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A new hemicryptophane host with a ditopic molecular cavity combining a cyclotriveratrylene (CTV) unit with a tris‐urea moiety was synthesized. The complexation of halides, tetramethylammonium (TMA+) cation, and ion pairs was investigated. A positive cooperativity was observed, since halides display a higher binding constant when a TMA+ cation is already present inside the cage. When TMA+ was complexed alone, a decrease of temperature from 298 K to 230 K was required to switch from a fast to a slow exchange regime on the NMR time scale. Nevertheless, the prior complexation of a halide guest in the lower part of the host resulted in significant decrease of the exchange rate of the subsequent complexation of the TMA+ cation. Under these conditions, the 1H NMR signals characteristic of a slow exchange regime were observed at 298 K. Addition of an excess of salts, increases the ionic strength of the solution, restoring the fast exchange dynamics. This result provides insight on how the exchange rate of a cation guest can be modulated by the complexation of a co‐guest anion. [ABSTRACT FROM AUTHOR]

The persistent organic pollutant chlordecone massively contaminates water resources of the French West Indies. Hemicryptophanes are cages capable of complexing chlordecone in organic solvents. Here we demonstrate that a hemicryptophane cage is not only able to recognize this pollutant in chloroform but is also efficient for the removal of chlordecone from water. This evidences that, beyond our previously reported proof of concept, this receptor could be apply as a direct and efficient depolluting agent, making it a promising system for applied supramolecular chemistry. A simple pH switch (basic washing) enables the release of chlordecone from the host, under its deprotonated form, allowing the empty supramolecular cage to be recycled and reused. This method for recycling the receptor, is to the best of our knowledge unprecedented. [ABSTRACT FROM AUTHOR]

The design of molecular cages with low symmetry could allow for more specific tuning of their properties and better mimic the unsymmetrical and complex environment of protein pockets. However, the added value of lowering symmetry of molecular receptors has been rarely demonstrated. Herein, C3‐ and C1‐symmetrical cages, presenting the same recognition sites, have been synthesized and investigated as hosts for carbohydrate recognition. Structurally related derivatives of glucose, galactose and mannose were found to have greater affinity to the receptor with the lowest symmetry than to their C3‐symmetrical analogue. According to the host cavity modelling, the C1 symmetry receptor exhibits a wider opening than its C3‐symmetrical counterpart, providing easier access and thus promoting guest proximity to binding sites. Moreover, our results show the high stereo‐ and substrate selectivity of the C1 symmetry cage with respect to its C3 counterpart in the recognition of sugars. [ABSTRACT FROM AUTHOR]

Recently, porous organic crystals (POC) based on macrocycles have shown exceptional sorption and separation properties. Yet, the impact of guest presence inside a macrocycle prior to adsorption has not been studied. Here we show that the inclusion of trimethoxybenzyl‐azaphosphatrane in the macrocycle cucurbit[8]uril (CB[8]) affords molecular porous host⋅guest crystals (PHGC‐1) with radically new properties. Unactivated hydrated PHGC‐1 adsorbed iodine spontaneously and selectively at room temperature and atmospheric pressure. The absence of (i) heat for material synthesis, (ii) moisture sensitivity, and (iii) energy‐intensive steps for pore activation are attractive attributes for decreasing the energy costs. 1H NMR and DOSY were instrumental for monitoring the H2O/I2 exchange. PHGC‐1 crystals are non‐centrosymmetric and I2‐doped crystals showed markedly different second harmonic generation (SHG), which suggests that iodine doping could be used to modulate the non‐linear optical properties of porous organic crystals. [ABSTRACT FROM AUTHOR]

The globular and monocationic guest molecule trimethyl‐azaphosphatrane (AZAP, a protonated Verkade superbase) was shown to form a host:guest 1 : 1 complex with the cucurbit[10]uril (CB[10]) macrocycle in water. Molecular dynamics calculations showed that CB[10] adopts an 8‐shape with AZAP occupying the majority of the internal space, CB[10] contracting around AZAP and leaving a significant part of the cavity unoccupied. This residual space was used to co‐include planar and monocationic co‐guest (CG) molecules, affording heteroternary CB[10]⋅AZAP⋅CG complexes potentially opening new perspectives in supramolecular chemistry. [ABSTRACT FROM AUTHOR]

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. Verkade, the first synthesis of fluoroazaphosphatranes was only described in 2018 by Stephan et al. Currently, no common and versatile procedure exists to access fluoroazaphosphatranes platform with different structural characteristics. In this report, a new and simple synthesis of this class of compounds was developed based on the nucleophilic attack of the fluoride anion on chloroazaphosphatrane derivatives with good to high isolated yields for the corresponding fluoroazaphosphatranes (70–92%). The scope of the reaction was widened to fluoroazaphosphatranes bearing various substituents and X‐ray molecular structures of two of them are reported. The stability of fluoroazaphosphatranes toward nucleophilic solvents like water has been investigated. As they revealed much more robust cations than their chloroazaphosphatrane parents, their chloride salts were tested as organocatalysts for the formation of cyclic carbonates from epoxides and CO2. Fluoroazaphosphatranes proved to be both efficient and stable catalytic systems for CO2 conversion with catalytic activities similar to those of azaphosphatranes, and no decomposition of the cation was observed at the end of reaction. [ABSTRACT FROM AUTHOR]

Cryptophane cages can adopt either an anti or syn configuration that present different recognition properties. While the synthesis of anti-cryptophanes is well reported, the synthesis of syn-cryptophanes remains a challenge. Herein, we demonstrate that the use of HFIP as a co-solvent during the second ring closure reaction significantly affects the regioselectivity, providing easier access to the syn-cryptophane stereomers. [ABSTRACT FROM AUTHOR]

Azaphosphatranes were found to act as efficient organocatalysts in the presence of water for the cyanation of differently substituted imines. A relatively safer source of cyanide, trimethylsilyl cyanide (TMSCN), was used, and excellent yields could be obtained with only 0.05 mol % of catalyst. The influence of acidity of azaphosphatranes on catalytic activity as well as the role of azaphosphatranes in the mechanism of the reaction were also investigated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The synthesis of a hemicryptophane cage combining a CTV unit with a C3 symmetrical moiety bearing three urea functions is reported. This host was found to bind anions with higher binding constants than other previously reported hemicryptophanes. Due to its heteroditopic character this cage proved to be an efficient ion‐pair receptor. The best cooperativity effect was observed for the tetramethylammonium bromide (TMABr) salt, which was confirmed and rationalized by DFT calculations. A tris‐urea unit was combined with CTV moiety, leading to a heteroditopic hemicryptophane capable of binding ion pairs efficiently and selectively. [ABSTRACT FROM AUTHOR]

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. 31P NMR spectroscopy and mass spectrometry experiments evidenced that no interaction between the Lewis acidic and basic partners occurred when the superbase was capped by a cycloveratrylene (CTV) unit, thus creating a true FLP active system. [ABSTRACT FROM AUTHOR]

Proazaphosphatranes, also known as Verkade's superbases, have been investigated as ligands for gold(I). If the coordination to the gold center by the phosphorus atom suggests phosphine-like behavior, gold(I)-containing Verkade's superbase complexes could also be prepared from the weak conjugate acid azaphosphatrane by the formation of the corresponding silver complex and subsequent transmetalation to gold, similarly to the synthetic route used for complexes bearing N-heterocyclic carbene ligands (NHCs). A competitive transmetalation experiment highlighted the higher lability of Verkade's superbases compared with NHCs. Furthermore, combined theoretical and experimental studies showed that they display strong s-donor ability, better than phosphines and similar to NHCs. Thus, some specific properties of both NHCs and phosphines are combined in Verkade's superbases, thereby providing a new approach to tuning the ligand properties of gold(I) complexes. [ABSTRACT FROM AUTHOR]

Four new enantiopure hemicryptophanes were synthesized and their absolute configuration was determined from experimental and calculated ECD spectra. Complexation properties of these receptors were studied toward six carbohydrate stereoisomers derived from glucose, galactose and mannose. All the receptors showed a better affinity for α-mannoside with association constants up to 2.5 × 103 M−1. One of the receptor can complex almost exclusively α-mannoside facing to α-galactoside. [ABSTRACT FROM AUTHOR]

Enantiopurehemicryptophanes designed from the cyclotriveratrylene(CTV) unit display remarkable properties in selective host–guestrecognition or as supramolecular catalysts. The unprecedented controlof the helical chirality of the CTV unit by remote stereogenic centersof a tren moiety is reported, providing an original access to thishighly promising class of host molecules. Although the chiral centersand the CTV unit are separated by more than 10 Å, one singlediastereomer is formed; the nature of the diastereoselective processis discussed and the procedure is exemplified using different enantiopuretren derivatives. This work also highlights the influence of the chiralityof the CTV unit on the whole cage structure. [ABSTRACT FROM AUTHOR]

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. The use of an encaged superbase as organocatalyst is unprecedented and highlights how the confinement may impact the stereoselectivity. [ABSTRACT FROM AUTHOR]

A novel N-substituted azaphosphatrane molecular precursor bearing an alkyne tether was synthesized using a multi-step strategy and covalently immobilized onto SBA-15 type silica through triazole linkages by means of the well-known click chemistry. The resulting hybrid material, [7]@SBA-15, was characterized well by methods appropriate to molecular species (e.g. solid state 13C, 31P and 29Si NMR, infrared spectroscopy and elemental analysis) as well as techniques more commonly associated with the characterization of mesoporous solids (nitrogen sorption isotherms, powder X-ray diffraction, TGA analysis). The catalytic activity of [7]@SBA-15 was then evaluated in the coupling of CO2 with two epoxides (styrene oxide and epichlorohydrin) and compared to its monotriazole modified AZAP molecular analog, 8. This work represents the first example of silica modified N-substituted azaphosphatrane for the production of cyclic carbonates. [ABSTRACT FROM AUTHOR]

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 CO 2 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. [ABSTRACT FROM AUTHOR]

Abstract: Various N-substituted azaphosphatranes have been prepared and successfully applied to the synthesis of styrene carbonates from CO2 and epoxides. Enhancement of the catalytic properties of the azaphosphatrane was achieved upon pre-organization of the active site through hydrogen-bonding. [Copyright &y& Elsevier]

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 [ABSTRACT FROM AUTHOR]

ABSTRACT Enantiopure hemicryptophanes efficiently discriminate chiral ammonium neurotransmitters. The ephedrine and norephedrine molecules associate with hemicryptophane hosts to form 1:1 and 1:2 host-guest complexes. Binding constants are determined by fitting the 1H (NMR) titration curves to give β1 and β2 values, which are used to characterize the diastereomeric and enantiomeric discriminating potentials of the hosts. Chirality 25:47-479, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACT The hemicryptophane racemate (±)- M-1 P-1 was optically resolved by semipreparative HPLC on Chiralpak IC column. The absolute configuration of each isolated enantiomer was established from the analysis of their electronic circular dichroism spectra. Enantiodifferentiation of the chiral cationic cage (±)- M-1 P-1 was evidenced in solution using Δ-TRISPHAT as chiral solvating agent, and the diastereomeric associations were observed in 1H and 31P NMR spectra. Chirality 24:1077-1081, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The design of molecular cages with low symmetry could allow for more specific tuning of their properties and better mimic the unsymmetrical and complex environment of protein pockets. However, the added value of lowering symmetry of molecular receptors has been rarely demonstrated. Herein, C 3 - and C 1 -symmetrical cages, presenting the same recognition sites, have been synthesized and investigated as hosts for carbohydrate recognition. Structurally related derivatives of glucose, galactose and mannose were found to have greater affinity to the receptor with the lowest symmetry than to their C 3 -symmetrical analogue. According to the host cavity modelling, the C 1 symmetry receptor exhibits a wider opening than its C 3 -symmetrical counterpart, providing easier access and thus promoting guest proximity to binding sites. Moreover, our results show the high stereo- and substrate selectivity of the C 1 symmetry cage with respect to its C 3 counterpart in the recognition of sugars., (© 2022 Wiley-VCH GmbH.)

The globular and monocationic guest molecule trimethyl-azaphosphatrane (AZAP, a protonated Verkade superbase) was shown to form a host:guest 1 : 1 complex with the cucurbit[10]uril (CB[10]) macrocycle in water. Molecular dynamics calculations showed that CB[10] adopts an 8-shape with AZAP occupying the majority of the internal space, CB[10] contracting around AZAP and leaving a significant part of the cavity unoccupied. This residual space was used to co-include planar and monocationic co-guest (CG) molecules, affording heteroternary CB[10]⋅AZAP⋅CG complexes potentially opening new perspectives in supramolecular chemistry., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

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. Verkade, the first synthesis of fluoroazaphosphatranes was only described in 2018 by Stephan et al. Currently, no common and versatile procedure exists to access fluoroazaphosphatranes platform with different structural characteristics. In this report, a new and simple synthesis of this class of compounds was developed based on the nucleophilic attack of the fluoride anion on chloroazaphosphatrane derivatives with good to high isolated yields for the corresponding fluoroazaphosphatranes (70-92%). The scope of the reaction was widened to fluoroazaphosphatranes bearing various substituents and X-ray molecular structures of two of them are reported. The stability of fluoroazaphosphatranes toward nucleophilic solvents like water has been investigated. As they revealed much more robust cations than their chloroazaphosphatrane parents, their chloride salts were tested as organocatalysts for the formation of cyclic carbonates from epoxides and CO 2 . Fluoroazaphosphatranes proved to be both efficient and stable catalytic systems for CO 2 conversion with catalytic activities similar to those of azaphosphatranes, and no decomposition of the cation was observed at the end of reaction., (© 2022 Wiley-VCH GmbH.)

Two new hemicryptophanes combining a cyclotriveratrylene unit with either an aminotrisamide or a tris(2-aminoethyl)amine (tren) moiety have been synthesized. Although a conventional synthesis approach was used, the molecular cages obtained are devoid of the expected C 3 symmetry. NMR analyses and X-ray crystal structure determination showed that these hemicryptophanes exhibited C 1 symmetry due to the unusual arrangement of the substituents of the cyclotriveratrylene unit. This unprecedented arrangement is related to a change in the regioselectivity of the Friedel-Crafts reactions that led to the CTV cap. This constitutes an original approach to access enantiopure chiral molecular cages with low symmetry.

Chloroazaphosphatranes, the corresponding halogenophosphonium cations of the Verkade superbases, were evaluated as a new motif for halogen bonding (XB). Their modulable synthesis allowed for synthetizing chloroazaphosphatranes with various substituents on the nitrogen atoms. The binding constants determined from NMR titration experiments for Cl - , Br - , I - , AcO - , and CN - anions are comparable to those obtained with conventional iodine-based monodentate XB receptors. Remarkably, the protonated azaphosphatrane counterparts display no affinity for anions under the same conditions. The strength of the XB interaction is, to some extent, related to the basicity of the corresponding Verkade superbase. The halogen bonding abilities of this new class of halogen donor motif were also revealed by the Δδ( 31 P) NMR shift observed in CD 2 Cl 2 solution in the presence of triethylphosphine oxide (TEPO). Thus, chloroazaphosphatranes constitute a new class of halogen bond donors, expanding the repertory of XB motifs mainly based on C Ar -I bonds.

A highly selective recognition of fluoride was achieved through the design of a small hemicryptophane cage ( 3 ) presenting a southern tris-urea hosting moiety. The resulting host-guest complex has been characterized by electrospray ionization-high-resolution mass spectrometry, 1 H and 19 F NMR, and X-ray diffraction techniques. In particular, X-ray diffraction analysis of [ 3 ·F - ] reveals that the encapsulation of one fluoride, within 3 , occurs through NH···F - H-bonding with the six NH residues of the tris-urea ligand. An association constant of 1200 M -1 was extracted from 1 H NMR titration experiments, indicating that efficient fluoride binding also occurs in solution. Finally, in sharp contrast with previously reported urea-based hemicryptophane hosts, the small preorganized cavity found in 3 allows for an exclusive selectivity for fluoride over other competing halides.

We report on the synthesis of C 3 -symmetric enantiopure cage molecules 1 , 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 1 are used. Furthermore, protonation/deprotonation induces a reversible modification of the conformation of 1 , which switches from an imploded to an inflated form, leading to ejection and reuptake of the guest initially encaged inside the cavity.

The synthesis of a hemicryptophane cage combining a CTV unit with a C 3 symmetrical moiety bearing three urea functions is reported. This host was found to bind anions with higher binding constants than other previously reported hemicryptophanes. Due to its heteroditopic character this cage proved to be an efficient ion-pair receptor. The best cooperativity effect was observed for the tetramethylammonium bromide (TMABr) salt, which was confirmed and rationalized by DFT calculations., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Enantiopure hemicryptophanes efficiently discriminate chiral ammonium neurotransmitters. The ephedrine and norephedrine molecules associate with hemicryptophane hosts to form 1:1 and 1:2 host-guest complexes. Binding constants are determined by fitting the ¹H nuclear magnetic resonance (NMR) titration curves to give β₁ and β₂ values, which are used to characterize the diastereomeric and enantiomeric discriminating potentials of the hosts., (Copyright © 2013 Wiley Periodicals, Inc.)

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. The size, shape, and functionalities of the molecular cavity were also easily modified., (© 2011 American Chemical Society)