Synthesis of the First Water-Soluble Hemicryptophane Host: Selective Recognition of Choline in Aqueous Medium

The first water-soluble hemicryptophane cage compound, <b>4</b>, was synthesized in seven steps from commercially available products, and its complexation properties were studied. NMR and ITC experiments indicate that <b>4</b> is an efficient receptor for choline in water (Δ<i>G</i>° = −5.2 kcal mol^–1). High substrate selectivity was achieved since no complexation was observed for its closely related substrates: glycine betaine and betaine aldehyde. Density functional theory calculations were performed to analyze the interactions that are involved in the formation of the inclusion complex

Sulfoxidation inside a <i>C</i>₃‑Vanadium(V) Bowl-Shaped Catalyst

The confined enantiopure oxido-vanadium complex <i>SSS-RRR-</i><b>1</b> was synthesized and tested as a catalyst for the oxidation of sulfides into sulfoxides. This catalyst is very efficient with a reaction rate more than 300 times higher than that of the model compound <i>SSS-RRR-</i><b>3</b>, and a turnover number (TON) close to 10⁵ was reached in combination with a good selectivity (more than 90%) in the sulfoxide product. Moreover, enantiomerically enriched sulfoxide can be obtained, breaking through the major limitation of the previous chiral vanatrane catalysts that show no detectable enantiomeric excess (ee). Further investigations revealed that the complex <i>SSS-RRR-</i><b>1</b> adopts a bowl-shaped structure with an open hydrophobic pocket. The microenvironment of the chiral pocket above the metal center accounts for the strong improvement in catalytic activity and enantioselectivity

Superbases in Confined Space: Control of the Basicity and Reactivity of the Proton Transfer

Endohedral functionalization of the molecular cavity of host molecules is in high demand in many areas of supramolecular chemistry. When highly reactive species are incarcerated in the confined space of a molecular cavity, deep changes of their chemical properties are expected. Here, we show that the superbasic properties of proazaphosphatranes can be improved in the confined space of the molecular cavity of hemicryptophane hosts. A general and modular procedure is described to prepare supramolecular superbases with various cavity sizes. The rate of proton transfer is strongly dependent on the shape and size of the inner cavity of the designed superbasic structure. Kinetic and thermodynamic data are strongly correlated to the space available around the basic center as revealed by the X-ray molecular structures analyses

Superbases in Confined Space: Control of the Basicity and Reactivity of the Proton Transfer

Endohedral functionalization of the molecular cavity of host molecules is in high demand in many areas of supramolecular chemistry. When highly reactive species are incarcerated in the confined space of a molecular cavity, deep changes of their chemical properties are expected. Here, we show that the superbasic properties of proazaphosphatranes can be improved in the confined space of the molecular cavity of hemicryptophane hosts. A general and modular procedure is described to prepare supramolecular superbases with various cavity sizes. The rate of proton transfer is strongly dependent on the shape and size of the inner cavity of the designed superbasic structure. Kinetic and thermodynamic data are strongly correlated to the space available around the basic center as revealed by the X-ray molecular structures analyses

Superbases in Confined Space: Control of the Basicity and Reactivity of the Proton Transfer

Endohedral functionalization of the molecular cavity of host molecules is in high demand in many areas of supramolecular chemistry. When highly reactive species are incarcerated in the confined space of a molecular cavity, deep changes of their chemical properties are expected. Here, we show that the superbasic properties of proazaphosphatranes can be improved in the confined space of the molecular cavity of hemicryptophane hosts. A general and modular procedure is described to prepare supramolecular superbases with various cavity sizes. The rate of proton transfer is strongly dependent on the shape and size of the inner cavity of the designed superbasic structure. Kinetic and thermodynamic data are strongly correlated to the space available around the basic center as revealed by the X-ray molecular structures analyses

Azaphosphatranes as Structurally Tunable Organocatalysts for Carbonate Synthesis from CO₂ and Epoxides

Three azaphosphatranes were used as organocatalysts for the synthesis of cyclic carbonates from CO₂ and epoxides. They proved to be efficient single-component, metal-free catalysts for the reaction of simple or activated epoxides (styrene oxide, epichlorohydrin, glycidyl methyl ether) with CO₂ under mild reaction conditions, displaying high stability and productivity over several days of reaction. Substitution patterns on the catalyst were shown to affect activity and stability. Kinetic analysis allowed investigation of the reaction mechanism

Cyclotriveratrylene-BINOL-Based Host Compounds: Synthesis, Absolute Configuration Assignment, and Recognition Properties

New host compounds combining a cyclotriveratrylene (CTV) unit and three binaphthol moieties have been synthesized enantiomerically and diastereomerically pure. The use of a chemical correlation allows for the assignment of their absolute configuration. The energy barrier of epimerization was measured, suggesting that no intramolecular hydrogen bonding occurs between the hydroxyl groups of the binaphthols. These open-shell host compounds were then tested in the recognition of carbohydrates; a preferential binding of mannose toward glucose was observed, and good diastereoselectivities were reached (up to 1:10). This recognition of sugar derivatives by open-shell CTV-based host compounds is unprecedented and opens up the way for a wider use of this easily accessible class of molecules as chiral sensors

Straightforward Access to Chiral Phosphangulene Derivatives

Polycyclic aromatic hydrocarbons including heteroatoms have found a wide range of applications, for instance, in supramolecular chemistry or material science. Phosphangulene derivatives are P-containing polycyclic aromatic hydrocarbons presenting a concave aromatic surface suitable for building supramolecular receptors. However, the applications of this convenient building block have been strongly hampered by a difficult and multistep preparation requiring several protection–deprotection sequences along with the use of harmful reagents. Here, we report a straightforward, protecting-group-free, three-step, and hundred-milligram-scale synthesis of a chiral phosphangulene oxide derivative via a triple phospho-Fries rearrangement. This compound was easily resolved by chiral HPLC and further functionalized, giving rise to versatile chiral phosphangulene derivatives. Following this strategy, chiral phosphangulene oxides with low symmetry were synthesized. Molecular crystal structures revealed a variety of molecular organization in the solid. This opens the way to wider use of this compound as a building block for cages or new materials