systems, so that remote stereocenters position the ester‐directing groups selectively over specific atoms of the TBTQ framework. Closely guided by computational design, a more selective through‐space directing arm was first predicted with density functional theory (DFT), and then confirmed in the laboratory, to outperform the initial structural design. This enantio‐ and regioselective TBTQ synthesis opens a new pathway to access building blocks for CAS.

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Solid‐State Radical C−H Trifluoromethylation Reactions Using Ball Milling and Piezoelectric Materials

et al. 2020

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The application of piezoelectricity for the generation of trifluoromethyl (CF3) radicals is reported together with the development of a method for the mechanochemical C−H trifluoromethylation of aromatic compounds. As compared to conventional solution‐based approaches, this mechanoredox C−H trifluoromethylation enables cleaner and more sustainable access to a wide range of trifluoromethylated N‐heterocycles and peptides, which are important structural motifs in modern drug discovery. This study thus represents an important milestone for future applications of mechanoredox systems to medicinal and pharmaceutical science.

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Fluor in einer C‐F‐Bindung als Schlüssel für die Käfigbildung

Abstract: This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record.

Cited by 10 publications

References 53 publications

Spectroscopic Characterization of a [C−F−C]⁺ Fluoronium Ion in Solution

Spectroscopic Characterization of a [C−F−C]⁺ Fluoronium Ion in Solution

Enantioselective Electrophilic Aromatic Nitration: A Chiral Auxiliary Approach

Solid‐State Radical C−H Trifluoromethylation Reactions Using Ball Milling and Piezoelectric Materials

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Fluor in einer C‐F‐Bindung als Schlüssel für die Käfigbildung

Abstract: This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record.

Cited by 10 publications

References 53 publications

Spectroscopic Characterization of a [C−F−C]+ Fluoronium Ion in Solution

Spectroscopic Characterization of a [C−F−C]+ Fluoronium Ion in Solution

Enantioselective Electrophilic Aromatic Nitration: A Chiral Auxiliary Approach

Solid‐State Radical C−H Trifluoromethylation Reactions Using Ball Milling and Piezoelectric Materials

Contact Info

Product

Resources

About

Spectroscopic Characterization of a [C−F−C]⁺ Fluoronium Ion in Solution

Spectroscopic Characterization of a [C−F−C]⁺ Fluoronium Ion in Solution