Studies on selectively fluorinated cycloalkanes

The thesis focuses on the synthesis of novel fluorinated cycloalkanes and their polar properties. Chapter 2 describes the synthesis of all cis-1,2,3,4-tetrafluorocyclopentane and its deuterated isotopomer. They were prepared from the dicyclopentadiene. The structure of cis-1,2,3,4-tetrafluorocyclopentane was characterised by NMR and X-ray crystallography. This structure proved to have high polarity and a calculated dipole moment is 4.9 Debye. The deuterated isotopomer was also characterised by NMR and it indicated that this molecule has highly polarized faces similar to all cis-1,2,3,4-tetrafluorocyclopentane. The polarity of the isotopomers were compared by GC-MS analysis and this gave an indication that per-deuterated isotopomer is more polar than the all cis-1,2,3,4-tetrafluorocyclopentane. Chapter 3 describes the synthesis of a series of fluorinated cyclopropanes, with a particular focus on the preparation of the all cis-1,2,3-trifluorocyclopropane motif. The synthesis started from the fluorinated styrene, followed by bromofluocarbene (:CFBr) addition and reductive debromination. This provided the first synthetic access to this motif. The lipophilicity (Log P) of a series of fluorinated cyclopropanes was investigated and the results demonstrated that the all cis-1,2,3-trifluorocyclopropane was the most polar compound among this series. Chapter 4 describes unexpected results from the fluorination of benzo[a,e]cyclooctatetraene with NBS, HF·Py and AgF(I), which was anticipated to generate all-cis-5,6,11,12-tetrafluoro-5,6,11,12-tetrahydrodibenzo[a,e]cyclooctane. However, the reaction gave a mixture of products and the product outcomes strongly suggests that an extensive carbocation/phenonium rearrangements pathway occurred during the reaction. The origin of oxygen in the final ether products was shown by an 18O isotope labelling experiment with water and the result suggests a {Ag}O- species is the most likely oxygen provider. Chapter 5 describes the synthesis of a series of novel liquid crystals with fluorinated cyclopropane motifs at their terminus. The synthesis proved straightforward such that these novel liquid crystal candidates can be prepared on scale. Their thermodynamic and physical properties, such as birefringence (Δn), dielectric anisotropy (Δε) and rotational viscosity (ϒ) were analysed by Merck & Co. Although none of the liquid crystal candidates met all the criteria for Liquid Crystal Display (LCD) development, the study gives an insight into the potential for fluorinated cyclopropane motifs in liquid crystals."I gratefully acknowledge the EPSRC for funding (GR: EP/R013799/1) and the China Scholarship Council for PhD studentship support." -- Acknowledgement

Does perdeuteration increase the polarity of Janus face cycloalkanes?

Funding: Authors are grateful to the Chinese Scholarship Council for studentship (Z. F. and C. Y.) support and also the Scientific Research Project of Hubei Education Department (Q20211402) and the open project of Hubei Provincial Key Laboratory of Green Materials for Light Industry (202107B06) for financial support.Stimulated by a suggestion of the late Professor Jack D. Dunitz, that perdeuterated Janus face cycloalkanes may be more polar than their unlabelled forms, the deuterated isotopologue of all cis-1,2,3,4,5,6-hexafluorocyclohexane ([2H6]- 1a ) and all cis-1,2,3,4-tetrafluorocyclopentane ([2H6]- 3a ) were prepared. Computation at the B3LYP−D3 level indicated that [2H6]- 1a is not more polar than its protio form 1, however perdeuterated cyclopentane [2H6]- 3a may indeed be more polar than 3 , although the magnitude is predicted to be small. None-the-less retention time analysis on a reverse phase GC/MS column of an add-mix of 3 and [2H6]- 3a gave some indication that the per-deuterated isotopologue 3a was detected marginally before the unlabelled compound consistent with increased polarity associated with perdeuteration.Publisher PDFPeer reviewe

Fluorine containing cyclopropanes : synthesis of aryl substituted all-cis 1,2,3-trifluorocylopropanes, a facially polar motif

We thank the EPSRC for financial support (GR: EP/R013799/1) and we are grateful to the Chinese Scholarship Council (CSC) for Ph.D Studentship support (ZF).The synthesis of substituted all-cis-1,2,3-trifluorocylopropanes are described for the first time. The three fluorines located on each of the cyclopropyl carbons with a stereochemistry where they are all on the same face of the cyclopropane, imparts a significant polarity to the molecule, and the inherent conformational rigidity and lowering of Log P makes this motif attractive for exploration as a substituent for pharmaceuticals and agrochemicals research.PostprintPeer reviewe

Polar alicyclic rings: synthesis and structure of all cis-1,2,3,4-tetrafluorocyclopentane

The authors are grateful to the Chinese Scholarship Council for Studentship support (ZF), to EPSRC for financial support and to the EPSRC National Mass Spectrometry Service at Swansea for analytical support. DO’H thanks the Royal Society for a Wolfson Research Merit Award.The all-cis isomer of 1,2,3,4-tetrafluorocyclopentane is prepared and characterised by NMR and X-ray crystallography and the experimental structure compared with theory. The structure has a similarly high polarity to all-cis tetrafluorocyclohexanes despite the increased conformational flexibility of a cyclopentane.PostprintPeer reviewe

Synthesis of organic liquid crystal containing selectively fluorinated cyclopropanes

Authors thank the Chinese Scholarship Council for a studentship (ZF) and the EPSRC Mass Spectroscopy Service at Swansea for analysis.This paper describes the synthesis of a series of organic liquid crystals (LC) containing selectively fluorinated cyclopropanes at their termini. The syntheses used difluorocarbene additions to olefin precursors, an approach which proved straightforward such that these liquid crystal candidates could be efficiently prepared. Their physical and thermodynamic properties were evaluated and depending on individual structures, they either displayed positive or negative dielectric anisotropy. The study gives some guidance into effective structure property relationships for the design of LCs containing selectively fluorinated cyclopropane motifs.Publisher PDFPeer reviewe

Evolution of Anodic Product from Molybdenum Metal in Absolute Ethanol and Humidity Sensing under Ambient Conditions

Authors would like to thank the support from National Natural Science Foundation of China (NSFC) (Nos. 51702264 and 41371275), Fundamental Research Funds for the Central Universities (No. XDJK2017B033), and Research Funding of Southwest University (No. SWU117019). The funding from the Engineering and Physical Sciences Research Council (EPSRC) (under Grant Nos. EP/K022237/1, EP/K036769/1, and EP/M024938/1) is also acknowledged. We also appreciate the funding from the EU COST Action (No. TD1208) for useful exchanges and discussions.Room-temperature nonaqueous synthetic routes turn out to be particularly competitive among all the available liquid-phase synthetic methods for nanometer-sized metal oxides for multiple applications. Microplasma-assisted anodization is employed to prepare soluble and crystalline Mo species in a water-deficient and extraneous ionic-salt-free ethanol electrolyte. The anodization of Mo in absolute ethanol is found to produce Mo oxyethoxide in the liquid ethanol phase, along with a small montage of mixed hexagonal and orthorhombic MoO3 crystals. The evolution of Mo species in solid and liquid phases is characterized to study the crystallization of MoO3 crystal and the formation of blue spherical Mo polyoxometalates (POMs) after extended aging. The addition of water in the suspension delayed the formation of molybdenum blue while hydrogen peroxide induced the precipitation of a dendritic framework of hexagonal MoO3. A thin MoO3 film was produced from the solution and can be used for humidity sensing by the facile conductivity measurement.PostprintPostprintPeer reviewe

Microplasma-assisted electrochemical synthesis of Co3O4 nanoparticles in absolute ethanol for energy applications

The authors thank the Engineering and Physical Sciences Research Council (EPSRC) for funding (EP/K036769/1, EP/K022237/1, EP/M024938/1). The authors would also like to acknowledge the EU COST Action TD1208 for useful exchanges and discussions. CN would like to thank the support from Fundamental Research Funds for the Central Universities (XDJK2017B033) and Research Funding of Southwest University (SWU117019) and Natural Science Foundation of China (NSFC, 51702264; 41371275).Plasma at the gas/liquid interface can promote a complex mixture of reactions in solution and microplasma-assisted direct-current anodic oxidation is an efficient and green process in synthesising nanoscale materials for various applications. In this study, we demonstrated the direct synthesis of crystalline Co3O4 quantum dots, ca. 2-5 nm in size, by direct anodization of Co foil with charge balanced by the microplasma at the flowing-helium/pure-ethanol interface under ambient condition. The anodic oxidation of cobalt in ethanol was analysed after characterising the solution using nuclear magnetic resonance (NMR), light absorption, photoluminescence (PL), and the solid product using X-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Using the microplasma with high voltage under ambient condition, ethanol was oxidised to acetate as the charge carrier and the size of Co3O4 quantum dots can be controlled by the limiting current. The quantum dots from this method are well dispersed in ethanol and a dense coating for light absorption and a rectified diode can be processed directly from the suspension. These results reveals that microplasma-assisted anodisation in ethanol is an efficient and green route capable of manufacturing quantum dots at low-temperature and avoiding the use of extraneous ionic salts in electrolyte.PostprintPeer reviewe

Fluorine containing cyclopropanes:synthesis of aryl substituted all-<i>cis </i>1,2,3-trifluorocylopropanes, a facially polar motif

The synthesis of substituted all-cis-1,2,3-trifluorocylopropanes are described for the first time. The three fluorines located on each of the cyclopropyl carbons with a stereochemistry where they are all on the same face of the cyclopropane, imparts a significant polarity to the molecule, and the inherent conformational rigidity and lowering of Log P makes this motif attractive for exploration as a substituent for pharmaceuticals and agrochemicals research

Unexpected α,α'-difluoroethers from Ag(i)F and N-bromosuccinimide reactions of dibenzo[a,e]cyclooctatetraene

An unexpected and highly efficient reaction of dibenzo[a,e]cyclooctatetraene with Ag(I)F and N-bromosuccinamide in dichloromethane results in a sequential ring contraction pathway to generate bridged bicyclic α,α′-difluoroether isomers 10 and 11 where the ether oxygen is isotopically labelled from oxygen-18 water. In diethyl ether the same reaction generates the more classical vicinal difluoride isomers 13 and 14.</p

CCDC 1981334: Experimental Crystal Structure Determination

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