Dioxomolybdenum(VI) and -Tungsten(VI) Amino Bisphenolates as Epoxidation Catalysts

Low-cost metallate salts Na2MO4 center dot 2H(2)O (M = molybdenum, tungsten) react with a tridentate amine bisphenol bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)methylamine (H2ONOtBu) under ambient conditions in acidic methanol solutions. The reactions lead to the formation of isostructural dioxo complexes [MO2(ONOtBu)(MeOH)]center dot MeOH in convenient yields. Spectral data as well as X-ray analyses reveal these complexes to be isostructural. Both compounds were tested as catalysts for epoxidation of olefins using cis-cyclooctene, cyclohexene, norbornene and styrene as substrates and tert-butyl hydroperoxide and hydrogen peroxide as oxidants. The molybdenum complex catalyses selectively the oxidation of cis-cyclooctene and norbornene to corresponding epoxides, whereas oxidation of cyclohexene and styrene lead low yields as the epoxidations were associated with the formation of other oxidation products. Corresponding tungsten complex shows lower activity for epoxidation of norbornene and practically no activity for other olefins. Both complexes can also catalyse the conversion of benzoin to benzil using dimethyl sulphoxide as an oxidant, while the molybdenum complex shows higher activity

Halogen bonds, chalcogen bonds, pnictogen bonds, tetrel bonds and other σ-hole interactions: a snapshot of current progress

We report here on the status of research on halo­gen bonds and other σ-hole inter­actions involving p-block elements in Lewis acidic roles, such as chalcogen bonds, pnictogen bonds and tetrel bonds. A brief overview of the available literature in this area is provided via a survey of the many review articles that address this field. Our focus has been to collect together most review articles published since 2013 to provide an easy entry into the extensive literature in this area. A snapshot of current research in the area is provided by an introduction to the virtual special issue com­piled in this journal, com­prising 11 articles and entitled `Halogen, chalcogen, pnictogen and tetrel bonds: structural chemistry and beyond.

Oxidovanadium(v) complexes with L-proline-based amino acid phenolates

L-proline was used to prepare chiral, tridentate amino acid phenol proligands H2L1-4. These proligands react with vanadium precursors VO(acac)(2,) VOSO4 center dot 5H(2)O and VO(OPr)(3) in methanol to form the corresponding oxidoalkoxidovanadium(v) complexes 1-4. The complexes crystallize from methanol, and are octahedrally co-ordinated with a general formula [VO(L1-4)(OMe)(MeOH)]. In solution, however, they adopt several different conformations or isomeric structures depending on the solvent

Dioxidomolybdenum(VI) and -tungsten(VI) complexes with tetradentate amino bisphenolates as catalysts for epoxidation

Sixteen molybdenum and tungsten complexes with tripodal or linear tetradentate amino bisphenol ligands were studied as catalysts for the epoxidation of cis-cyclooctene, 1-octene, styrene, limonene and alpha-terpineol. These complexes can be divided into different categories upon key features, i.e. central metal (Mo versus W), side-arm donor (O versus N), hybridization of the N-donor (pyridine versus amine), ligand geometry (tripodal versus linear diamine) and sterical hindrance (Me versus tert-Bu substituents in the phenol part). All complexes can catalyse selectively the epoxidation of cis-cyclooctene by tert-butylhydroperoxide whereas the activities and selectivities towards other olefins (1-octene, styrene, limonene and cc-terpineol) show large differences. When H2O2 was used as an oxidant in the epoxidation of cis-cyclooctene, only two of eight Mo complexes and four of eight W complexes showed any activity. This study revealed no clear correlations between the Mo and W catalyst structures and their activities. (c) 2017 Elsevier Ltd. All rights reserved

Dioxidomolybdenum(VI) and -tungsten(VI) complexes with tetradentate amino bisphenolates as catalysts for epoxidation

Sixteen molybdenum and tungsten complexes with tripodal or linear tetradentate amino bisphenol ligands were studied as catalysts for the epoxidation of cis-cyclooctene, 1-octene, styrene, limonene and α-terpineol. These complexes can be divided into different categories upon key features, i.e. central metal (Mo versus W), side-arm donor (O versus N), hybridization of the N-donor (pyridine versus amine), ligand geometry (tripodal versus linear diamine) and sterical hindrance (Me versus tert-Bu substituents in the phenol part). All complexes can catalyse selectively the epoxidation of cis-cyclooctene by tert-butylhydroperoxide whereas the activities and selectivities towards other olefins (1-octene, styrene, limonene and α-terpineol) show large differences. When H2O2 was used as an oxidant in the epoxidation of cis-cyclooctene, only two of eight Mo complexes and four of eight W complexes showed any activity. This study revealed no clear correlations between the Mo and W catalyst structures and their activities.peerReviewe

One‐pot synthesis of [2+2]‐helicate‐like macrocycle and 2+4‐μ4‐oxo tetranuclear open frame complexes : Chiroptical properties and asymmetric oxidative coupling of 2‐naphthols

Synthesis of binuclear Cu(II) terminally closed [2+2]‐ double‐stranded helicate‐like macrocycles 1, 1′,1″, 2, 2′, 2″ and 2+4‐μ4‐oxo tetranuclear open frame complexes 3, 3′, 3″, 4, 4′, 4″ are established. Adapting one‐pot self‐assembly technique from simple three components systems: 1,1′‐binaphthyl‐2,2′‐diamine, 4‐methyl‐2,6‐diformyl phenol and cupric salts, the helicate‐like [2+2]‐ macrocyclic complexes 1–1″, 2–2″ and 2+4‐μ4‐oxo tetranuclear complexes 3–3″, 4–4″ were obtained by appropriately altering the reaction condition such as temperature and subcomponent ratio. Density Functional Theory (DFT) calculations were carried out for understanding the structural geometries, intermediates involved in the diverse formation of [2+2] and 2+4 frameworks. The single crystal X‐ray structures obtained for 1′, 2 and 3 confirms the self‐assembly process in line with DFT. This detailed analysis tempted us to derive a plausible mechanism for this long standing challenge in the synthesis of such macrocycles using 1,1′‐binaphthyl‐2,2′‐diamine (BNDA) and aromatic aldehyde. The chiroptical properties of enantiopure complexes and their catalytic applications in asymmetric oxidative coupling of 2‐naphthol to chiral 1,1’‐Bi‐2‐naphthol (BINOL) achieved in good yield and ee were discussed.peerReviewe

Synthesis of self-assembled mesoporous 3D In2O3 hierarchical micro flowers composed of nanosheets and their electrochemical properties

This report describes the methodology for the fabrication of mesoporous In2O3 microflowers by hydrothermal and calcination procedures in which In(OH)(3)/In2S3 acts as an intermediate. Both In2O3 and its precursor were analyzed with scanning electron microscopy, energy dispersive X-ray spectrophotometry, transmission electron microscopy and powder X-ray diffraction. BET surface area, pore size and pore volume analyses were also carried out. Electron microscopy images clearly evidence the self-assembly of 2D nanosheets into the micro flower structure. The mechanism of self-assembly and calcination is reported. Electrochemical properties of the synthesized In2O3 micro flowers were studied

Synthesis, characterization, crystal structures and biological screening of 4-amino quinazoline sulfonamide derivatives

Three quinazolin-4-ylamino derivatives containing phenylbenzenesulfonamides (7a-7c) were synthesized by reacting (E)-N'-(2-cyanophenyl)-N,N-dimethyl formamidine (6) with different 4- amino-N-(phenyl)benzenesulfonamides (4a-4c) and characterized by different techniques such as HRMS, IR, 1H NMR and 13C NMR spectroscopy. The structural properties were further examined by single crystal X-ray diffraction method. The X-ray data shows that compounds 7a and 7c contain two molecules and 7b contains one molecule in the asymmetric unit. Comparison of conformation of two distinct molecules, “A” and “B”, in the asymmetric unit of 7a and 7c were studied with the aid of reported literature. The in vitro antiproliferative activity of the compounds was tested against two breast cancer cell lines (MDA-MB-231 and MCF7). Compound 7b observed as a highest potent candidate against MDA-MB-231with IC50 of 5.44 µg/mL. Antimicrobial activity was also screened against bacterial and fungal strains. Compound 7a with chloro substitution was observed as the most potent candidate against the Gram-negative bacterial strains, whereas the compounds showed no significant activity against the fungal strain.peerReviewe