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A highly efficient method to oxidize methylarenes to their corresponding acids with a reusable Cr catalyst was developed. The reaction can be carried out in water with 1 atm oxygen and K2S2O8 as cooxidants, proceeds under green and mild conditions, and is suitable for the oxidation of both electron-deficient and electron-rich methylarenes, including heteroaryl methylarenes, even at the gram level. The excellent result, together with its simplicity of operation and the ability to continuously reuse the catalyst, makes this new methodology environmentally benign and cost-effective. The generality of this methodology gives it the potential for use on an industrial scale. Differing from the accepted oxidation mechanism of toluene, GC-MS studies and DFT calculations have revealed that the key benzyl alcohol intermediate is formed under the synergetic effect of the chromium and molybdenum in the Cr catalyst, which can be further oxidized to afford benzaldehyde and finally benzoic acid. [ABSTRACT FROM AUTHOR]

A simple and efficient protocol for the formylation of amines with formic acid, catalyzed by a polyoxometalate-based chromium catalyst, is described. Notably, this method shows excellent activity and chemoselectivity for the formylation of primary amines; diamines have also been successfully employed. Importantly, the chromium catalyst is potentially non-toxic, environmentally benign and safer than the widely used high valence chromium catalysts such as CrO3 and K2Cr2O7. The catalyst can be recycled several times with a negligible impact on activity. Finally, a plausible mechanism is provided based on the observation of intermediate and control experiments. [ABSTRACT FROM AUTHOR]

Over the past two decades, there have been major developments in the transition iron-catalyzed selective oxidation of alkenes to epoxides; a common structure found in drug, isolated natural products, and fine chemicals. Many of these approaches have enabled highly efficient and selective epoxidation of alkenes via the design of specialized ligands, which facilitates to control the activity and selectivity of the reactions catalyzed by iron atom. Herein, we report the development of the olefin epoxidation with inorganic-ligand supported iron-catalysts using 30% H2O2 as an oxidant, and the mechanism is similar to iron-porphyrin type. With the catalyst 1, (NH4)3[FeMo6O18(OH)6], various aromatic and aliphatic alkenes were successfully transformed into the corresponding epoxides with excellent yields as well as chemo- and stereo-selectivity. This catalytic system possesses the advantages of being able to avoid the use of expensive, toxic, air/moisture sensitive and commercially unavailable organic ligands. The generality of this methodology is simple to operate and exhibits high catalytic activity as well as excellent stability, which gives it the potential to be used on an industrial scale, and maybe opens a way for the catalytic oxidation reaction via inorganic-ligand coordinated iron catalysis. [ABSTRACT FROM AUTHOR]

In this work, we confirmed that the copper-catalysed azide–alkyne cycloaddition (CuAAC) reaction is an effective method for the organic-functionalization of polyoxometalates (POMs). Herein, for the first time, four novel 1,2,3-triazole functionalized polyoxovanadate (POV) organic–inorganic hybrids, (Bu4N)2[V6O13{(OCH2)3C5H6N3O}2]·1.5CH3CN 2, (Bu4N)2[V6O13{(OCH2)3C7H8N3O2}2]·2CH3CN 3, (Bu4N)2[V6O13{(OCH2)3C11H10N3}2] 4 and (Bu4N)2[V6O13{(OCH2)3C10H7N3Cl}2] 5 were prepared through the CuAAC reaction using the azide functionalized hexavanadate, (Bu4N)2[V6O13{(OCH2)3CCH2N3}2]·2.5CH3CN 1, as the precursor, where CuI was used as the catalyst and N,N-diisopropylethylamine (DIPEA) as a stabilizer for CuI. All the four compounds were structurally and compositionally characterized by single-crystal X-ray diffraction, elemental analyses, powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), 1H NMR, ESI-MS, UV-Vis and thermogravimetric analysis (TGA). [ABSTRACT FROM AUTHOR]

A new synthetic approach to tri-substituted trisalkoxy-hexavanadate clusters containing different organic groups was developed in this work. Four mixed-valence or fully reduced POV hybrids were synthesized and structurally characterized, including an amino-containing derivative of hexavanadate, Na2[VIV3VV3O10{NH2C(CH2O)3}3] (1). Furthermore, a novel mixed-valence POV hybrid was prepared via the amidation of 1, indicating that 1 can be used as an excellent building block for the design and synthesis of mixed-valence POV functional materials. [ABSTRACT FROM AUTHOR]

A reaction strategy for the post-functionalization of hexavanadate derivatives is presented herein. In this study, five polyoxovanadate-based organic–inorganic hybrids TBA2[V6O13{(OCH2)3CCOO(CH2)15CH3}2] (2), TBA2[V6O13{(OCH2)3CCOO(CH2)8CH=CH2}2] (3), TBA2[V6O13{(OCH2)3CCOOCH2CF3}2] (4), TBA2[V6O13{(OCH2)3CCOO(CH2CH2O)3CH3}2] (5), and TBA2[V6O13{(OCH2)3CCOO(CH2)12OH}2]·2CH3CH2OH (6) were successfully synthesized via esterification of carboxylic acid groups-containing TBA2[V6O13{(OCH2)3CCOOH}2] (1) with five alcohols possessing different functional groups. These hybrids were characterized by single crystal X-ray diffraction, IR, ESI-MS, 1H and 13C-NMR spectroscopies, and elemental analysis. Moreover, the formation of large vesicles was observed in a mixed solution of compound 2 due to its surfactant-like structure. [ABSTRACT FROM AUTHOR]

A class of monoorganoimido-substituted hexamolybdates containing a pyridine group have been firstly synthesized. Furthermore, a reaction protocol of alkylation based on the resulting pyridine-functionalized hexamolybdates has been developed, with which a type of zwitterionic clusters has been successfully obtained. [ABSTRACT FROM AUTHOR]

Monofunctionalized alkylimido derivatives of hexamolybdate, (Bu4N)2[Mo6O18(≡N–R)] (R = methyl, Me; ethyl, Et; n-propyl, n-Pr; i-propyl, i-Pr; n-butyl, n-Bu; t-butyl, t-Bu; cyclohexyl, Cy; n-hexyl, Hex; and n-octadecyl, Ode), have been prepared in high purity and good yield by the reaction of [Bu4N]4[α-Mo8O26] with appropriate aliphatic amine hydrochlorides in anhydrous acetonitrile, using N,N′-dicyclohexylcarbodiimide (DCC) as the dehydrating agent. Eight compounds have been determined by single crystal X-ray diffraction analysis and all compounds have been studied with 1H-NMR, IR, UV-vis, ESI mass spectrometry and cyclic voltammetry. A structural and 1H-NMR study show β hydrogen atoms of those alkylimido derivatives of hexamolybdate have strong Brønsted acidity compared to the hydrogen atoms in other positions. [ABSTRACT FROM AUTHOR]

Correction for ‘Diversified polyoxovanadate derivatives obtained by copper(i)-catalysed azide–alkyne cycloaddition reaction: their synthesis and structural characterization’ by Hongli Jia et al., Dalton Trans., 2018, 47, 577–584. [ABSTRACT FROM AUTHOR]