Differential Adsorption of l- and d-Lysine on Achiral MFI Zeolites as Determined by Synchrotron X-Ray Powder Diffraction and Thermogravimetric Analysis

Reported here is the first crystallographic observation of stereospecific bindings of l - and d -lysine (Lys) in achiral MFI zeolites. The MFI structure offers inherent geometric and internal confinement effects for the enantiomeric difference in l - and d -Lys adsorption. Notable differences have been observed by circular dichroism (CD) spectroscopy and thermogravimetric analysis (TGA). Distinct l - and d -Lys adsorption behaviours on the H-ZSM-5 framework have been revealed by the Rietveld refinement of high-resolution synchrotron X-ray powder diffraction (SXRD) data and the density-functional theory (DFT) calculations. Despite demonstrating the approach for l - and d -Lys over MFI zeolites at an atomistic resolution, the differential adsorption study sheds light on the rational engineering of molecular interaction(s) with achiral microporous materials for chiral separation purposes.     

Trihydroborates and Dihydroboranes Bearing a Pentacoordinated Phosphorus Atom: Double Ring Expansion To Balance the Coordination States

The first trihydroborate bearing a pentacoordinated phosphorus atom was synthesized as a new P−B bonded compound. Hydride abstraction of the trihydroborate gave an intermediary dihydroborane, which showed hydroboration reactivity and was trapped with pyridine whilst maintaining the P−B bond. The dihydroborane underwent a rearrangement, which involved a double ring expansion to compensate for the unbalanced coordination states of the phosphorus and boron atoms, to give a new fused bicyclic phosphine-boronate.     

Synthesis,Structure, and Reactivity of 5-(Aryl)dibenzothiophenium Triflates

A synthetic protocol for the preparation of 5-(aryl)dibenzothiophenium salts starting from inexpensive dibenzothiophene S-oxide and simple arenes is reported. The scope of the method regarding the nature of the arene is evaluated, intermediates along the reaction sequence have been trapped, and side-reactions identified. In addition, the X-ray structures of a complete set of these salts are reported and their reactivities studied. Specifically, chemoselective Suzuki coupling is observed at the dibenzothiophenium in the presence of iodides.     

Modular Synthesis of Nona-Decasaccharide Motif from Psidium guajava Polysaccharides: Orthogonal One-Pot Glycosylation Strategy

The synthesis of long, branched, and complex carbohydrate sequences remains a challenging task in chemical synthesis. Reported here is an efficient and modular one-pot synthesis of a nona-decasaccharide and shorter sequences from Psidium guajava polysaccharides, which have the potent α-glucosidase inhibitory activity. The synthetic strategy features: 1) several one-pot glycosylation reactions on the basis of N-phenyltrifluoroacetimidate (PTFAI) and Yu glycosylation to streamline the chemical synthesis of oligosaccharides, 2) the successful and efficient assembly sequences (first O3′, second O5′, final O2′) toward the challenging 2,3,5-branched Araf motif, 3) the stereoselective 1,2-cis-glucosylation by reagent control, and 4) the convergent [6+6+7] one-pot coupling reaction for the final assembly of the target nona-decasaccharide. This orthogonal one-pot glycosylation strategy can streamline the chemical synthesis of long, branched, and complicated carbohydrate chains.     

Synthesis of Long Oxahelicenes by Polycyclization in a Flow Reactor

A series of oxahelicenes composed of ortho/meta-annulated benzene/pyridine and 2H-pyran rings were synthesized on the basis of the cobalt(I)-mediated (or rhodium(I)- or nickel(0)-mediated) double, triple, or quadruple [2+2+2] cycloisomerization of branched aromatic hexa-, nona-, or dodecaynes, thus allowing the construction of 6, 9, or 12 rings in a single operation. The use of a flow reactor was found to be beneficial for the multicyclization reactions. The stereogenic centers present in some of the oligoynes steered the helical folding in such a way that the final oxa[9]-, [13]-, [17]- and [19]helicenes were obtained in both enantiomerically and diastereomerically pure form. Specifically, the oxa[19]helicenes beat the current record in the length of a helicene backbone. Single-molecule conductivity was studied by the mechanically controllable break-junction method with a pyridooxa[9]helicene.     

Biopolymer Skeleton Produced by Rhizobium radiobacter: Stoichiometric Alternation of Glycosidic and Amidic Bonds in the Lipopolysaccharide O-Antigen

The lipopolysaccharide (LPS) O-antigen structure of the plant pathogen Rhizobium radiobacter strain TT9 and its possible role in a plant-microbe interaction was investigated. The analyses disclosed the presence of two O-antigens, named Poly1 and Poly2. The repetitive unit of Poly2 constitutes a 4-α-l -rhamnose linked to a 3-α-d -fucose residue. Surprisingly, Poly1 turned out to be a novel type of biopolymer in which the repeating unit is formed by a monosaccharide and an amino-acid derivative, so that the polymer has alternating glycosidic and amidic bonds joining the two units: 4-amino-4-deoxy-3-O-methyl-d -fucose and (2′R,3′R,4′S)-N-methyl-3′,4′-dihydroxy-3′-methyl-5′-oxoproline). Differently from the O-antigens of LPSs from other pathogenic Gram-negative bacteria, these two O-antigens do not activate the oxidative burst, an early innate immune response in the model plant Arabidopsis thaliana, explaining at least in part the ability of this R. radiobacter strain to avoid host defenses during a plant infection process.     

Strategy for the Construction of Diverse Poly-NHC-Derived Assemblies and Their Photoinduced Transformations

A series of supramolecular assemblies of types [Ag₈( L )₄](PF₆)₈ and [Ag₄( L )₂](PF₆)₄, obtained from the tetraphenylethylene (TPE) bridged tetrakis(1,2,4-triazolium) salts H₄-L(PF₆)₄ and Ag^I ions, is described. The assembly type obtained dependends on the N-wingtip substituents of H₄-L(PF₆)₄. Changes in the lengths of the N4-wingtip substituents enables controlled formation of assemblies with either [Ag₄( L )₂](PF₆)₄ or [Ag₈( L )₄](PF₆)₈ stoichiometry. The molecular structures of selected [Ag₈( L )₄](PF₆)₈ and [Ag₄( L )₂](PF₆)₄ assemblies were determined by X-ray diffraction analyses. While H₄- L (PF₆)₄ does not exhibit fluorescence in solution, their tetra-NHC (NHC=N-heterocyclic carbene) assemblies do upon NHC–metal coordination. Upon irradiation, all assemblies undergo a light-induced, supramolecule-to-supramolecule structural transformation by an oxidative photocyclization involving phenyl groups of the TPE core, resulting in a significant change of the luminescence properties.     

Synthesis and Characterization of Fluorodinitroamine,FN(NO2)2

NF₃ and N(NO₂)₃ are known compounds, whereas the mixed fluoronitroamines, FN(NO₂)₂ and F₂NNO₂, have been unknown thus far. One of these, FN(NO₂)₂, has now been prepared and characterized by multinuclear NMR and Raman spectroscopy. FN(NO₂)₂ is the first known example of an inorganic fluoronitroamine. It is a thermally unstable, highly energetic material formed by the fluorination of the dinitramide anion using NF₄⁺ salts as the preferred fluorinating agent.     

Synthesis of Substituted 1,2,4-Triazoles and 1,3,4-Thiadiazoles

The cyclization of 4-substituted 1-arylacetyl- and 1-aryloxyacetylthiosemicarbazides and also the potassium salt of (4-bromophenoxy)acetodithiocarbazinic acid in the presence of base gives the novel 3-arylmethyl- and 3-aryloxymethyl-5-mercapto-1,2,4-triazoles and, in the presence of concentrated H₂SO₄, the novel 5-substituted 2-arylmethyl- and 2-aryloxymethyl-1,3,4-thiadiazoles.     

Facile Synthesis of Hierarchical Nanosized Single-Crystal Aluminophosphate Molecular Sieves from Highly Homogeneous and Concentrated Precursors

The synthesis of hierarchical nanosized zeolite materials without growth modifiers and mesoporogens remains a substantial challenge. Herein, we report a general synthetic approach to produce hierarchical nanosized single-crystal aluminophosphate molecular sieves by preparing highly homogeneous and concentrated precursors and heating at elevated temperatures. Accordingly, aluminophosphate zeotypes of LTA (8-rings), AEL (10-rings), AFI (12-rings), and -CLO (20-rings) topologies, ranging from small to extra-large pores, were synthesized. These materials show exceptional properties, including small crystallites (30–150 nm), good monodispersity, abundant mesopores, and excellent thermal stability. A time-dependent study revealed a non-classical crystallization pathway by particle attachment. This work opens a new avenue for the development of hierarchical nanosized zeolite materials and understanding their crystallization mechanism.     

A Symmetric Co(N5)2(H2O)4⋅4 H2O High‐Nitrogen Compound Formed by Cobalt(II) Cation Trapping of a Cyclo‐N5− Anion

The reactions of (N₅)₆(H₃O)₃(NH₄)₄Cl with Co(NO₃)₂⋅6 H₂O at room temperature yielded Co(N₅)₂(H₂O)₄⋅4 H₂O as an air‐stable orange metal complex. The structure, as determined by single‐crystal X‐ray diffraction, has two planar cyclo‐N₅⁻ rings and four bound water molecules symmetrically positioned around the central metal ion. Thermal analysis demonstrated the explosive properties of the material.     

Facile Synthesis of Dihydro-1,2,4-benzotriazepin-5-ones

Summary. Direct interaction between model anilines and an 1,3-dipolar nitrile imine, derived from 2-[N′-(1-chloro-2-oxopropylidine)hydrazine]benzoic acid, yielded the respective acyclic amidrazones. The latter adducts underwent CDI-induced cyclocondensation involving the hydrazone–NH terminus and the activated carboxy group to produce the corresponding dihydro-1,2,4-benzotriazepin-5-ones.     

酰胺基硫脲和1,2,4-三唑的合成和生物活性

设计并合成了１６个酰胺基硫脲类化合物的１４个１、２、４－三唑－５－硫醇类化合物。生物活性初筛试验表明,两类化合物对水稻和黄瓜幼苗有一定的生长调节活性。     

Dinitramidoborates: A Fascinating Case of Competing Oxygen and Nitrogen Donors and Tautomerism

Reactions of the BH₄⁻ anion with equimolar amounts of HN(NO₂)₂ or of BH₃⋅THF with K[N(NO₂)₂]⁻ produced a mono‐substituted [BH₃N(NO₂)₂]⁻ anion, which contains a B−N connected dinitramido ligand. The reaction of BH₄⁻ with two equivalents of HN(NO₂)₂ afforded the di‐substituted borate anion consisting of two isomers, one with both nitramido ligands attached to B through N and the other one with one ligand attached through N and the other one through O. The disubstituted dinitramidoborates are marginally stable under ambient conditions, and the isomer with two N‐connected ligands was characterized by its crystal structure. A tri‐substituted borate was tentatively identified by NMR in the reaction of BH₄⁻ with a large excess of HN(NO₂)₂. All of the anions are highly energetic. Theoretical calculations show that the energy differences between the B−N and B−O tautomers are small, explaining the formation of both.     

Metal-Free Synthesis of Functional 1-Substituted-1,2,3-Triazoles from Ethenesulfonyl Fluoride and Organic Azides

The boom in growth of 1,4-disubstituted triazole products, in particular, since the early 2000’s, can be largely attributed to the birth of click chemistry and the discovery of the Cu^I-catalyzed azide–alkyne cycloaddition (CuAAC). Yet the synthesis of relatively simple, albeit important, 1-substituted-1,2,3-triazoles has been surprisingly more challenging. Reported here is a straightforward and scalable click-inspired protocol for the synthesis of 1-substituted-1,2,3-triazoles from organic azides and the bench stable acetylene surrogate ethenesulfonyl fluoride (ESF). The new transformation tolerates a wide selection of substrates and proceeds smoothly under metal-free conditions to give the products in excellent yield. Under controlled acidic conditions, the 1-substituted-1,2,3-triazole products undergo a Michael addition reaction with a second equivalent of ESF to give the unprecedented 1-substituted triazolium sulfonyl fluoride salts.