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The tert‐butyl group is a common aliphatic motif extensively employed to implement steric congestion and conformational rigidity in organic and organometallic molecules. Because of the combination of a high bond dissociation energy (~100 kcal mol−1) and limited accessibility, in the absence of directing groups, neither radical nor organometallic approaches are effective for the chemical modification of tert‐butyl C−H bonds. Herein we overcome these limits by employing a highly electrophilic manganese catalyst, [Mn(CF3bpeb)(OTf)2], that operates in the strong hydrogen bond donor solvent nonafluoro‐tert‐butyl alcohol (NFTBA) and catalytically activates hydrogen peroxide to generate a powerful manganese‐oxo species that effectively oxidizes tert‐butyl C−H bonds. Leveraging on the interplay of steric, electronic, medium and torsional effects, site‐selective and product chemoselective hydroxylation of the tert‐butyl group is accomplished with broad reaction scope, delivering primary alcohols as largely dominant products in preparative yields. Late‐stage hydroxylation at tert‐butyl sites is demonstrated on 6 densely functionalized molecules of pharmaceutical interest. This work uncovers a novel disconnection approach, harnessing tert‐butyl as a potential functional group in strategic synthetic planning for complex molecular architectures. [ABSTRACT FROM AUTHOR]

The tert‐butyl group is a common aliphatic motif extensively employed to implement steric congestion and conformational rigidity in organic and organometallic molecules. Because of the combination of a high bond dissociation energy (~100 kcal mol−1) and limited accessibility, in the absence of directing groups, neither radical nor organometallic approaches are effective for the chemical modification of tert‐butyl C−H bonds. Herein we overcome these limits by employing a highly electrophilic manganese catalyst, [Mn(CF3bpeb)(OTf)2], that operates in the strong hydrogen bond donor solvent nonafluoro‐tert‐butyl alcohol (NFTBA) and catalytically activates hydrogen peroxide to generate a powerful manganese‐oxo species that effectively oxidizes tert‐butyl C−H bonds. Leveraging on the interplay of steric, electronic, medium and torsional effects, site‐selective and product chemoselective hydroxylation of the tert‐butyl group is accomplished with broad reaction scope, delivering primary alcohols as largely dominant products in preparative yields. Late‐stage hydroxylation at tert‐butyl sites is demonstrated on 6 densely functionalized molecules of pharmaceutical interest. This work uncovers a novel disconnection approach, harnessing tert‐butyl as a potential functional group in strategic synthetic planning for complex molecular architectures. [ABSTRACT FROM AUTHOR]

Adding HClO4 to [(BnTPEN)MnIII–OO]+ in MeOH generates a short-lived MnIII–OOH species, which converts to a putative MnV＝O species. The potent MnV＝O species in MeCN oxidizes the pendant phenyl ring of the ligand in an intramolecular fashion. The addition of benzene causes the formation of (BnTPEN)MnIII-phenolate. These findings suggest that high valent Mn species have the potential to catalyze challenging aromatic hydroxylation reactions. [ABSTRACT FROM AUTHOR]

The aim of this study was to obtain new halolactones with a gem-dimethyl group in the cyclohexane ring (at the C-3 or C-5 carbon) and a methyl group in the lactone ring and then subject them to biotransformations using filamentous fungi. Halolactones in the form of mixtures of two diasteroisomers were subjected to screening biotransformations, which showed that only compounds with a gem-dimethyl group located at the C-5 carbon were transformed. Strains from the genus Fusarium carried out hydrolytic dehalogenation, while strains from the genus Absidia carried out hydroxylation of the C-7 carbon. Both substrates and biotransformation products were then tested for antimicrobial activity against multidrug-resistant strains of both bacteria and yeast-like fungi. The highest antifungal activity against C. dubliniensis and C. albicans strains was obtained for compound 5b, while antimicrobial activity against S. aureus MRSA was obtained for compound 4a. [ABSTRACT FROM AUTHOR]

The 2-pyrone moiety is present in a wide range of structurally diverse natural products with various biological activities. The plant biosynthetic routes towards these compounds mainly depend on the activity of either type III polyketide synthase-like 2-pyrone synthases or hydroxylating 2-oxoglutarate dependent dioxygenases. In the present study, the substrate specificity of these enzymes is investigated by a systematic screening using both natural and artificial substrates with the aims of efficiently forming (new) products and understanding the underlying catalytic mechanisms. In this framework, we focused on the in vitro functional characterization of a 2-pyrone synthase Gh2PS2 from Gerbera x hybrida and two dioxygenases AtF6'H1 and AtF6'H2 from Arabidopsis thaliana using a set of twenty aromatic and aliphatic CoA esters as substrates. UHPLC-ESI-HRMSn based analyses of reaction intermediates and products revealed a broad substrate specificity of the enzymes, enabling the facile "green" synthesis of this important class of natural products and derivatives in a one-step/one-pot reaction in aqueous environment without the need for halogenated or metal reagents and protective groups. Using protein modeling and substrate docking we identified amino acid residues that seem to be important for the observed product scope. • Enzymatic synthesis led to the one-pot formation of 2-pyrones from coenzyme A esters. • Promiscuous polyketide synthases or hydroxylases were applied in the reactions. • The syntheses yielded both natural and new-to-nature 2-pyrones including coumarins. • The formed derivatives constitute lead structures for improved aromas and biocides. [ABSTRACT FROM AUTHOR]

Three types of smectite with various crystallochemical compositions and interlayer cations as well as kaolinite and illite were fired at 800°C and 650°C and tested for their rehydroxylation's (RHX) potential and kinetics in the presence of water vapor at 200°C–350°C. A dehydroxylated structure of 2:1 Al‐rich mineral with the interlayer pillared by a large cation (like K+ or Cs+) is wide enough to allow H2O diffusion which results in advanced RHX, that is, restoring up to several tens of percent of the original OH content. Such 2:1 layer structures (beidellite, illite) do not follow the time‐to‐the‐quarter (TTTQ) kinetics during RHX and show a non‐Arrhenius behavior for isothermal RHX. Because TTTQ kinetics is assumed in an RHX dating of ceramic artifacts in archaeometry, fired‐clay ceramics prepared from material dominated by Al‐rich 2:1 minerals was found unfeasible for RHX dating. Kaolinite and Mg2+‐ or Ca2+‐exchanged smectites show the Arrhenius behavior and follow the TTTQ kinetics of RHX, resulting in apparent Ea increase with the progress of reaction (up to α ∼0.2) of ∼20–50 kJ/mol in beidellite and 15–35 kJ/mol in montmorillonite. We suggest using 'hydroxylation' rather than 'rehydroxylation' for structurally‐disordered fired clays gaining OH groups in an unknown position. [ABSTRACT FROM AUTHOR]

A phytoalexin polyphenolic chemical, resveratrol, can be found in a variety of foods, including cereals, peanuts, grapes, strawberries, and raspberries. It is also known that resveratrol protects the body against cardiovascular diseases as well as various types of cancer. In addition to these health issues, resveratrol is currently the subject of research since it helps treat and prevent a number of illnesses. More clinical research is needed to validate resveratrol's potential as a therapeutic agent, despite the plethora of in vitro and in vivo evidence to support this. When the literature data are evaluated, the fact that resveratrol has a therapeutic effect in these studies, but it is known to be subject to rapid metabolism despite its low bioavailability and oral absorption of approximately 75%, has directed the studies to resveratrol derivatives, especially piceatannol. Based on recent studies, 4 types of resveratrol derivatives were assessed in this work: hydroxylated compounds, methoxylated compounds, glycosides, and oligomers. Because of their advantageous bioactivities, methoxylated, hydroxylated, and halogenated derivatives have drawn the most interest among these classes. However, as a result of these studies, more studies should be conducted to better understand whether resveratrol derivatives can be recommended as therapeutic agents. [ABSTRACT FROM AUTHOR]

The hydroxylation of remote C(sp3)−H bonds in aliphatic amino acids yields crucial precursors for the synthesis of high‐value compounds. However, accurate regulation of the regioselectivity of remote C(sp3)−H bonds hydroxylation in aliphatic amino acids continues to be a common challenge in chemosynthesis and biosynthesis. In this study, the Fe(II)/α‐ketoglutarate‐dependent dioxygenase from Bacillus subtilis (BlAH) was mined and found to catalyze hydroxylation at the γ and δ sites of aliphatic amino acids. Crystal structure analysis, molecular dynamics simulations, and quantum chemical calculations revealed that regioselectivity was regulated by the spatial effect of BlAH. Based on these results, the spatial effect of BlAH was reconstructed to stabilize the transition state at the δ site of aliphatic amino acids, thereby successfully reversing the γ site regioselectivity to the δ site. For example, the regioselectivity of L‐Homoleucine (5 a) was reversed from the γ site (1 : 12) to the δ site (>99 : 1). The present study not only expands the toolbox of biocatalysts for the regioselective functionalization of remote C(sp3)−H bonds, but also provides a theoretical guidance for the precision‐driven modification of similarly remote C(sp3)−H bonds in complex molecules. [ABSTRACT FROM AUTHOR]

Lytic polysaccharide monooxygenases (LPMOs) are Cu‐dependent metalloenzymes that catalyze the hydroxylation of strong C−H bonds in polysaccharides using O2 or H2O2 as oxidants (monooxygenase/peroxygenase). In the absence of C−H substrate, LPMOs reduce O2 to H2O2 (oxidase) and H2O2 to H2O (peroxidase) using proton/electron donors. This rich oxidative reactivity is promoted by a mononuclear Cu center in which some of the amino acid residues surrounding the metal might accept and donate protons and/or electrons during O2 and H2O2 reduction. Herein, we utilize a podal ligand containing H‐bond/proton donors (LH2) to analyze the reactivity of mononuclear Cu species towards O2 and H2O2. [(LH2)CuI]1+ (1), [(LH2)CuII]2+ (2), [(LH−)CuII]1+ (3), [(LH2)CuII(OH)]1+ (4), and [(LH2)CuII(OOH)]1+ (5) were synthesized and characterized by structural and spectroscopic means. Complex 1 reacts with O2 to produce 5, which releases H2O2 to generate 3, suggesting that O2 is used by LPMOs to generate H2O2. The reaction of 1 with H2O2 produces 4 and hydroxyl radical, which reacts with C−H substrates in a Fenton‐like fashion. Complex 3, which can generate 1 via a reversible protonation/reduction, binds H2O and H2O2 to produce 4 and 5, respectively, a mechanism that could be used by LPMOs to control oxidative reactivity. [ABSTRACT FROM AUTHOR]

Herein, a new method has been developed for the synthesis of various α‐hydroxyacetophenones via an electro‐oxidation process. It involves electrocatalytic hydroxylation via debromination of C(sp3)−Br bond. Here, simultaneous breaking of carbon‐bromine (C−Br) bond and formation of a new carbon‐oxygen (C−O) bond has been achieved through electrolysis of H2O using binary mixture of water and DMSO. The protocol features easy performance, oxidant and base‐free mild conditions and short reaction time. [ABSTRACT FROM AUTHOR]

Crafting single‐atom catalysts (SACs) that possess "just right" modulated electronic and geometric structures, granting accessible active sites for direct room‐temperature benzene oxidation is a coveted objective. However, achieving this goal remains a formidable challenge. Here, we introduce an innovative in situ phosphorus‐immitting strategy using a new phosphorus source (phosphorus nitride, P3N5) to construct the phosphorus‐rich copper (Cu) SACs, designated as Cu/NPC. These catalysts feature locally protruding metal sites on a nitrogen (N)‐phosphorus (P)‐carbon (C) support (NPC). Rigorous analyses, including X‐ray absorption spectroscopy (XAS) and X‐ray photoelectron spectroscopy (XPS), validate the coordinated bonding of nitrogen and phosphorus with atomically dispersed Cu sites on NPC. Crucially, systematic first‐principles calculations, coupled with the climbing image nudged‐elastic‐band (CI‐NEB) method, provide a comprehensive understanding of the structure‐property‐activity relationship of the distorted Cu−N2P2 centers in Cu/NPC for selective oxidation of benzene to phenol production. Interestingly, Cu/NPC has shown more energetically favorable C−H bond activation compared to the benchmark Cu/NC SACs in the direct oxidation of benzene, resulting in outstanding benzene conversion (50.3 %) and phenol selectivity (99.3 %) at room temperature. Furthermore, Cu/NPC achieves a remarkable turnover frequency of 263 h−1 and mass‐specific activity of 35.2 mmol g−1 h−1, surpassing the state‐of‐the‐art benzene‐to‐phenol conversion catalysts to date. [ABSTRACT FROM AUTHOR]

Crafting single‐atom catalysts (SACs) that possess "just right" modulated electronic and geometric structures, granting accessible active sites for direct room‐temperature benzene oxidation is a coveted objective. However, achieving this goal remains a formidable challenge. Here, we introduce an innovative in situ phosphorus‐immitting strategy using a new phosphorus source (phosphorus nitride, P3N5) to construct the phosphorus‐rich copper (Cu) SACs, designated as Cu/NPC. These catalysts feature locally protruding metal sites on a nitrogen (N)‐phosphorus (P)‐carbon (C) support (NPC). Rigorous analyses, including X‐ray absorption spectroscopy (XAS) and X‐ray photoelectron spectroscopy (XPS), validate the coordinated bonding of nitrogen and phosphorus with atomically dispersed Cu sites on NPC. Crucially, systematic first‐principles calculations, coupled with the climbing image nudged‐elastic‐band (CI‐NEB) method, provide a comprehensive understanding of the structure‐property‐activity relationship of the distorted Cu−N2P2 centers in Cu/NPC for selective oxidation of benzene to phenol production. Interestingly, Cu/NPC has shown more energetically favorable C−H bond activation compared to the benchmark Cu/NC SACs in the direct oxidation of benzene, resulting in outstanding benzene conversion (50.3 %) and phenol selectivity (99.3 %) at room temperature. Furthermore, Cu/NPC achieves a remarkable turnover frequency of 263 h−1 and mass‐specific activity of 35.2 mmol g−1 h−1, surpassing the state‐of‐the‐art benzene‐to‐phenol conversion catalysts to date. [ABSTRACT FROM AUTHOR]

Metal oxoclusters constitute a dynamic and expanding domain of research with versatile applications in catalysis, materials science, medicine, and beyond. Particular attention has been given to their potential utility due to their distinctive properties. The incorporation of ionic liquid (IL) environments into metal oxocluster (MOC) systems offers numerous advantages, including higher stability, tunable coordination to metal sites, and the capability to dissolve diverse substrates for catalytic applications. Although IL-stabilized MOCs (IL--MOCs) are still in the developmental phase, their potential to revolutionize catalysis is substantial. As research progresses, IL--MOCs will likely play an increasingly important role in catalysis. This perspective article focuses on the preparation methods of IL--MOCs, how the MOCs are stabilized/regulated by ILs or even PIL (polymeric ILs), as well as their catalytic applications, including oxidation, epoxidation, oxidative desulfurization, biomass oxidation, hydroxylation of benzene, acid catalysis, CO2 activation and utilization, carbonylation, hydrogenation/hydrolysis, electrochemistry, etc. IL--MOCs have played a crucial role in the development of sustainable chemistry in the light of the potential opportunities and challenges. The unique advantages make IL--MOCs outstanding candidates for industrial catalysts. [ABSTRACT FROM AUTHOR]

Key message: Mutants lacking functional HYD2 homoeologs showed improved seedling growth, but comparable or increased susceptibility to salt stress in tillering plants, suggesting a developmentally restricted role of HYD2 in salt response. Salinity stress threatens global food security by reducing the yield of staple crops such as wheat (Triticum ssp.). Understanding how wheat responds to salinity stress is crucial for developing climate resilient varieties. In this study, we examined the interplay between carotenoid metabolism and the response to salt (NaCl) stress, a specific form of salinity stress, in tetraploid wheat plants with mutations in carotenoid β-hydroxylase 1 (HYD1) and HYD2. Our investigation encompassed both the vulnerable seedling stage and the more developed tillering stage of wheat plant growth. Mutant combinations lacking functional HYD2 homoeologs, including hyd-A2 hyd-B2, hyd-A1 hyd-A2 hyd-B2, hyd-B1 hyd-A2 hyd-B2, and hyd-A1 hyd-B1 hyd-A2 hyd-B2, had longer first true leaves and slightly enhanced root growth during germination under salt stress compared to the segregate wild-type (control) plants. Interestingly, these mutant seedlings also showed decreased levels of neoxanthin and violaxanthin (xanthophylls derived from β-carotene) and an increase in β-carotene in roots. However, tillering hyd mutant and segregate wild-type plants generally did not differ in their height, tiller count, and biomass production under acute or prolonged salt stress, except for decreases in these parameters observed in the hyd-A1 hyd-B1 hyd-A2 hyd-B2 mutant that indicate its heightened susceptibility to salt stress. Taken together, these findings suggest a significant, yet developmentally restricted role of HYD2 homoeologs in salt-stress response in tetraploid wheat. They also show that hyd-A2 hyd-B2 mutant plants, previously demonstrated for possessing enriched nutritional (β-carotene) content, maintain an unimpaired ability to withstand salt stress. [ABSTRACT FROM AUTHOR]

Chiral methyl mandelates are useful synthons in organic transformation and pharmaceutical synthesis. Green synthesis of these valuable compounds by direct C–H activating oxidative hydroxylation has attracted keen interest. Described herein is achieving the stereoselective and efficient bio-hydroxylation of methyl 2-phenylacetates to the chiral methyl mandelates by directed evolution of the cytochrome P450DA hydroxylase. In the present study, a new colorimetric high-throughput screening assay was successfully developed based on a dualenzyme cascade for the engineering of the P450DA's hydroxylation activity. Several beneficial variants with enhanced bio-hydroxylation activity were created by combining random mutagenesis and site-saturated/directed mutagenesis strategies. Whole-cell bio-hydroxylation of various methyl 2-phenylacetates using the best septupletmutant P450DA-11 yielded the corresponding chiral methyl mandelates in up to 92% isolated yields and >99% ee. [ABSTRACT FROM AUTHOR]

Manganese (Mn) oxides are promising cathode materials for rechargeable aqueous Zn‐ion batteries. However, the Mn dissolution in weakly acidic electrolytes always hinders the development of better aqueous Zn–Mn batteries. Herein, a hydroxylated manganese oxide cathode material (H‐MnO2) is fabricated using an electrochemical method for stable aqueous Zn–Mn batteries without relying on the Mn2+ electrolyte additives. The partial hydroxylation of the oxides leads to charge redistribution of the material, changing the reaction thermodynamics and kinetics. Theoretical simulation suggests that the hydroxylation of manganese oxide promotes both Zn2+ adsorption thermodynamics and diffusion kinetics on the surface of H‐MnO2 but weakens the interaction between H+ and the electrode. Therefore, Zn2+ ions can be more reactive with the hydroxylated manganese oxide than H+ ions. Experimental results show that the Zn2+ insertion mechanism dominates the charge storage process of H‐MnO2, and the H+‐induced Mn dissolution reaction is effectively alleviated. Importantly, H‐MnO2 exhibits good cycling stability with 95% capacity retention over 5000 cycles at the current density of 3.8 A g−1 in the ZnSO4 electrolyte, outperforming the state‐of‐the‐art aqueous Zn–Mn batteries, even those with Mn2+ electrolyte additives. The findings provide new insights for designing stable manganese oxide cathodes in aqueous Zn–Mn batteries. [ABSTRACT FROM AUTHOR]

Comprehensive Summary The development of catalytic asymmetric methods that enable access to value‐added functionalities or structures, exemplified by allylic alcohols, is a highly interesting yet challenging topic from both academic and industrial perspectives. However, before recent advances in chemical catalysis, there were scarce protocols toward constructing enantioenriched tertiary allylic alcohol scaffolds. In this context, peptide‐mimic phosphonium salts were found to be highly efficient in catalytic asymmetric α‐hydroxylation of α,β‐unsaturated and/or β,ϒ‐unsaturated compounds with satisfactory regio‐ and stereochemical outcomes (up to 97% yield and 95% ee). This methodology tolerates a broad array of substrates and thus provides an expeditious and unified platform for the assembly of enantioenriched tertiary allylic alcohols by avoiding the use of additional reductants and expensive metal catalysts. Furthermore, the power of this protocol is enlarged by simple conditions and the use of air as a source of hydroxyl functionality. [ABSTRACT FROM AUTHOR]

Selective, one‐step C−H activation of fatty acids from biomass is an attractive concept in sustainable chemistry. Biocatalysis has shown promise for generating high‐value hydroxy acids, but to date enzyme discovery has relied on laborious screening and produced limited hits, which predominantly oxidise the subterminal positions of fatty acids. Herein we show that ancestral sequence reconstruction (ASR) is an effective tool to explore the sequence‐activity landscape of a family of multidomain, self‐sufficient P450 monooxygenases. We resurrected 11 catalytically active CYP116B ancestors, each with a unique regioselectivity fingerprint that varied from subterminal in the older ancestors to mid‐chain in the lineage leading to the extant, P450‐TT. In lineages leading to extant enzymes in thermophiles, thermostability increased from ancestral to extant forms, as expected if thermophily had arisen de novo. Our studies show that ASR can be applied to multidomain enzymes to develop active, self‐sufficient monooxygenases as regioselective biocatalysts for fatty acid hydroxylation. [ABSTRACT FROM AUTHOR]

Selective, one‐step C−H activation of fatty acids from biomass is an attractive concept in sustainable chemistry. Biocatalysis has shown promise for generating high‐value hydroxy acids, but to date enzyme discovery has relied on laborious screening and produced limited hits, which predominantly oxidise the subterminal positions of fatty acids. Herein we show that ancestral sequence reconstruction (ASR) is an effective tool to explore the sequence‐activity landscape of a family of multidomain, self‐sufficient P450 monooxygenases. We resurrected 11 catalytically active CYP116B ancestors, each with a unique regioselectivity fingerprint that varied from subterminal in the older ancestors to mid‐chain in the lineage leading to the extant, P450‐TT. In lineages leading to extant enzymes in thermophiles, thermostability increased from ancestral to extant forms, as expected if thermophily had arisen de novo. Our studies show that ASR can be applied to multidomain enzymes to develop active, self‐sufficient monooxygenases as regioselective biocatalysts for fatty acid hydroxylation. [ABSTRACT FROM AUTHOR]

Adherent bubbles at electrodes are generally treated as reaction penalties. Herein, in situ hydroxylation of indium tin oxide surfaces can be easily achieved by applying a constant potential of +1.0 V in the presence of bubbles. Its successful hydroxylation is further demonstrated by preparing a ferrocene-terminated film, which is confirmed by cyclic voltammetry and X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Ga2O3 is an ultra‐wide‐bandgap semiconductor that is receiving considerable attention due to its promising applications in high‐frequency, high‐power and high‐temperature settings. It can be prepared by calcinating the α‐GaOOH phase at high temperatures. Understanding the significance of hydroxyl groups in α‐GaOOH, dehydroxylation and the structural transition at high temperatures has become a key aspect of preparing high‐quality α‐Ga2O3 crystals, but the underlying mechanism remains unknown. In this research, α‐GaOOH nanorods were hydrothermally synthesized and the structural evolution of α‐GaOOH investigated at high temperatures by in situ X‐ray diffraction. The hydroxyl group in α‐GaOOH squeezes Ga3+ from the center of the [GaO6] octahedron, resulting in deformed [GaO6] octahedra and significant microstrain in α‐GaOOH. The hydroxyl groups are peeled off from α‐GaOOH when the temperature exceeds 200°C, resulting in contraction along the c‐axis direction and expansion along the a‐axis direction of α‐GaOOH. When the temperature exceeds 300°C, the Ga—O bond inside the double chains preferentially breaks to generate square‐wave‐like octahedron chains, and the neighboring chains repack to form hexagonal‐like octahedron layers. The octahedron layers are packed up and down by electrostatic interaction to generate the α‐Ga2O3 structure. This work highlights the role of hydroxyl groups in α‐GaOOH, dehydroxylation and the structural transition on the atomic scale, providing valuable guidelines for the fabrication of high‐quality α‐Ga2O3 crystals. [ABSTRACT FROM AUTHOR]

A facile solvent casting technique has been reported in the fabrication of surface hydroxylated ZnFe2O4 (h‐ZFO) nanoparticles (NPs) filled with poly(vinylidene fluoride) (PVDF) as a matrix. The h‐ZFO filler particles are synthesized from neat ZnFe2O4. The dielectric and electric performance of polymer‐based composites is much related to the interface binding between filler particles and polymer matrix. In this work, the surface alternation technique employed a new path is developed to improve the compatibility between ZFO particles and the PVDF matrix. These PVDF‐ZFO composites were studied by X‐ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The h‐ZFO‐PVDF and ZFO‐PVDF composites are carefully analyzed by dielectric and electric properties by a wide range of frequencies. However, the morphological analysis exhibits uniform dispersion of the h‐ZFO NPs in the PVDF matrix. The h‐ZFO‐PVDF composites have a dielectric constant of about 35 for 1.5 wt.% of filler contents. Moreover, the h‐ZFO‐PVDF composites have lower dielectric loss than PVDF‐ZFO composites. It is suggested that the strong interaction between h‐ZFO filler particles and the PVDF matrix is the main reason for the improvement of dielectric properties. The outcomes of these methods have great potential for making high dielectric constants and relatively suppressed loss PVDF‐ZFO composites for advanced practical applications. [ABSTRACT FROM AUTHOR]

Steroids with hydroxylation at C14 are drawing increased attention because of their diverse biological activities and applications. P-450lun from Cochliobolus lunatus is the first fungal cytochrome P450 reported to have 14α-hydroxylase activity. Studies have shown that P-450lun catalyzes the hydroxylation of progesterone (PROG) at C14α with low regiospecificity and activity. To improve its regiospecificity and activity for PROG, truncated forms of P-450lun and its cognate redox partner CPRlun were functionally co-expressed in Escherichia coli. Then, a semi-rational protein engineering approach was applied to P-450lun, resulting in a double-site mutant E109A/F297W with enhanced 14α-position selectivity for PROG compared with the wild-type P-450lun (97% vs. 28%). Protein structure analysis revealed that the F297W substitution can hinder the binding pose for 11β-hydroxylation product formation. Finally, whole-cell catalysis was optimized, and the final titer of 14α-OH-PROG reached 16.0 mg/L. This is the first report where a fungal 14α-hydroxylase was functionally expressed in Escherichia coli. The steroid hydroxylation system obtained in this study can serve as a basis for the synthesis of 14α-hydroxylated PROG and the rapid evolution of eukaryotic cytochrome P-450lun. [ABSTRACT FROM AUTHOR]

Aim: Bile acids are suggested to be involved in the antidiarrhetic effect of Goreisan (GRS). This study aimed to investigate the effect of GRS on fecal bile acid levels and composition of the gut microbiota in mice. Correlation analysis was employed to identify the potential gut microbiota associated with the alterations in fecal bile acid levels induced by GRS. Methods: Male C57BL/6 mice were fed a diet supplemented with GRS water extract for 4 weeks. Feces and cecal contents were collected from the mice to determine bile acid levels and analyze bacterial composition. Results: GRS administration significantly increased the levels of fecal secondary bile acids, including ω‐muricholic acid (MCA), hyodeoxycholic acid (HDCA), and lithocholic acid (LCA). In contrast, the levels of primary bile acids, such as β‐MCA, cholic acid (CA), and chenodeoxycholic acid (CDCA) showed a marked decrease. Further analysis revealed a positive correlation between the relative abundance of Alloprevotella, Dehalobacterium PAC001221, and Eubacterium g23 and fecal levels of ωMCA, HDCA, and LCA. Conclusions: GRS was suggested to promote the formation of fecal secondary bile acids in mice, possibly through the enhancement of bacterial 7β‐dehydroxylation and 6β‐epimerization activities. These changes may be involved in the antidiarrhetic action of GRS. Concurrent evaluation of fecal bile acids and gut microbiota presents a promising approach for elucidating the novel mechanisms underlying the effects of kampo formulations, particularly in modulating the microbial metabolism of intestinal bile acids. [ABSTRACT FROM AUTHOR]

The diversity and uniqueness of fungal cytochromes P450 (CYP), capable of catalyzing the regio- and stereospecific hydroxylation of steroids, makes them important for microbiological synthesis of valuable hydroxysteroids. In the present work, the function of recombinant fungal P450 monooxygenase (CYPI) of Curvularia sp. strain VKM F-3040, a promising biocatalyst of 7-hydroxylation of androstane steroids, was studied. RT-PCR amplification of cDNA of the candidate genes encoding CYPI and its natural redox partner (POR), their cloning and heterologous expression in the cells of E. coli BL 21 DE(3) was carried out. In vitro experiments showed the ability of the obtained recombinant monooxygenase to catalyze hydroxylation of dehydroepiandrosterone (DHEA) at positions 7α and 7β. Our results expand the knowledge about fungal steroid hydroxylases and open up the prospects for the synthesis of valuable 7-hydroxysteroids by using recombinant producers. [ABSTRACT FROM AUTHOR]

All biological hydroxylation reactions are thought to derive the oxygen atom from one of three inorganic oxygen donors, O2, H2O2 or H2O. Here, we have identified the organic compound prephenate as the oxygen donor for the three hydroxylation steps of the O2-independent biosynthetic pathway of ubiquinone, a widely distributed lipid coenzyme. Prephenate is an intermediate in the aromatic amino acid pathway and genetic experiments showed that it is essential for ubiquinone biosynthesis in Escherichia coli under anaerobic conditions. Metabolic labeling experiments with 18O-shikimate, a precursor of prephenate, demonstrated the incorporation of 18O atoms into ubiquinone. The role of specific iron--sulfur enzymes belonging to the widespread U32 protein family is discussed. Prephenate-dependent hydroxylation reactions represent a unique biochemical strategy for adaptation to anaerobic environments. [ABSTRACT FROM AUTHOR]

Saxitoxin (STX, 1) is a representative compound of paralytic shellfish toxins (PSTs) that are produced by marine dinoflagellates and freshwater cyanobacteria. Although several pathways have been proposed for the biosynthesis of STX, the order of ring and side chain hydroxylation, and formation of the tricyclic skeleton have not been well established. In this study, 12,12‐dideoxy‐decarbamoyloxySTX (dd‐doSTX, 2), the most reduced STX analogue having the tricyclic skeleton, and its analogues, 12β‐deoxy‐doSTX (12β‐d‐doSTX, 3), 12α‐deoxy‐doSTX (12α‐d‐doSTX, 4), and doSTX (5), were synthesized, and these compounds were screened in the toxic microalgae using high‐resolution LCMSMS. dd‐doSTX (2) and 12β‐d‐doSTX (3) were identified in the PSTs‐producing dinoflagellates (Alexandrium catenella, A. pacificum, and/or Gymnodinium catenatum) and in the cyanobacterium Dolichospermum circinale (TA04). doSTX (5), previously isolated from the dinoflagellate G. catenatum, was also identified in D. circinale (TA04). Furthermore, the conversion of 2 to 3, and 4 to 5, by SxtT with VanB, a reported Rieske oxygenase and its redox partner in STX biosynthesis, was confirmed. These results support that 2 is a possible biosynthetic precursor of STX, and that ring and side‐chain hydroxylations proceed after cyclization. [ABSTRACT FROM AUTHOR]

Biocatalytic oxidations are an emerging technology for selective C−H bond activation. While promising for a range of selective oxidations, practical use of enzymes catalyzing aerobic hydroxylation is presently limited by their substrate scope and stability under industrially relevant conditions. Here, we report the engineering and practical application of a non‐heme iron and α‐ketoglutarate‐dependent dioxygenase for the direct stereo‐ and regio‐selective hydroxylation of a non‐native fluoroindanone en route to the oncology treatment belzutifan, replacing a five‐step chemical synthesis with a direct enantioselective hydroxylation. Mechanistic studies indicated that formation of the desired product was limited by enzyme stability and product overoxidation, with these properties subsequently improved by directed evolution, yielding a biocatalyst capable of >15,000 total turnovers. Highlighting the industrial utility of this biocatalyst, the high‐yielding, green, and efficient oxidation was demonstrated at kilogram scale for the synthesis of belzutifan. [ABSTRACT FROM AUTHOR]

Biocatalytic oxidations are an emerging technology for selective C−H bond activation. While promising for a range of selective oxidations, practical use of enzymes catalyzing aerobic hydroxylation is presently limited by their substrate scope and stability under industrially relevant conditions. Here, we report the engineering and practical application of a non‐heme iron and α‐ketoglutarate‐dependent dioxygenase for the direct stereo‐ and regio‐selective hydroxylation of a non‐native fluoroindanone en route to the oncology treatment belzutifan, replacing a five‐step chemical synthesis with a direct enantioselective hydroxylation. Mechanistic studies indicated that formation of the desired product was limited by enzyme stability and product overoxidation, with these properties subsequently improved by directed evolution, yielding a biocatalyst capable of >15,000 total turnovers. Highlighting the industrial utility of this biocatalyst, the high‐yielding, green, and efficient oxidation was demonstrated at kilogram scale for the synthesis of belzutifan. [ABSTRACT FROM AUTHOR]

Inspired by the ubiquitous prevalence of 3‐hydroxyoxindoles in natural products and pharmaceuticals, we herein disclose a direct and practical transition‐metal‐free asymmetric hydroxylation using commercially available Davis enantiopure oxaziridines as efficient oxidants, expeditiously affording an array of medicinally active 3‐functionalized 3‐hydroxy‐2‐oxindoles bearing quaternary stereocenters. The protocol features cheap reactants, ease of operation, scalability, and good functional‐group tolerance and efficient formal synthesis of natural products. [ABSTRACT FROM AUTHOR]

The Von Hippel–Lindau (VHL) protein, which is frequently mutated in clear-cell renal cell carcinoma (ccRCC), is a master regulator of hypoxia-inducible factor (HIF) that is involved in oxidative stresses. However, whether VHL possesses HIF-independent tumor-suppressing activity remains largely unclear. Here, we demonstrate that VHL suppresses nutrient stress-induced autophagy, and its deficiency in sporadic ccRCC specimens is linked to substantially elevated levels of autophagy and correlates with poorer patient prognosis. Mechanistically, VHL directly binds to the autophagy regulator Beclin1, after its PHD1-mediated hydroxylation on Pro54. This binding inhibits the association of Beclin1-VPS34 complexes with ATG14L, thereby inhibiting autophagy initiation in response to nutrient deficiency. Expression of non-hydroxylatable Beclin1 P54A abrogates VHL-mediated autophagy inhibition and significantly reduces the tumor-suppressing effect of VHL. In addition, Beclin1 P54-OH levels are inversely correlated with autophagy levels in wild-type VHL-expressing human ccRCC specimens, and with poor patient prognosis. Furthermore, combined treatment of VHL-deficient mouse tumors with autophagy inhibitors and HIF2α inhibitors suppresses tumor growth. These findings reveal an unexpected mechanism by which VHL suppresses tumor growth, and suggest a potential treatment for ccRCC through combined inhibition of both autophagy and HIF2α. Synopsis: PHD1-mediated prolyl hydroxylation targets HIF-1α for VHL-dependent ubiquitination and is a key step in the cell's oxygen sensing machinery. This work shows that PHD1 and VHL also inhibit Beclin1 and autophagy initiation, with dysregulation leading to clear-cell renal cell carcinoma progression. PHD1 mediates Beclin1 Pro54 hydroxylation on pre-autophagosomal structures in clear-cell renal cell carcinoma cells. VHL binds to Pro54-hydroxylated Beclin1 and prevents the association between ATG14L and Beclin1/VPS34. VHL inhibits VPS34-dependent PI(3)P production, autophagy initiation, and kidney tumor growth. The Von Hippel-Lindau (VHL) E3 ligase binds to proline-hydroxylated Beclin1, inhibiting the initiation of autophagy and blocking kidney tumor growth. [ABSTRACT FROM AUTHOR]

SznF, a member of the emerging family of heme‐oxygenase‐like (HO‐like) di‐iron oxidases and oxygenases, employs two distinct domains to catalyze the conversion of Nω‐methyl‐L‐arginine (L‐NMA) into N‐nitroso‐containing product, which can subsequently be transformed into streptozotocin. Using unrestricted density functional theory (UDFT) with the hybrid functional B3LYP, we have mechanistically investigated the two sequential hydroxylations of L‐NMA catalyzed by SznF's binuclear iron central domain. Mechanism B primarily involves the O−O bond dissociation, forming Fe(IV)=O, induced by the H+/e− introduction to the FeA side of μ‐1,2‐peroxo‐Fe2(III/III), the substrate hydrogen abstraction by Fe(IV)=O, and the hydroxyl rebound to the substrate N radical. The stochastic addition of H+/e− to the FeB side (mechanism C) can transition to mechanism B, thereby preventing enzyme deactivation. Two other competing mechanisms, involving the direct O−O bond dissociation (mechanism A) and the addition of H2O as a co‐substrate (mechanism D), have been ruled out. [ABSTRACT FROM AUTHOR]

The Cu−O−Cu core has been proposed as a potential site for methane oxidation in particulate methane monooxygenase. In this work, we used density functional theory (DFT) to design a mixed‐valent CuIII−O−CuII species from an experimentally known peroxo‐dicopper complex supported by N‐donor ligands containing phenolic groups. We found that the transfer of two‐protons and two‐electrons from phenolic groups to peroxo‐dicopper core takes place, which results to the formation of a bis‐μ‐hydroxo‐dicopper core. The bis‐μ‐hydroxo‐dicopper core converts to a mixed‐valent CuIII−O−CuII core with the removal of a water molecule. The orbital and spin density analyses unravel the mixed‐valent nature of CuIII−O−CuII. We further investigated the reactivity of this mixed‐valent core for aliphatic C−H hydroxylation. Our study unveiled that mixed‐valent CuIII−O−CuII core follows a hydrogen atom transfer mechanism for C−H activation. An in‐situ generated water molecule plays an important role in C−H hydroxylation by acting as a proton transfer bridge between carbon and oxygen. Furthermore, to assess the relevance of a mixed‐valent CuIII−O−CuII core, we investigated aliphatic C−H activation by a symmetrical CuII−O−CuII core. DFT results show that the mixed‐valent CuIII−O−CuII core is more reactive toward the C−H bond than the symmetrical CuII−O−CuII core. [ABSTRACT FROM AUTHOR]

The purpose of this article is to provide a study of the hydroxylation reaction optimization of epoxidized soybean oil using a mathematical model based on surface response methodology. The variables were selected based on previous studies of the reaction. The three most influential factors are the time, the methanol ratio, and the catalyst ratio. Potentiometric characterization of the hydroxyl index allowed the influence of these factors and their interactions to be measured. It was possible to quantify these influences using multivariate regression. The results show that the three selected factors influenced the reaction yield positively; however, there were some interactions, such as an interaction between time and methanol and the interaction between time and catalyst, which had a negligible influence. The coefficients of the formulas used to construct the mathematical model were obtained from the influence values. The model was able to predict the optimum variable levels for an acceptable reaction yield efficiently and accurately. These levels were: time 244.4 min; methanol:oil ratio 1:4, and catalyst percentage 15.34%. The characterization of the hydroxylated oil product was carried out using Fourier‐transform infrared (FTIR) spectroscopy proton nuclear magnetic resonance (1H‐NMR) and carbon‐13 nuclear magnetic resonance (13C‐NMR) spectroscopy. [ABSTRACT FROM AUTHOR]

In this work, the synthesis and characterization of a heterogeneous photocatalyst based on spherical silica nanoparticles superficially modified with anthraquinone 2‐carboxylic acid (AQ−COOH) are presented. The nanomaterial was characterized by TEM, SEM, FT‐IR, diffuse reflectance, fluorescence, NMR, DLS, XRD and XPS. These analyses confirm the covalent linking of AQ−COOH with the NH2 functionality in the nanomaterial and, more importantly, the photocatalyst retains its photophysical properties once bound. The heterogeneous photocatalyst was successfully employed in the aerobic hydroxylation of arylboronic acids to phenols under sustainable reaction conditions. Phenols were obtained in high yields (up to 100 %) with low catalyst loading (3.5 mol %), reaching TOF values of 3.7 h−1. Using 2‐propanol as solvent at room temperature, the visible light photocatalysis produced H2O2 as a key intermediate to promote the aerobic hydroxylation of arylboronic acids. The heterogeneous photocatalyst was reused at least 5 times, without modification of the nanomaterial structure and morphology. This simple heterogeneous system showed great catalytic activity under sustainable reaction conditions. [ABSTRACT FROM AUTHOR]

Flavoprotein monooxygenases catalyze reactions, including hydroxylation and epoxidation, involved in the catabolism, detoxification, and biosynthesis of natural substrates and industrial contaminants. Among them, the 6-hydroxy-3-succinoyl-pyridine (HSP) monooxygenase (HspB) from Pseudomonas putida S16 facilitates the hydroxylation and C-C bond cleavage of the pyridine ring in nicotine. However, the mechanism for biodegradation remains elusive. Here, we refined the crystal structure of HspB and elucidated the detailed mechanism behind the oxidative hydroxylation and C-C cleavage processes. Leveraging structural information about domains for binding the cofactor flavin adenine dinucleotide (FAD) and HSP substrate, we used molecular dynamics simulations and quantum/molecular mechanics calculations to demonstrate that the transfer of an oxygen atom from the reactive FAD peroxide species (C4a-hydroperoxyflavin) to the C3 atom in the HSP substrate constitutes a rate-limiting step, with a calculated reaction barrier of about 20 kcal/mol. Subsequently, the hydrogen atom was rebounded to the FAD cofactor, forming C4a-hydroxyflavin. The residue Cys218 then catalyzed the subsequent hydrolytic process of C-C cleavage. Our findings contribute to a deeper understanding of the versatile functions of flavoproteins in the natural transformation of pyridine and HspB in nicotine degradation.IMPORTANCE Pseudomonas putida S16 plays a pivotal role in degrading nicotine, a toxic pyridine derivative that poses significant environmental challenges. This study highlights a key enzyme, HspB (6-hydroxy-3-succinoyl-pyridine monooxygenase), in breaking down nicotine through the pyrrolidine pathway. Utilizing dioxygen and a flavin adenine dinucleotide cofactor, HspB hydroxylates and cleaves the substrate’s side chain. Structural analysis of the refined HspB crystal structure, combined with state-ofthe- art computations, reveals its distinctive mechanism. The crucial function of Cys218 was never discovered in its homologous enzymes. Our findings not only deepen our understanding of bacterial nicotine degradation but also open avenues for applications in both environmental cleanup and pharmaceutical development. [ABSTRACT FROM AUTHOR]

Site‐selective C(sp3)−H functionalization of unreactive hydrocarbons is always challenging due to its inherited chemical inertness, slightly different reactivity of various C−H bonds, and intrinsically high bond dissociation energies. Here, a site‐selective C−H alkylation of naphthoquinone with unactivated hydrocarbons using Mn2(CO)10 as a catalyst under blue‐light (457 nm) irradiation without any external acid or base and pre‐functionalization is presented. The selective C−H functionalization of tertiary over secondary and secondary over primary C(sp3)−H bonds in abundant chemical feedstocks was achieved, and hydroxylation of quinones was realized in situ by employing the developed methodology. This protocol provides a new catalytic system for the direct construction of high‐value‐added compounds, namely, parvaquone (a commercially available drug used to treat theileriosis) and its derivatives under ambient reaction conditions. Moreover, this operationally simple protocol applies to various linear‐, branched‐, and cyclo‐alkanes with high degrees of site selectivity under blue‐light irradiated conditions and could provide rapid and straightforward access to versatile methodologies for upgrading feedstock chemicals. Mechanistic insight by radical trapping, radical scavenging, EPR, and other controlled experiments well corroborated with DFT studies suggest that the reaction proceeds by a radical pathway. [ABSTRACT FROM AUTHOR]

The development of photocatalysts that are effective in different organic processes is a topic of great interest to researchers in materials chemistry. Herein, we report the design and synthesis of a new covalent triazine framework (CTF) built by acid-catalyzed trimerization of 4,4′-(benzo[b]benzo[4,5]thieno[2,3-d]thiophene-2,7-diyl)dibenzonitrile activated by microwaves that generates a new organic polymer, DPhBTBT-CTF. This CTF exhibits visible-light absorption due to the electron-donating BTBT units and the extended π-conjugated framework with the electron-acceptor triazine node and proves to be an efficient and versatile metal-free heterogeneous photocatalyst for different organic processes such as selective oxidations of both sulfides and benzyl alcohols to sulfoxides and benzaldehydes, respectively or the oxidative bromination of electron rich aromatic compounds. Moreover, two different proof of concept reactions were tested: the Diels–Alder cycloaddition and the hydroxylation of boronic acids. Heterogeneity studies confirmed that this photocatalyst can be recycled without significant loss of selectivity, and also some mechanistic tests suggested the preferred oxidation pathway. [ABSTRACT FROM AUTHOR]

Hydroxylation of aryl sulfonium salts could be realized by utilizing acetohydroxamic acid and oxime as hydroxylative agents in the presence of cesium carbonate as a base, leading to a variety of structurally diverse hydroxylated arenes in 47–95% yields. In addition, the reaction exhibited broad functionality tolerance, and a range of important functional groups (e.g., cyano, nitro, sulfonyl, formyl, keto, and ester) could be well amenable to the mild reaction conditions. [ABSTRACT FROM AUTHOR]

In the present work, we report a neutral dinuclear copper(II) complex, [Cu2(L1)(OH)], derived from a new [N,O] donor Schiff base ligand L1 that was formed after the endogenous hydroxylation of an initial carbamate Schiff base H2L coordinated with copper ions in an electrochemical cell. The copper(II) complex has been fully characterized using different techniques, including X-ray diffraction. Direct current (DC) magnetic susceptibility measurements were also performed at variable temperatures, showing evidence of antiferromagnetic behavior. Its catalase-like activity was also tested, demonstrating that this activity is affected by temperature. [ABSTRACT FROM AUTHOR]

Reported herein is an efficient and eco-friendly peri-selective monohydroxylation of naphthalene monoimides (NMIs) to access 4-hydroxy NMIs, which possess multidisciplinary applications. The key aspect of this method is the utilization of cobalt(II)-catalysis via a single electron transfer mechanism to achieve site-selective C(sp2)-hydroxylation. Transformation of the hydroxyl group into pseudohalides reveals its applications towards cross-coupling reactions. [ABSTRACT FROM AUTHOR]

In the early stages of drug discovery, adequate evaluation of the potential drug–drug interactions (DDIs) of drug candidates is important. Several CYP3A activators are known to lead to underestimation of DDIs. These compounds affect midazolam 1'-hydroxylation but not midazolam 4-hydroxylation. We used both metabolic reactions of midazolam to evaluate the activation and inhibition of CYP3A activators simultaneously. For our CYP inhibition assay using cocktail probe substrates, simultaneous liquid chromatography-tandem mass spectrometry monitoring of 1'-hydroxymidazolam and 4-hydroxymidazolam for CYP3A was established in addition to monitoring of 4-hydroxydiclofenac and 1'-hydroxybufuralol for CYP2C9 and CYP2D6. The results of our cocktail inhibition assay were well correlated with those of a single inhibition assay, as were the estimated inhibition parameters for typical CYP3A inhibitors. In our assay, a proprietary compound that activated midazolam 1'-hydroxylation and tended to inhibit 4-hydroxylation was evaluated along with known CYP3A activators. All compounds were well characterised by comparison of the results of midazolam 1'- and 4-hydroxylation. In conclusion, our CYP cocktail inhibition assay can detect CYP3A activation and assess the direct and time-dependent inhibition potentials for CYP3A, CYP2C9, and CYP2D6. This method is expected to be very efficient in the early stages of drug discovery. [ABSTRACT FROM AUTHOR]

Thermal treatment of coal byproducts has been shown to improve leaching characteristics of rare earth elements (REEs) in bituminous coal sources due to its influence on the associated minerals. This study investigated the impact of the calcination atmosphere on REE leaching behavior in different density fractions of Baker and Fire Clay seam coarse refuse sources using a thermogravimetric analyzer to create an oxidizing or reducing atmosphere at a desired temperature for 2 h. The effect on leaching characteristics was evaluated using 1.2 M sulfuric acid at 75°C for 5 h at 1% w/v solid concentration. Rare earth element (REE) recovery for the 2.2 specific gravity (SG) sink fraction improved by approximately 15 absolute percentage points at 1000°C relative to the 600°C calcined sample in an inert atmosphere and equilibrated within 10 min from the start of the test. Contrarily, thermal treatment at 1000°C under oxidizing atmosphere significantly reduced the REE recovery due to sintering of the clays, which limited access to the RE minerals for leaching. In general, thermal treatment of heavier fractions in both atmospheres significantly improved the light REE (LREE) recovery while the increase in heavy REE (HREE) recovery was relatively less. As common clay minerals in the coal sources, kaolinite and illite samples were tested under the same conditions and using a digital scanning calorimeter. The findings confirmed that the improvement observed in REE leaching through thermal treatment at 600°C was due to decarbonization for the lighter density fractions and dehydroxylation of clays. [ABSTRACT FROM AUTHOR]

Herein, we present a method for electrochemical‐induced 1,3‐oxohydroxylation of arylcyclopropanes with H2O as the green oxygen source. This transformation offers a regioselective route to highly functionalized β‐hydroxy ketones under oxidant‐ and metal‐free conditions. Notably, this electrochemical approach features simple operation, good regioselectivity, high functional group tolerance, and easy derivatization of the products. Mechanistic studies have provided solid evidences that 1,3‐diol acts as the crucial intermediate in this reaction, leading to the observed regioselectivity. [ABSTRACT FROM AUTHOR]

Owing to their high reactivity and selectivity, variations in the spin ground state and a range of possible pathways, high‐valent FeIV=O species are popular models with potential bioinspired applications. An interesting example of a structure–reactivity pattern is the detailed study with five nonheme amine‐pyridine pentadentate ligand FeIV=O species, including N4py: [(L1)FeIV=O]2+ (1), bntpen: [(L2)FeIV=O]2+ (2), py2tacn: [(L3)FeIV=O]2+ (3), and two isomeric bispidine derivatives: [(L4)FeIV=O]2+ (4) and [(L5)FeIV=O]2+ (5). In this set, the order of increasing reactivity in the hydroxylation of cyclohexane differs from that with cyclohexadiene as substrate. A comprehensive DFT, ab initio CASSCF/NEVPT2 and DLPNO‐CCSD(T) study is presented to untangle the observed patterns. These are well reproduced when both activation barriers for the C−H abstraction and the OH rebound are taken into account. An MO, NBO and deformation energy analysis reveals the importance of π(pyr) → π*xz(FeIII‐OH) electron donation for weakening the FeIII‐OH bond and thus reducing the rebound barrier. This requires that pyridine rings are oriented perpendicularly to the FeIII‐OH bond and this is a subtle but crucial point in ligand design for non‐heme iron alkane hydroxylation. [ABSTRACT FROM AUTHOR]

Here we show that the sp‐hybridized nitrogen cation is strongly stabilized by a peri‐iodine substituent in the tetralone system. The cation is captured by anionic species such as CF3CO2−, affording hypervalent iodine(III) compounds with a short nitrogen‐iodine (N−I) bond, in which the cation serves as a Lewis acid. Notably, the O−I bond of the O‐trifluoroacetate or O‐acetate is intrinsically weaker than the N−I bond due to its more ionic character and is further weakened by protonation in trifluoroacetic acid. As a result, the oxygen ligand can dissociate in the presence of a Brønsted acid, affording a I+ cation intermediate that retains the N−I bond. We isolated the cation as the tetrafluoroborate, and characterized it experimentally by 1H NMR spectroscopy and X‐ray structure analysis, and theoretically by means of DFT calculation. The results suggest that the N−I bonded cation is intrinsically stable, and is weakly coordinated with water and the BF4 counter anion or trifluoroacetate anion. This cation can be employed as a reagent for α‐oxidation of ketones. [ABSTRACT FROM AUTHOR]

It is a major challenge to perform one-pot hydroxylation of benzene to phenol under mild conditions, which replaces the environmentally harmful cumene method. Thus, finding highly efficient heterogeneous catalysts that can be recycled is extremely significant. Herein, a (POM)-based hybrid compound {[FeII(pyim)2(C2H5O)][FeII(pyim)2(H2O)][PMo V2 Mo VI9 V IV3 O42]}·H2O (pyim = 2-(2-pyridyl)benzimidazole) (Fe2-PMo11V3) was successfully prepared by hydrothermal synthesis using typical Keggin POMs, iron ions and pyim ligands. Single-crystal diffraction shows that the Fe-pyim unit in Fe2-PMo11V3 forms a stable double-supported skeleton by Fe–O bonding to the polyacid anion. Remarkably, due to the introduction of vanadium, Fe2-PMo11V3 forms a divanadium-capped conformation. Benzene oxidation experiments indicated that Fe2-PMo11V3 can catalyze the benzene hydroxylation reaction to phenol in a mixed solution of acetonitrile and acetic acid containing H2O2 at 60 °C, affording a phenol yield of about 16.2% and a selectivity of about 94%. [ABSTRACT FROM AUTHOR]