Three symmetric substances originating from triethyl phosphate were specifically synthesized with varying degree of fluorination at the side chain. Different concentrations of each phosphate were evaluated as co-solvent with regard to their flammability and the electrochemical cycling performance. With higher degree of fluorination and a higher amount of the phosphate in the electrolyte, the self-extinguishing time (SET), a value to determine and compare the flammability of electrolytes, could be significantly lowered to yield a non-flammable electrolyte mixture. A specifically designed SET device is introduced, which offers more accurate results due to lowered standard deviations by minimizing random and systematic errors. As the application of phosphates as co-solvents results in a trade-off in cycling performance, a thorough determination in regard to the ionic conductivity, the anodic oxidation stability and the compatibility with anode and cathode material was carried out in half- and full-cells. The manuscript strives to establish a deeper understanding of the influence that the utilization of phosphates as co-solvents entail with special focus on the fluorination degree. It could be shown that the partially fluorinated phosphate offers the best cycling results and therefore the lowest trade-off in performance, while a severe improvement in SET could be achieved compared to the reference electrolyte.
For almost 40 years, difluoromethylene phosphonates have proven to be versatile molecular tools in biochemical studies owing to their close resemblance to naturally occurring phosphates and phosphonates. As bioisosteric, non‐hydrolyzable analogs of these essential molecules, difluoromethylene phosphonates can target the critical parts of the cellular machinery and therefore exhibit a diverse spectrum of biological activity. In the past ten years, there have appeared many new methods for the synthesis of difluoromethylene phosphonates. Most notably, photoredox catalysis has firmly entered the field, while cross‐coupling and nucleophilic strategies have met considerable elaboration and refinement, entirely in accord with the current trends in synthetic organic chemistry. Herein, we introduce difluoromethylene phosphonates as a distinct, high‐tech subclass of synthetic phosphonates resulting from the research efforts on the cross‐section of organophosphorus, organofluorine, and bioorganic chemistry. We then proceed to the discussion of general methods for the preparation of difluoromethylene phosphonates, comprehensively reviewing reactions developed in the past 15 years while providing the context of earlier works where appropriate. Finally, we present selected examples of molecules with high biological activity, their biological targets, and the synthetic steps employed for their preparation.
Enantiomerically pure N,O-protected b-trifluoromethyl isoserine derivatives of (2S,3S)-and (2R,3S)-absolute configurations have been easily prepared by diastereoselective addition of the enolates, derived from O-protected a-hydroxyacetates, to (S)-N-tert-butanesulfinyl (3,3,3)-trifluoroacetaldimine with high combined yield and good syn/anti stereoselectivity. To explain the unusual stereochemical outcome in these reactions a mechanistic rationale involving the addition of Z-enolates to (S)-imines via open transition states was proposed on the basis of the experimental data. Elaboration of these products via chemoselective manipulation of the protecting groups has been demonstrated.
Four symmetric compounds deriving from the alkyl chain containing tripropyl phosphate were designed and synthesized by varying substitution of fluorine in the side chains and added as co-solvents to yield 10%, 20% and 30% concentrated electrolyte formulations. The formulated electrolytes were physicochemically and electrochemically characterized and compared to a state-of-the-art organic carbonate-based electrolyte in regard to the flammability as well as any occurring trade-off in cycling performance. The addition of phosphates resulted in superior flammability behavior of the electrolyte as the flammability could be severely reduced with increased concentration of the phosphates. As the addition of such phosphate compounds to the electrolyte usually comes with a trade-off in cycling performance, electrochemical behavior was thoroughly investigated regarding ionic conductivity, anodic stability limit and cycling stability in lithium metal and lithium ion cells. The influence of the varying fluorine content as well as position of the substituted fluorine was determined and discussed. The tripropyl phosphate derivatives showed very promising cycling results hand in hand with a significant improvement achieved regarding the flammability of the electrolyte.
α,α-Difluoro-β-ketophosphonated derivatives of tetraazamacrocycles were synthesized and found to be potential inhibitors of protein tyrosine phosphatases. N-Substituted conjugates of cyclam and cyclen with bioisosteric phosphonate groups displayed good activities toward T-cell protein tyrosine phosphatase with IC50 values in the micromolar to nanomolar range and showed selectivity over PTP1B, CD45, SHP2, and PTPβ. Kinetic studies indicated that the inhibitors can occupy the region of the active site of TC-PTP. This study demonstrates a new approach which employs tetraazamacrocycles as a molecular platform for designing inhibitors of protein tyrosine phosphatases.
The Petasis reaction between glyoxylic acid, α amino phosphonates, and organylboronic acid afforded N phosphonomethyl α amino acids. This method has an advantage of prepara tive simplicity and high diastereoselectivity of the reactions. Immunotropic activity of the synthesized compounds was studied using the models in vivo.
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