The combination of racemic praziquantel, (RS)-PZQ, with aliphatic dicarboxylic acids of the homologous series HOOC−(CH 2 ) n −COOH (with n = 0−8) and the unsaturated analogues of succinic acid as cocrystal formers via liquid-assisted grinding provided a total of nine 1:1 and 2:1 cocrystals with oxalic acid, malonic acid, succinic acid (two polymorphic phases), maleic acid, fumaric acid, glutaric acid, adipic acid, and pimelic acid. The cocrystalline phases were identified first by XRPD analysis and then structurally characterized by IR spectroscopy and, as far as possible, by single-crystal X-ray diffraction analysis. Crystals suitable for XRD analysis were obtained for seven cocrystals and, additionally, for (RS)-PZQ. The analysis of the supramolecular interactions in the crystal structures has shown that the dominant hydrogen bonding patterns within the cocrystals are heterodimeric motifs formed through O−H•••O hydrogen bonds between PZQ and the dicarboxylic acids, which mostly contain additionally at least one secondary C−H•••O contact. In all crystal structures, the PZQ molecules are connected with each other through cyclic homodimeric hydrogen bonding interactions formed mainly through C−H•••O, but also through C−H•••π contacts, giving overall 1D, 2D or 3D hydrogen bonded networks. The crystallographic study also allowed us to establish that there are two main rotational conformers for PZQ, which differ in the configuration of the CO groups in the piperazinone−cyclohexylcarbonyl segment. In the crystal structure of (RS)-PZQ, all four independent molecules in the asymmetric unit have the syn-conformation, which in the hemihydrates, viz. (R)-PZQ•0.5H 2 O and (S)-PZQ•0.5H 2 O, and all cocrystals except for one are switched to the anti-antagonist.

The combination of one dipyridyl linker [1,2-di(4-pyridyl)ethylene (DPE), 1,2-di(4-pyridyl)ethane (DPEt), or 4,4′-azopyridine (DPA)] with two molecules of arylboronate ester 1 produced dinuclear Lewis-type N→B adducts that can act as acyclic host for polycyclic aromatic hydrocarbons (PAHs) in the solid state. Nine crystalline solids of composition PAH@adduct (i.e., one PAH per adduct) were obtained from solutions containing a single PAH. On the basis of the single-crystal X-ray diffraction analysis of the compound ANT@A1 (ANT = anthracene; A1 = adduct being composed of DPE and two boronate esters 1), the PAH inclusion selectivity is related to a size-fitting adaptation to an octaedral-shaped pocket assembled by CH-π interactions between fragments of the diamine and the arylboronate ester 1. The resulting reversible organic clathrates can perform "catch and release" cycles of PAHs such as pyrene and can sequester selectively PAHs from mixtures in solution.T he molecular recognition of polycyclic aromatic hydrocarbons (PAHs) is a challenging issue given the variety of sizes, shapes, and properties of these widespread materials. 1 PAHs are among the most intensively studied pollutants in the environmental analysis of air, water, food, and solid-waste samples. Methods for quantitative separation and detection of PAHs often rely on traditional chromatographic and solventextraction protocols. 2 A well-established supramolecular approach to bind PAHs in solution consists of the use of polycationic macrocycles and cages derived from extended viologens, which are assembled covalently 3 or through metal coordination. 4 The association constants of these host−guest complexes in water and polar solvents range between 10 1 and 10 6 M −1 , and a significant number of X-ray crystal structures of such complexes has been reported. Yet these elegant supramolecular receptors were made in multistep synthetic procedures 3 or involved costly transition metals. 4 Thus, it is still a demanding task to develop simple methods to selectively detect PAHs, and also to be able to recover them quantitatively as a single (or multiple) PAH from mixtures in solution. 1,2 In the past decade, various research groups have comprehensively explored the interaction of aromatic amines with boronate esters and boroxines to provide a broad variety of discrete and polymeric materials, such as macrocycles, 5 nanostructures, 6 coordination polymers, 7 and gels. 8 Hence, supramolecular assembly based on dative N→B interactions is recognized as a useful strategy for the generation of complex systems, and given its thermodynamic stability (−11 to −38 kJmol −1 ) 6,7 and kinetic lability in polar coordinating solvents, the central N→B binding motif can be compared to a typical noncovalent interaction. The potential of this approach is well exemplified by the prismatic organic cages assembled via N→B bonds that were able to encapsulate triphenylene or coronene in the solid state. 6c These previous reports have also evidenced that simple arylmonoboronate esters ...

This contribution describes metal-organic frameworks based on cadmium-clusters that are capable of generating doublepillared architectures. A brief overview of the literature concerning such systems is presented together with the description of three new coordination polymers, [{[Cd 2 (trans-1,2-a,achdc)(trans-1,2-e,e-chdcH) 2 (4,4Ј-bpy) 2 ]·8H 2 O} n ] (1), [{Cd 2 -(trans-1,4-e,e-chdc)(trans-1,4-a,a-chdc)(4,4Ј-bpe) 2 } n ] (2)

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Abstract:An efficient synthesis of enantiomerically-pure β-aryl-γ-lactams is described. The principal feature of this synthesis is the practical resolution of β-aryl-γ-lactams with (S)-Naproxen. The procedure is based on the Michael addition of nitromethane to benzylidenemalonates, which was easily obtained, followed by the reduction of the γ-nitroester in the presence of Raney nickel and the subsequent saponification/decarboxylation reaction. The utility of this methodology was highlighted by the preparation of enantiomerically-pure (R)-and (S)-Baclofen hydrochloride.