Robby Vroemans

Synlett
DOI: 10.1055/a-2377-0629

In recent years, there have been increasing efforts in the development of methodologies for incorporating fluorine-containing functional groups into organic scaffolds. Modern techniques have made fluorinated molecules more accessible than ever before, but many fluorination reactions still have limitations in their generality, predictability, sustainability, and cost-effectiveness. The methodological progress has a significant impact on drug discovery and materials science research. Photoredox catalysis has enabled the discovery of effective methods, providing access to druglike molecules. Photochemical methods paired with C–H functionalization provide powerful tools for property-driven research. Herein, we examine recent developments at the interface of photoredox catalysis and C–H functionalization.1 Introduction2 Fluorinations3 Fluoroalkylations4 Fluoroalkoxylations5 Conclusion
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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A scalable method was developed to convert lignin-based aromatic acids into methacrylate monomers. Subsequently, polymethacrylates with glass transition temperatures close to 200 °C were prepared by radical polymerization. Life cycle and toxicity evaluation showed results competitive with fossil-based methyl methacrylate.

Abstract

There is currently a great need for rigid, high-performance and processable bio-based polymers and plastics as alternatives to the fossil-based materials used today. Here, we report on the straightforward synthesis and polymerization of lignin-derived methacrylate monomers based on the methyl esters of 4-hydroxybenzoic, vanillic, and syringic acid, respectively. The corresponding homopolymethacrylates exhibit high glass transition temperatures (T _gs) at 106, 128, and 197 °C, respectively. Rheological properties and thermal stability up to at least 277 °C indicate that these polymers are melt-processable. In addition, copolymers with methyl methacrylate are prepared to further vary and tune the polymer properties. An integrated ex-ante and prospective life-cycle assessment of key environmental impact parameters indicates similar or only slightly higher values compared to well-established fossil-based methyl methacrylate. Moreover, the toxicity towards human HeLa cell lines compares well with that of poly(methyl methacrylate). Hence, the potential availability of lignin-derived acids, combined with the straightforward and potentially upscalable monomer synthesis, make these rigid polymers appealing alternatives towards bio-based high-T _g thermoplastic materials with low toxicity.

Synlett
DOI: 10.1055/s-0043-1775397

Aging alcohol is a timeless process that has seen little variation since the time of its invention. Molecules stored within the wood can be extracted by the alcohol to produce unique flavors. Among these molecules exist the whiskey and cognac lactones. Herein we report a short synthesis of the trans-whiskey and cognac lactones using a rearrangement of cyclopropane hemimalonates.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Polymers with covalently incorporated donor-acceptor torsional springs allow for real-time monitoring of forces, that are calibrated using known spiropyran mechanophores. This concept is demonstrated using glassy, entangled polymers and elastomeric networks.

Abstract

Sterically distorted donor-acceptor π-systems, termed DA springs, can be progressively planarized under mechanical load causing a bathochromic shift of the photoluminescence (PL) spectrum. By combining theory and experiment, we here use a simple linear force calibration for two different conformational mechanochromophores to determine molecular forces in polymers from the mechanochromic shift in PL wavelength during multiple uniaxial tensile tests. Two systems are used, i) a highly entangled linear glassy polyphenylene and ii) a covalent elastomeric polydimethylsiloxane network. The mean forces estimated by this method are validated using known threshold forces for the mechanochemical ring-opening reactions of two different spiropyran force probes. The agreement between both approaches underlines that these DA springs provide the unique opportunity for the online monitoring of local molecular forces present in diverse polymer matrices.

Co₄Ni₆@Cu and Fe₃Ni₇@Cu nanoparticles containing a magnetic core and a catalytic shell have been synthesized and found to be highly active catalysts for amination of primary and secondary alcohols with secondary amines when an alternating magnetic field (AMF) is applied. Several tertiary amines have hence been prepared under argon without hydrogen feed. This process allows to limit degradation reactions of the reagents and of the products and can therefore be used for the synthesis of other thermally sensitive molecules.

Abstract

The synthesis of tertiary amines from alcohols (i.e. heptanol, dodecanol, cyclohexanol, benzylalcohol) and secondary amines (Me₂NH (DMA), ⁿPr₂NH, ⁿBu₂NH) has been achieved in one step using trimetallic nanoparticles (NPs) displaying a magnetic core (Co₄Ni₆ and Fe₃Ni₇) and a Cu shell as both catalysts and heating agent in the presence of an alternating magnetic field. This methodology limits the redistribution reactions occurring on amines at high temperature leading to both much higher conversion and selectivity in the absence of solvent than usually observed using conventional heating. Moreover, Co₄Ni₆@Cu NPs were found moisture resistant, thereby allowing for performing the reaction with commercial DMA in water (40 % wt) with again high conversion and selectivity.

A visible-light-induced, efficient one-pot synthesis of β-hydroxysulfides from olefins, thiosulfonates, and HCOOCs, utilizing an EDA complex strategy under ambient air conditions at room temperature, has been successfully developed. This approach offers mild reaction conditions, simplicity, odorlessness, and remarkable functional group tolerance.

Comprehensive Summary

A visible-light-induced and efficient one-pot synthesis of β-hydroxysulfides from olefins, thiosulfonates and HCOOCs using an EDA complex strategy under air atmosphere at room temperature has been disclosed. A plausible radical involved mechanism is proposed. During the reaction process, formates play a crucial role: first, as donors in the EDA complex; second, as providers of the hydrogen source; and third, by generating CO₂ ^•– to reduce peroxide intermediates, leading to the formation of β-hydroxysulfides. In contrast to the previously reported thiol-oxygen co-oxidation reactions, this simple and sustainable approach features mild reaction conditions, operational simplicity, odorless and excellent functional group tolerance.

Nature Chemistry, Published online: 15 August 2024; doi:10.1038/s41557-024-01612-y

The development of enantiospecific sulfone reactions has been hindered by the inherent acidity of sulfones, which result in deleterious racemization. Now, the synthesis of enantioenriched diarylalkanes has been reported via sufficiently fast cross-coupling that circumvents racemization of the chiral sulfone.

Synlett
DOI: 10.1055/s-0043-1775380

Ketocalix[n]arenes can be prepared via oxidation of the methylene groups of protected calix[n]arenes. The presence of carbonyl groups at the bridges alters the preferred conformation and reactivity of the macrocycle and provides an entry point (via nucleophilic additions reactions) to a wide array of methylene-substituted derivatives as well as calix[n]radialenes.1 Introduction2 Synthesis of Ketocalix[n]arenes2.1 Ketocalix[4]arene Derivatives2.2 Systems Possessing both Carbonyl and Bromomethane Bridges2.3 Pentaoxoketocalix[5]arene and Hexaoxoketocalix[6]arene Derivatives2.4 Monooxo- and Dioxoketocalix[6]arenes3 Conformation of Ketocalixarenes4 Reactions of Ketocalixarenes4.1 Alkylation of the OH Groups4.2 Intramolecular Aromatic Nucleophilic Substitution4.3 Reduction of the Carbonyl Groups4.4 Reaction of 5c with PhLi4.5 Reaction with tert-Butyllithium5 From Ketocalix[n]arenes to Calix[n]radialenes and Calix[n]rotanes6 Summary and Outlook
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Scientists are struggling to figure out why—and how—the standard growth medium is disrupting their studies