Synthesis, Characterizations and Applications of Fluoroazaphosphatranes.

Haloazaphosphatranes are the halogenated parents of proazaphosphatranes, also known as Verkade's superbase. While the synthesis of iodo-, bromo- and chloroazaphosphatranes was reported more than thirty years ago by J. G.

Integrated, one-pot carbon capture and utilisation using porous ionic liquids.

Porous ionic liquids combining alkylphosphonium halides with ZIF-8 absorb large amounts of carbon dioxide that can be catalytically coupled with epoxides to form cyclic carbonates. High activity and selectivity under mild reaction conditions points towards a new promising, high-performing, sustainable family of sorbents for simultaneous carbon capture and transformation.

Enantio- and Substrate-Selective Recognition of Chiral Neurotransmitters with -Symmetric Switchable Receptors.

We report on the synthesis of -symmetric enantiopure cage molecules , which exhibit remarkable to exclusive enantioselective recognition properties toward chiral ammonium neurotransmitters. Strong changes in the substrate selectivity are also observed when different stereoisomers of are used. Furthermore, protonation/deprotonation induces a reversible modification of the conformation of , which switches from an imploded to an inflated form, leading to ejection and reuptake of the guest initially encaged inside the cavity.

Enantiopure encaged Verkade's superbases: Synthesis, chiroptical properties, and use as chiral derivatizing agent.

Verkade's superbases, entrapped in the cavity of enantiopure hemicryptophane cages, have been synthesized with enantiomeric excess (ee) superior to 98%. Their absolute configuration has been determined by using electronic circular dichroism (ECD) spectroscopy. These enantiopure encaged superbases turned out to be efficient chiral derivatizing agents for chiral azides, underlining that the chirality of the cycloveratrylene (CTV) macrocycle induces different magnetic and chemical environments around the phosphazide functions.

Bioinspired Oxidation of Methane in the Confined Spaces of Molecular Cages.

Non-heme iron, vanadium, and copper complexes bearing hemicryptophane cavities were evaluated in the oxidation of methane in water by hydrogen peroxide. According to H nuclear magnetic resonance studies, a hydrophobic hemicryptophane cage accommodates a methane molecule in the proximity of the oxidizing site, leading to an improvement in the efficiency and selectivity for CHOH and CHOOH compared to those of the analogous complexes devoid of a hemicryptophane cage. While copper complexes showed low catalytic efficiency, their vanadium and iron counterparts exhibited higher turnover numbers, ≤13.

Endohedral Functionalized Cage as a Tool to Create Frustrated Lewis Pairs.

A frustrated Lewis pair (FLP) system was obtained by confinement of the Lewis base partner, a Verkade's superbase, in a molecular cavity. Whereas the model superbase lacking cavity displayed no catalytic activity in Morita-Baylis-Hillman (MBH) reactions, when associated to titanium (IV) chloride, the encaged superbase turns out to be an efficient catalyst under the same conditions. The crucial role of the endohedral functionalized cage on catalytic performance was further demonstrated by the fact that model superbases with bulky substituents were much less efficient to produce active catalysts, as well as by inhibition and substrate selection experiments.

Remote control of helical chirality: thermodynamic resolution of a racemic mixture of CTV units by remote stereogenic centers.

Enantiopure hemicryptophanes designed from the cyclotriveratrylene (CTV) unit display remarkable properties in selective host-guest recognition or as supramolecular catalysts. The unprecedented control of the helical chirality of the CTV unit by remote stereogenic centers of a tren moiety is reported, providing an original access to this highly promising class of host molecules. Although the chiral centers and the CTV unit are separated by more than 10 Å, one single diastereomer is formed; the nature of the diastereoselective process is discussed and the procedure is exemplified using different enantiopure tren derivatives.

Catalytic activity of an encaged Verkade's superbase in a base-catalyzed Diels-Alder reaction.

Organocatalysis in a confined space has been performed through encapsulation of a proazaphosphatrane superbase in a hemicryptophane host. The resulting catalyst displays good to high catalytic activity in the base-catalyzed Diels-Alder reactions investigated. A comparison with the model superbase, which lacks a cavity, shows much higher diastereomeric excess with the encaged proazaphosphatrane for the reaction of 3-hydroxy-2-pyrone with N-methylmaleimide.

Azaphosphatrane organocatalysts in confined space: cage effect in CO(2) conversion.

The endohedral functionalization of a molecular cage by an azaphosphatrane unit has allowed for the creation of highly engineered catalytic cavities for efficient conversion of CO2 into cyclic carbonates. Strong structure/activity/stability correlations have been demonstrated by careful adjustment of the size, shape, and electronic properties of the hemicryptophane host.

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.

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.

Shorter and modular synthesis of hemicryptophane-tren derivatives.

Hemicryptophanes are host molecules with many applications as supramolecular catalysts or in ion selective recognition. A very convenient and efficient modular approach for the synthesis of hemicryptophane-tren (tren, tris(2-aminoethyl)-amine) derivatives has been developed. For instance, hemicryptophane 1 was synthesized at the gram scale in four steps from vanillyl alcohol compared to the previous seven-step procedure.

Nanoscale organization of thiol and arylsulfonic acid on silica leads to a highly active and selective bifunctional, heterogeneous catalyst.

Ordered mesoporous silicas functionalized with alkylsulfonic acid and thiol group pairs have been shown to catalyze the synthesis of bisphenols from the condensation of phenol and various ketones, with activity and selectivity highly dependent on the distance between the acid and thiol. Here, a new route to thiol/sulfonic acid paired catalysts is reported. A bis-silane precursor molecule containing both a disulfide and a sulfonate ester bond is grafted onto the surface of ordered mesoporous silica, SBA-15, followed by simultaneous disulfide reduction and sulfonate ester hydrolysis.

Organized surface functional groups: cooperative catalysis via thiol/sulfonic acid pairing.

The synthesis and characterization of heterogeneous catalysts containing surfaces functionalized with discrete pairs of sulfonic acid and thiol groups are reported. A catalyst having acid and thiol groups separated by three carbon atoms is ca. 3 times more active than a material containing randomly distributed acid and thiol groups in the condensation of acetone and phenol to bisphenol A and 14 times more active in the condensation of cyclohexanone and phenol to bisphenol Z.

Design of heterogeneous catalysts via multiple active site positioning in organic-inorganic hybrid materials.

Catalytic materials bearing multiple sulfonic acid functional groups and positioned at varying distances from one another on the surface of mesoporous solids are prepared to explore the effects that the spatial arrangement of active sites have on catalytic activity and selectivity. A series of organosiloxane precursors containing either disulfide or sulfonate ester functionalities (synthons of the eventual sulfonic acid groups) are synthesized. From these molecular precursors, a variety of organic-inorganic hybrid, mesostructured SBA-15 silica materials are prepared using a postsynthetic grafting procedure that leads to disulfide and sulfonate ester modified silicas: [Si]CH(2)CH(2)CH(2)SS-pyridyl, 2.

Catalytic Hydrogenolysis at Low Temperature and Pressure of Polyethylene and Polypropylene to Diesels or Lower Alkanes by a Zirconium Hydride Supported on Silica-Alumina: A Step Toward Polyolefin Degradation by the Microscopic Reverse of Ziegler-Natta Polymerization.

Cleavage and polymerization with the same catalyst: The catalyst system named in the title, which cleaves polyethylene and polypropylene under a hydrogen atmosphere, is also capable of polymerizing ethylene or propylene. This shows the close relationship between olefin insertion and β-alkyl elimination [Eq. (a), (P)=polymer chain(P)].