Wittig olefination “baking powder”: a hexameric halogen-bonded phosphonium salt cage for encapsulation and mechanochemical transformation of small-molecule carbonyl compounds

We report a hexameric supramolecular cage assembled from the components of a Wittig-type phosphonium salt, held together by charge-assisted R-Br· · ·Br-· · ·Br-R halogen bonds. The cage reliably encapsulates small polar molecules, including aldehydes and ketones, to provide host-guest systems in which components are pre-formulated in a near-ideal stoichiometry for a base-activated Wittig olefination in the solid-state. These pre-formulated solids enable a molecular-level “baking powder” approach for solvent-free Wittig reactions, based on a design of solid-state reactivity in which the host for molecular inclusion also acts as a complementary reagent for the chemical transformation of an array of guests. These host-guest solid-state complexes can also act as supramolecular surrogates to their Wittig olefination vinylbromide products, in a Sonogashira-type coupling that enables one-pot mechanochemical conversion of an aldehyde to an enediyne.

Mechanochemical transformation of planar polyarenes to curved fused-ring systems

The transformation of planar aromatic molecules into π-extended non-planar structures is a challenging task and has not been realized by mechanochemistry before. Here we report that mechanochemical forces can successfully transform a planar polyarene into a curved geometry by creating new C-C bonds along the rim of the molecular structure. In doing so, mechanochemistry does not require inert conditions or organic solvents and provide better yields within shorter reaction times. This is illustrated in a 20-minute synthesis of corannulene, a fragment of fullerene C60, in 66% yield through ball milling of planar tetrabromomethylfluoranthene precursor under ambient conditions. Traditional solution and gas-phase synthetic pathways do not compete with the practicality and efficiency offered by the mechanochemical synthesis, which now opens up a new reaction space for inducing curvature at a molecular level.

Mechanochemical Transformation of Planar Polyarene to Curved Fused-Ring System: Solid-Phase Synthesis of Corannulene

This work demonstrates that mechanochemical forces can successfully transform a planar<br>polyarene into a curved geometry by creating new C-C bonds along the rim of the molecular structure.<br>In doing so, mechanochemistry does not require inert conditions or organic solvents and provide<br>better yields within shorter reaction times. This is illustrated in a 15-minute synthesis of corannulene,<br>a fragment of fullerene C60, in 66% yield through ball milling of planar tetrabromomethylfluoranthene<br>precursor under ambient conditions. Traditional solution and gas-phase synthetic pathways do not<br>compete with the practicality and efficiency offered by the mechanochemical synthesis, which now<br>opens up a new reaction space for inducing curvature at a molecular level.

Mechanochemical Transformation of Planar Polyarene to Curved Fused-Ring System: Solid-Phase Synthesis of Corannulene

This work demonstrates that mechanochemical forces can successfully transform a planar<br>polyarene into a curved geometry by creating new C-C bonds along the rim of the molecular structure.<br>In doing so, mechanochemistry does not require inert conditions or organic solvents and provide<br>better yields within shorter reaction times. This is illustrated in a 15-minute synthesis of corannulene,<br>a fragment of fullerene C60, in 66% yield through ball milling of planar tetrabromomethylfluoranthene<br>precursor under ambient conditions. Traditional solution and gas-phase synthetic pathways do not<br>compete with the practicality and efficiency offered by the mechanochemical synthesis, which now<br>opens up a new reaction space for inducing curvature at a molecular level.

The Activation Efficiency of Mechanophores Can Be Modulated by Adjacent Polymer Composition

<div> <div> <div> <p>The activation efficiency of mechanophores in stress-responsive polymers is generally limited by the competing process of unspecific scission in other parts of the polymer chain. Here it is shown that the linker between the mechanophore and the polymer backbone determines the force needed to activate the mechanophore. Using quantum chemical methods, it is demonstrated that the activation forces of three mechanophores (Dewar benzene, benzocyclobutene and gem-dichlorocyclopropane) can be adjusted over a range of almost 300% by modifying the chemical composition of the linker. The results are discussed in terms of changes in electron density, strain distribution and structural parameters during the rupture process. Using these findings it is straightforward to either significantly enhance or reduce the activation rate of mechanophores in stress-responsive materials, depending on the desired use case. The methodology is applied to switch a one-step “gating” of a mechanochemical transformation to a two-step process. </p> </div> </div> </div>

The Activation Efficiency of Mechanophores Can Be Modulated by Adjacent Polymer Composition

<div> <div> <div> <p>The activation efficiency of mechanophores in stress-responsive polymers is generally limited by the competing process of unspecific scission in other parts of the polymer chain. Here it is shown that the linker between the mechanophore and the polymer backbone determines the force needed to activate the mechanophore. Using quantum chemical methods, it is demonstrated that the activation forces of three mechanophores (Dewar benzene, benzocyclobutene and gem-dichlorocyclopropane) can be adjusted over a range of almost 300% by modifying the chemical composition of the linker. The results are discussed in terms of changes in electron density, strain distribution and structural parameters during the rupture process. Using these findings it is straightforward to either significantly enhance or reduce the activation rate of mechanophores in stress-responsive materials, depending on the desired use case. The methodology is applied to switch a one-step “gating” of a mechanochemical transformation to a two-step process. </p> </div> </div> </div>

Pasteur made simple – mechanochemical transformation of racemic amino acid crystals into racemic conglomerate crystals

Racemic compounds of proteinogenic amino acids valine, leucine and isoleucine were transformed to their corresponding conglomerates via a metal-mediated mechanochemical process.

Mechanical Transformation of Compounds Leading to Physical, Chemical, and Biological Changes in Pharmaceutical Substances

This study demonstrates the link between the modification of the solid-phase pharmaceutical substances mechanical structure and their activity in waters with different molar ratio «deuterium-protium». Mechanochemical transformation of the powders of lactose monohydrate and sodium chloride as models of nutrients and components of dosage forms was investigated by the complex of physicochemical and biological methods. The solubility and kinetic activity of substances dispersed in various ways showed a positive correlation with the solvent isotope profile. Substances dissolved in heavy water were more active than solutes in natural water. Differential IR spectroscopy confirmed the modification of substituents in the sample of lactose monohydrate, demonstrating physicochemical changes during mechanical intervention. The biological activity of the compounds was determined by the method of Spirotox. The activation energy was determined by Arrhenius. Compared with the native compound, dispersed lactose monohydrate showed lower activation energy and, therefore, greater efficiency. In conclusion, proposed data confirm the statement that mechanical changes in compounds can lead to physicochemical changes that affect chemical and biological profiles.