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• AKR1Cs display 5α-reductase activities towards oxymesterone, and the catalytic activities of AKR1C9 and AKR1C4 are higher than those of AKR1C1, AKR1C2 and AKR1C3. • 5α-reductase activities of AKR1Cs towards oxymesterone were higher than towards 17α-methyltestosterone, likely due to the presence of the C4‑hydroxyl group. • In contrast to 4-hydroxytestosterone, AKR1Cs has no 3α/β-HSD activity towards oxymesterone, likely due to the presence of the C17α-methyl group. • Oxymesterone was interconverted with 17α-methyltestosterone by both dehydroxylation and hydroxylation reactions catalyzed by AKR1Cs. The function of aldo-keto reductases (AKRs) is highly variable and is controlled by various groups within the steroid structure. The representative AKRs are AKR1C1-AKR1C4 from humans and AKR1C9 from rats (AKR1Cs). In this study, we focused on how the C4‑hydroxyl in the A-ring and C17α-methyl in the d-ring of oxymesterone (OXY) affect the catalytic function of AKR1Cs. We found that OXY bound to all AKR1Cs with greater affinity for AKR1C9 and AKR1C2, according to both autodocking predictions and binding experiments using microscale thermophoresis. Conversion and enzyme kinetic studies showed that AKR1C4 and AKR1C9 catalyzed approximately 90 % of OXY and that their Kcat and Kcat/Km values were higher than other AKR1Cs. Moreover, both purified AKR1C enzymes and AKR1C-transfected cells reduced OXY to 17α-methyl-4ξ,17β-dihydroxy-androstane-3-one with 5α-reductase activity, that was promoted by C4‑hydroxyl. Nevertheless, AKR1Cs lost the 3α/3β-hydroxysteroid dehydrogenase activity for OXY due to C17α-methyl and did not form 17α-methyl-3ξ, 4ξ, 17β-trihydroxy-androstane. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel triazine-based SOF was constructed based on the host-guest interaction. • The control of singlet oxygen and superoxide radical can be realized by using SOF as photosensitizers. • The singlet oxygen generated from SOF can be used for the photocatalytic oxidation of tricyclohexyl in water. • SOF can further be used for the promotion of the oxidative hydroxylation of arylboronic acids. The construction of supramolecular organic frameworks (SOFs) frequently leads to a substantial reduction in the efficiency of reactive oxygen species (ROS) generation. Hence, it is crucial to create and construct SOFs photocatalysts that have improved efficiency in generating ROS. In this research, we developed and produced a compound TN-3Ny, which is a derivative of 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine. This compound has the ability to create a supramolecular organic framework known as TN-SOF when it interacts with cucurbit[8]uril (CB[8]). The TN-3Ny monomer demonstrates the capacity to produce singlet oxygen (1O 2) and superoxide anion radical (O 2 •−). The incorporation of CB[8] leads to significant improvement in the effectiveness of generating 1O 2 and O 2 •− during the formation of TN-SOF, owing to the confinement effect exerted by the macrocyclic host molecule and framework structure. Furthermore, the utilization of 1O 2 and O 2 •− was implemented to augment the photocatalytic oxidation process of tricyclohexyl phosphine and phenylboronic acid. The TN-SOF demonstrated superior photocatalytic activity compared to the TN-3Ny monomer due to its extraordinary ability to generate 1O 2 and O 2 •−. As a result, it achieved impressive yields of 91% for tricyclohexyl phosphine and 90% for phenylboronic acid in an aqueous solution through photocatalytic oxidation. This presents a novel approach for the development of photosensitizers based on SOFs as well as their application in photocatalysis. [Display omitted] [ABSTRACT FROM AUTHOR]

• Affinity peptides successfully mediates the self-assembly of multiple enzymes. • Multi-enzyme complexes enable in situ elimination of H 2 O 2 from the cascade system. • Multi-enzyme assembly facilitates Fe(II)/α-KG-dependent dioxygenase catalysis. • (2 S ,3 R ,4 S)-4-hydroxyisoleucine was produced via one-pot cascade reaction. Fe(II)/α-ketoglutarate-dependent dioxygenases (Fe(II)/α-KG DOs) are powerful biocatalysts for C H bond hydroxylation, generating diverse high-value molecules. An inadequate cosubstrate α-KG supply leads to low yields of the desired products. Currently, L -glutamate oxidase (LGOX) is used to generate α-KG and cascades with catalase (KatG) to eliminate H 2 O 2 (a by-product of LGOX), an inhibitor of Fe(II)/α-KG DOs. However, free enzymes still cause H 2 O 2 accumulation, inhibiting Fe(II)/α-KG DO activity. Here, we employed RIAD-RIDD short peptides to form LGOX-KatG specific 1:2 ratio self-assembled tri-enzyme units using a scaffold-free strategy to obtain structural insights via computational analysis and to avoid H 2 O 2 toxicity to achieve high yield of a promising anti-diabetic drug (2 S ,3 R ,4 S)-4-hydroxyisoleucine in a one-pot system. A conversion of >95 % was achieved at a 100 mM isoleucine within 7 h, with 2.00 g·L−1·h−1 space-time yield. This work provides a universal, industrially attractive approach for supplying a cosubstrate for Fe(II)/α-KG DO catalyzing hydroxylation. [Display omitted] [ABSTRACT FROM AUTHOR]

• Chiral tertiary alcohols are synthesized by biocatalytic hydroxylation of C H bonds. • Good functional group tolerance and excellent enantioselectivities. • The reaction features mild reaction and employs molecular oxygen as an oxidant. • This approach avoids the use of pre-oxygen functionalized substrates. In view of the importance and beneficial characteristics of enantioenriched tertiary alcohols in pharmaceutical chemistry, efficient and green strategies for their synthesis are highly sought after. Here, we report a simple synthesis of the elusive chiral tertiary alcohols. A cytochrome P450 monooxygenase called P450 PL2 was developed to enable chiral tertiary alcohols by the benzylic C H bonds asymmetric hydroxylation of the racemic tertiary carbon substrates. This P450-catalyzed protocol provides various chiral tertiary alcohols with unexpectedly functional group tolerance and excellent enantioselectivities (up to >99 % ee). The method features mild reaction and employs molecular oxygen as an oxidant, avoids the use of pre-oxygen functionalized substrates. Preliminary molecular dynamics simulation studies were carried out to reveal the possible reasons for the exceptional selective hydroxylation of substrate during P450 PL2 catalysis. [Display omitted] [ABSTRACT FROM AUTHOR]

• An imidazolium ionic liquid catalysed strategy was suggested for aerobic α-hydroxylation of 2-methylcyclohexanone. • In IL media, anion was suggested to influence the reaction via local polarity. The ILs (BmimBF4 as model) could be separated by extraction with organic solvent directly. • Dissolved in DMSO, cation was proved to interact with carbonyl group and accelerate the reaction significantly with 1H NMR and ATR-FTIR. The great demands of chemical industries for environmental-friendly process draw interests on ionic liquids of high boiling points and low explosion risks. In this work, the aerobic α-hydroxylation of 2-methylcyclohexanone accelerated by 1-alkyl-3-methylimidazolium ionic liquids (ILs) was explored, where the ILs increased the efficiency considerably. ILs could also work as solvent and be separated from reaction mixture by extraction with organic solvents afterwards, where the anion moiety of ILs had a great impact on the reaction. After reaction, ethyl acetate was proved to be well-performed to separate BmimBF 4 for next use. Besides, the imidazolium cation moiety was proved to accelerate the reaction via 1H NMR and ATR-FTIR. For mechanistic study, an interaction between imidazolium cation and ketone was proposed and, moreover, supported by ESI-MS. This work should encourage the application and understanding of ionic liquids in aerobic oxidation. [Display omitted] [ABSTRACT FROM AUTHOR]

Selective hydroxylation of C(sp 3)–H bonds is a long-standing challenge in the organic synthesis field. We herein report an artificial P450 peroxygenase system facilitated by ω-pyridyl fatty acyl amino acids that can hydroxylate broad-spectrum alkanes, including linear and cyclic alkanes and benzylic and allylic alkane chains. Compared with the previously reported dual-functional small molecule (DFSM) with imidazole as a catalytic group (Im-DFSM), pyridyl DFSM (Pyd-DFSM) produced substantially higher total turnover numbers (TTNs) for the hydroxylation of medium-chain alkanes and cycloalkanes (C6–C8), e.g., 12.0-fold and 17.1-fold increased TTNs of P450 mutant F87A/T268V for heptane and cycloheptane, respectively. In addition, Pyd-DFSM altered the enantioselectivity of benzylic hydroxylation, e.g., it almost inverted the configuration observed in the benzylic hydroxylation of ethylbenzene and tetralin. More importantly, Pyd-DFSM showed excellent regioselectivity for allylic hydroxylation over epoxidation of terminal alkenes and cycloalkenes, e.g., up to 94% allylic hydroxylation of 1-hexene was observed. This work significantly enhances the catalytic toolbox of the DFSM-facilitated P450 peroxygenase system; it not only substantially expands the chemical space of P450 enzymes, but also provides an alternative solution for the selective hydroxylation of C(sp 3)–H bonds. [Display omitted] [ABSTRACT FROM AUTHOR]

• The bifunctional catalytic mechanisms of YN x C 4-x @Gra with hydroxylation effect were discussed for the first time. • Hydroxylation is beneficial for improving the catalytic activity of stable coordination configurations. • YN 2 C 2oppo /N 2 C 2pen /N 3 C 1 OH@Gra with the stable coordination environment exhibit excellent bifunctional activity. • The descriptor d-electron number was introduced to rapidly predict catalytic activity. The oxygen electrode reactions (ORR/OER) are the key to electrochemical storage and conversion technologies. In this study, the bifunctional electrocatalytic mechanisms of YN x C 4-x @Gra with hydroxylation effect were discussed extensively. Firstly, the configurations with N coordination have good stability. Secondly, YN 1 C 3 /N 2 C 2hex @Gra with unstable coordination environment break the scale relationships between adsorption intermediates and exhibit outstanding OER performance with ηOER of 0.45 V and 0.46 V. Thirdly, YN 2 C 2oppo /N 2 C 2pen /N 3 C 1 OH@Gra with stable coordination environment demonstrate excellent bifunctional activity with ηORR of 0.48 V, 0.54 V, and 0.53 V and ηOER of 0.71 V, 0.73 V, 0.63 V. Forth, for catalysts with stable coordination environments, there are scale relationships between the adsorption of intermediates, and thus volcanic curves were constructed. Finally, the d-electron number was introduced to predict catalytic performance, saving time and computative costs for screening potential catalyst configurations. All in all, YN x C 4-x @Gra catalysts are potential oxygen electrode bifunctional electrocatalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

• A new biocatalytic approach to convert Grundmann's Ketone and its derivatives. • Up to 99% conversion and regioselectivity enabled by peroxygenase. • Expanding the use of enzymes in the transformation of vitamin D related compounds. • Independence of NAD(P)H cofactors, easy scalability to 0.2 L reaction scale. Peroxygenases are selective catalysts for C-H bond oxyfunctionalization reactions, however, their potential for organic synthesis still needs to be explored. 25-Hydroxy-Grundmann's ketone is a key structural motifs in various biologically active vitamin D 3 analogues. In this study, we report the use of unspecific peroxygenase from Agrocybe aegerita as a highly selective catalyst for the C25 hydroxylation of Grundmanns's ketone and its analogues. Under the optimised conditions, excellent conversion (> 99%) and regioselectivity (> 99%) was obtained. The selected hydroxylation processes were performed on an increased lab scale (up to 200 mL) with up to 1 mmol substrate, which led in 85.7% isolated yield.This simple biocatalytic method holds great potential in streamlining the synthetic pathways of vitamin D 3 analogues. [Display omitted] [ABSTRACT FROM AUTHOR]

• In situ and controllable generation of H 2 O 2 via the All-in-One (AiO) electrode. • New application of the AiO electrode in the electroenzymatic process. • AiO electrode-aided enzymatic hydroxylation catalyzed by the recombinant unspecific peroxygenase. • Total turnover number up to 450,000 mol−1 was obtained in a bioelectrochemical system. The versatile unspecific peroxygenase from the fungus Agrocybe aegerita (Aae UPO) is capable to perform hydroxylation of various substrates, even unactivated C H bonds. The technical application of Aae UPO is still limited due to an instability towards its co-substrate hydrogen peroxide (H 2 O 2). Electrochemical synthesis of H 2 O 2 is an attractive approach that provides controllable in situ generation of H 2 O 2. The aims of this study are to promote catalyst efficiency and develop an individually tailored system for H 2 O 2 -dependent reactions. Herein, an All-in-One electrode (AiO) system with a carbon felt cathode is used to generate H 2 O 2 in situ and combined for the first time with an enzymatic hydroxylation. The AiO electrode combines the counter and working electrode in a single rod structure. This shape provides convenient integration into conventional bioreactors, thus, converting them into bioelectrochemical systems (BES). Hydroxylation of 4-ethylbenzoic acid (EBA) catalyzed by the recombinant Aae UPO (r Aae UPO) was chosen as the model reaction. Total turnover number (TTN) up to 450,000 mol mol−1 and turnover frequency (TOF) up to 7.7 s −1 were achieved using the AiO electrode system. The H 2 O 2 productivity was identified as the limiting factor in the hydroxylation of EBA. However, with numbering-up or surface enlargement, this process could have great potential as an optimizable platform for H 2 O 2 -dependent enzymatic reactions. [Display omitted] [ABSTRACT FROM AUTHOR]

• The surface hydroxylation of CrO x /Al 2 O 3 catalysts can construct oxygen defect sites. • The thermally unstable oxygen defect sites were responsible for catalyzing PDH. • The strategy of constructing oxygen defect sites is applicable to other oxide materials. Propane dehydrogenation (PDH) has emerged as an efficient complementary process for producing propylene. The fundamental understanding of reaction mechanism of traditional CrO x -based catalysts is important for designing novel PDH catalysts. Here, the evolution of surface Cr species was investigated by means of steam pre-treatment to introduce a certain amount of hydroxyl groups on deeply reductive Cr 2 O 3 /Al 2 O 3 catalysts without influencing the valence states and aggregated states. The surface structural features of CrO x /Al 2 O 3 catalysts were investigated by FT-IR, TGA, XPS, NH 3 -TPD, and Py-IR characterization techniques. It demonstrated that more hydroxyls were produced on the surface of catalysts under steam treatment. Subsequently, hydroxyl groups were mostly removed during the H 2 thermal treatment and abundant oxygen defect sites were generated. These defect sites showed an increasing number of acidic sites, thus exhibiting a relatively high PDH activity. This strategy of introducing hydroxyl groups to construct oxygen defect sites is also applicable to other oxide materials, which offers a novel perspective for rational catalyst design. [Display omitted] Hydroxyl group as active intermediate is helpful to construct thermally unstable oxygen defective sites of CrO x /Al 2 O 3 catalysts for catalyzing propane dehydrogenation. [ABSTRACT FROM AUTHOR]

• Remarkable characteristics of mesoporous Fe 2 O 3 -TiO 2 mixed oxides were studied. • Fe-loading influenced the acidic property of the catalyst. • The acidic property of the catalyst plays a predominant role in the selective hydroxylation of benzene. The omnipresence of C H bonds in organic molecules enamors chemists for the functionalization of C H bonds towards value-added molecular scaffolds. Mesoporous Fe 2 O 3 -TiO 2 mix-oxide catalyst has been successfully synthesized via a triblock-copolymer (P123) mediated sol-gel method and catalytically tested in selective hydroxylation of benzene. The as-synthesized catalysts were comprehensively characterized by powder XRD, Raman spectroscopy, FT-IR, N 2 -physisorption, FESEM, HRTEM, XPS, and NH 3 -TPD techniques. The physicochemical characterizations evidence that Fe(III) ions incorporate into the pure anatase TiO 2 lattice framework and the crystallite size decreases as iron concentration increases. The XPS analyses confirm the Fe3+ state (BE 710.3 eV) in Fe-O-Ti with a peak at 712.1 eV for Fe3+ of Fe 2 O 3. The NH 3 -TPD results show that the 5 wt% Fe-TiO 2 has a higher total acidity of 105 µmol/g. Interestingly, a further increase in iron amount decreases the total acidity. Herein, we observe that the surface acidity directs the selectivity towards phenol. The effect of different reaction parameters was carefully investigated. Under the optimized conditions, 5% Fe-TiO 2 with notified strong acid sites gives a higher phenol yield of 31.2% with > 99% selectivity; moreover, the catalyst is reusable at least four times. C H activation of benzene over mesoporous Fe 2 O 3 -TiO 2 mixed oxide synthesized by conventional sol-gel method [Display omitted] [ABSTRACT FROM AUTHOR]

• The texture properties of hierarchical TS-1 zeolites can be precisely modulated by the TritonX homologues with different amounts of ethoxide. • The mesoporosity and Ti content of hierarchical Ti-rich determine the conversion of benzene. • Introducing additional mesoporosity into the hierarchical TS-1 facilitates the direct the oxidation of benzene. The hydrothermal approach was used to effectively synthesis hierarchical TS-1 utilizing the green and inexpensive surfactant TritonX homologues with varying amounts of ethylene oxide groups. The textural property of obtained materials can be modulated by varying the number of ethylene oxide groups of the TritonX homologues. The mesoporous size of hierarchical TS-1 depends on the micelles size of TritonX homologues. The synthesized samples have significant intracrystalline mesopores with a pore size range of 3.5–4.5 nm. The impact of various ethylene oxide group counts of TritonX homologous on the structure, texture properties, and titanium species was investigated using a variety of characterization methods. The hydroxylation of benzene with the H 2 O 2 as oxidizer was used to investigate the catalytic properties of hierarchical TS-1. The catalytic properties and stability of the resulting materials were noticeably improved in the hydroxylation of benzene in comparison with the traditional TS-1. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel peroxygenase from Galerina marginata (GmaUPO) was identified by database mining • GmaUPO was recombinatly expressed in Pichia pastoris initially characertized • GmaUPO catalyzes the H2O2-driven oxyfunctionalisation of alkanes, alkenes, alcohols and thioethers • Molecular modelling puts the basis for a molecular understanding of factors influencing GmaUPO's activity and selectivity Unspecific peroxygenases (UPOs, EC 1.11.2.1) are promising oxyfunctionalization catalysts because of their unique stereoselectivity. However, so far only a few UPOs have been reported. In this study, gene mining was used to identify a gene from Galerina marginata that coded for a novel UPO (Gma UPO). Gma UPO was expressed in Pichia pastoris X-33 by scale-up fermentation (the UPO activity of the culture supernatant was 118 U/L). Gma UPO exhibited a molecular weight of 40 kDa and exhibited highest activity at 35°C and pH 9, respectively. Furthermore, Gma UPO was demonstrated to catalyze the epoxidation, sulfoxidation, and hydroxylation of common substrates, particularly fatty acids such as tridecanoic acid. The molecular basis for Gma UPO regioselectivity for fatty acid hydroxylation was explored by molecular modelling. The regioselectivity was mostly governed by the architecture of the enzyme's active site. [Display omitted] [ABSTRACT FROM AUTHOR]

• A hydrothermal carbon with oxygen groups and polyfuran units was constructed. • The catalyst was efficient in metal-additive-free oxygen-mediated benzene to phenol. • Surface oxygen groups as the active sites to form ·OH radials to oxidize benzene. • The polyfuran units promoted the O 2 adsorption and activation to accelerate reaction. Direct benzene hydroxylation with dioxygen (O 2) is among the most promising alternative pathways for green phenol production, but efficient catalysis systems usually involve metal species or other additives such as sacrificial agents. In this work, we designed a carbon catalyst from the hydrothermal treatment of biomass-derived sucrose and constructed a metal-/additive free heterogeneous catalytic system for benzene hydroxylation to phenol with O 2. The champion carbon sample gave a high phenol yield of 13.4%. The catalyst was facilely recovered and reused without apparent deactivation. There abundant oxygen functional groups such as phenolic and quinone carbonyl groups served as the active sites and polyfuran units accelerated the O 2 adsorption and activation. The synergistic effect of these surficial organic groups is conducive to the formation of reactive oxygen species, hydroxyl radicals, which effectively oxidized the benzene to phenol. Sucrose-derived hydrothermal carbon material with abundant polyfuran units allowed the efficient metal- and additive-free benzene hydroxylation to phenol with O 2. [Display omitted] [ABSTRACT FROM AUTHOR]

• Direct hydroxylation of arenes to phenols was reported. • A copper(II) complex of an N4 aminobenzimidazole was used as an efficient catalyst. • Hydrogen peroxide was used as a green oxidant. Direct hydroxylation of arenes to phenols with hydrogen peroxide as a green oxidant is an attractive approach. In the present study, we prepared several copper (II) complexes bearing tetra- (N4), tri- (N3) and pentadentate (N5) ligands, and the copperII-N4 complex could act as an efficient catalyst for hydroxylation of benzenes with H 2 O 2 (up to 22.4% yield of phenols with 10.0 equiv. H 2 O 2 , and 38.0% yield of phenol with limited amount of H 2 O 2) at room temperature. X-ray crystallographic analysis indicates that the CuII-N4 complex exhibits a square-pyramidal geometry and that two methyl groups connecting to the diamine are cis to each other. In comparison, copper(II) complexes supported by tri- (N3) and pentadentate (N5) ligands were also evaluated in the hydroxylation of benzene, demonstrating inferior performance. [Display omitted]. [ABSTRACT FROM AUTHOR]

• Use cheap copper catalysts instead of precious metals. • Copper phthalocyanines working as molecule catalysts can efficiently activate the reaction at mild reaction conditions without any other ligands. Aryl iodine, aryl bromine and aryl chlorine can be activated with the yield up to 98%. • The molecule catalysts have the heterogenerous property and can be recycled without losing activity for 6 times. • This is the first work that has realized the hydroxylation of aryl halides by metal phthalocyanines as catalysts. We have researched and developed a series of copper phthalocyanine derivatives as new highly active and reusable catalysts for the hydroxylation of (hetero)aryl halides. The perfluorinated copper phthalocyanine (CuPcF 16) showed the highest activity for the hydroxylation of aryl iodide with an excellent yield (up to 98%) under low catalytic loading (0.5 mol% CuPcF 16). Similarly, the hydroxylation of aryl bromides and aryl chlorides catalyzed by CuPcF 16 also had high activity with 42∼98% yield. Moreover, the recyclability of this catalyst can up to 6 times without significant loss in catalytic activity. [Display omitted] [ABSTRACT FROM AUTHOR]

• Correlation of solvent descriptors with the hydroformylation activity established. • The net electron-giving ability of solvent is essential to the selectivity of glycolaldehyde. • Polar aprotic solvents influence the dissociation of Rh-H to form the anionic Rh species. • Generating MeOH is relatively easier in non-polar solvents. • HCHO activation requires a cooperation of anionic Rh species and protonated solvent molecule. The homogeneous catalytic hydroformylation of formaldehyde to glycolaldehyde is a key intermediate step for one-step synthesis of ethylene glycol from syngas. The effect of solvent nature on the catalytic response and mechanistic pathway has been rarely studied. A group of parameters (e.g., ε r , μ, α, β) describing the solvent electronic features were achieved for a descriptor database and correlated with the hydroformylation activity. The net electron donating ability has been found to govern the selectivity to glycolaldehyde. The DFT calculation demonstrates the stronger electron-donating solvents serve to lower the energy required for the dissociation of Rh-H to form the anionic rhodium species, which induces the anion mechanism that preferentially facilitates the glycolaldehyde generation. The polar aprotic solvents can be protonated in the dissociation of Rh-H to the anionic species and participate in the HCHO activation through the proton transfer from solvent molecules to HCHO, resulting in the formation of hydroxymethyl species. Graphic abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

• Two novel diiron core complexes (μ-budt)Fe 2 (CO) 5 (DPEphos) (1) and (μ-budt)Fe 2 (CO) 5 (Xantphos) (2) supported by rigid heterocyclic xanthene-like diphosphine ligands were designed and synthesized. • Complex 1 exhibits outstanding catalytic performance, attaining 57.7% phenol conversion and 49.6% DHB yield, both of which are at the forefront of catalytic phenol hydroxylation. • The DFT calculations were performed to optimize the geometrical structures and obtain the frontier molecular orbitals. • The mechanism of phenol hydroxylation using 1 as a catalyst was proposed. • Hydroxyl radicals (•OH) were generated in the catalytic reaction, as demonstrated by electron spin resonance (ESR). Hydroquinone (HQ) and catechol (CAT) are the important raw materials in the chemical industry, which can be produced through a direct catalytic hydroxylation process using hydrogen peroxide as an oxidant. Herein, we report two novel diiron core complexes (μ-budt)Fe 2 (CO) 5 (DPEphos) (1) and (μ-budt)Fe 2 (CO) 5 (Xantphos) (2) supported by rigid heterocyclic xanthene-like diphosphine ligands which exhibit high selectivity and activity in phenol hydroxylation. The structures of complexes 1 and 2 were characterized by FT-IR, UV–vis, 1H NMR, 31P-NMR, X-ray crystallography, while the catalytic products were tested by using HPLC. The FT-IR and UV–vis spectra reveal that two diphosphine ligands exhibit similar impacts on the structure of parent complex (μ-budt)Fe 2 (CO) 6 [budt = SCH(CH 3)CH 2 CH 2)S]. Despite the similarity of ligands' impact on the structure of the parent complex, the catalytic behavior was strongly influenced by the electronic and steric effects. The factors influencing the catalytic activity were optimized, including catalyst dosage, phenol/ H 2 O 2 molar ratio, reaction temperature, and time. Under the optimal conditions, 1 exhibits great catalytic performance with 57.7% phenol conversion and 49.6% DHB yield, both of which are remarkable. The mechanism of phenol hydroxylation using 1 as a catalyst was also proposed. Hydroxyl radicals (•OH) were generated in the catalytic reaction, as demonstrated by electron spin resonance (ESR). [Display omitted]. [ABSTRACT FROM AUTHOR]

• Tyrosinase can hydroxylate a broad range of monophenols. • In Type A substrates, the o- quinone evolution generates o- diphenol in the medium. • In Types B, C and D substrates, the evolution does not accumulate o- diphenol. • Hydrogen peroxide transforms Em to Eox and the enzyme has hydroxylating activity. • In presence of monophenols, Michaelis constant for oxygen is very low. The mechanism of action of tyrosinase on monophenols is complex, several processes overlap in time, such as the hydroxylation of monophenols to o- diphenols, the oxidation of these to o- quinones and the evolution of the latter towards melanin. The enzyme's mechanism of action is unique but depending on the chemical nature of the substrate it may show different exceptions. In this review we want to dissect the kinetic mechanism for the action of the enzyme on: a) L-tyrosine, the physiological substrate for mammalian tyrosinase, and related compounds, whose o- quinones in their chemical evolution accumulate o- diphenol in the medium (Type A). b) Substrates that cannot accumulate o- diphenol in the medium because it is easily oxidized and they need the presence of hydrogen peroxide for the enzyme to show activity, such as hydroquinone and related compounds (Type B). c) Substrates that release o- diphenol into the medium and the enzyme oxidizes it generating a stable o- quinone and therefore does not generate more o- diphenol in the medium, as is the case of 4‑tert-butylphenol and related compounds (Type C). d) Substrates that do not release or generate o- diphenol in the medium, as is the case with deoxyarbutin, which produces a stable o- quinone (Type D). The different mechanisms that explain the enzymatic activity are proposed, a kinetic analysis is established for each mechanism and by means of numerical integration results are obtained that are discussed and compared with experimental data. To help and support the results and discussion, molecular docking for substrates (L-tyrosine, hydroquinone, 4‑tert-butylphenol, and deoxyarbutin) to both the oxy and met forms of tyrosinase was carried out. [Display omitted] [ABSTRACT FROM AUTHOR]

• Photocatalytic hydroxylation of benzene to phenol can be achieved by using O 2 as an oxidant. • The sodium decatungstate (W 10 O 32 4−) is an effective photocatalyst for the benzene hydroxylation reaction in an aqueous solution. • High phenol yield (17–41%) and selectivity (76–82%) can be obtained within 60 min under ambient conditions. • The addition of acetic acid as a co-solvent can significantly enhance phenol formation. A one-pot hydroxylation reaction, in which benzene is converted to phenol using oxygen under mild conditions has attracted attention as an environmentally benign alternative to the cumene method. Herein, we report on the photocatalytic hydroxylation of benzene to phenol with O 2 by using sodium decatungstate (W 10 O 32 4−) in air atmosphere (1 atm) and at low temperature (10 °C). W 10 O 32 4− was active for the benzene hydroxylation process in pure water, which achieved a ca. 16–23% phenol yield with a ca. 61–70% selectivity within 60 min. The phenol yield and the selectivity were improved through the addition of acetic acid to the reaction solution. This enhancement was due to the improved benzene solubility and suppressed benzene vaporization and phenol overoxidation. The effect of the reaction conditions on the phenol formation was investigated in detail. Under anaerobic conditions, the reduced form of W 10 O 32 4− was generated, with the simultaneous formation of phenol, whereas phenol was not formed in the reoxidation of the reduced decatungstate with O 2. According to a kinetic isotopic effect, the C−H bond activation process in benzene hydroxylation was dominated by electron transfer (KIE, k H / k D = 1.0). The reaction mechanism for hydroxylation of benzene to phenol was also discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct conversion of benzene to Phenol using heterogeneous catalysts. • Benzene hydroxylation over transition metal-based mesoporous catalysts. • The effect of reaction conditions, the support's nature on the phenol efficiency. • A comparison of synthesis methods of heterogeneous catalysts. This review provides an outlook on heterogeneous catalysts for direct hydroxylation of benzene to phenol (DHBP) with a special focus on various mesoporous transition metal-based catalysts. Among all molecular sieves, mesoporous materials with high surface area and pore volume, tuneable pore sizes, and rich morphology can serve as both efficient catalytic supports and catalysts. The modification of meso‑pores with transition metal species provides the materials with great properties, making the catalysis process highly selective and controllable. This emerging area can provide researchers with great opportunity to introduce novel heterogeneous catalysts from both industrial and environmentally friendly viewpoints. [ABSTRACT FROM AUTHOR]

• TS-1 nanozeolite was achieved in a concentrated gel system through a two-step synthesis method. • The effect of the addition of L-lysine on the structure of zeolite was proposed. • The formation mechanism of nanozeolite was speculated. • TS-1 nanozeolite showed the excellent catalytic performance in hydroxylation of benzene. L-lysine is used as a crystallization regulator, and a two-step synthesis method is adopted in a concentrated gel system, which provides a new route to synthesize of nano-sized TS-1 zeolite. The new synthesis strategy was used to successfully synthesize TS-1 zeolite with a particle size less than 100 nm. The rate of crystal nucleation is faster than the crystal growth at the low temperature in the first step. Introduction of L-lysine can prevent crystal growth to form nano-sized TS-1 zeolite at the high temperature in the second step. Meanwhile, L-lysine decrease the pH value of the gel system, which is favorable for Ti atoms to incorporate the TS-1 framework. TS-1 nanozeolite can effectively reduce the diffusion resistance, and nanozeolite has a large specific surface area and high stability. Therefore, TS-1 nanozeolite exhibits the excellent catalytic performance during the hydroxylation of benzene. The conversion of benzene has been greatly improved and the types of by-products are effectively reduced. The conversion of benzene reached 50.2%, and the yield of phenol was 30.8% without by-product benzoquinone. TS-1 nano-zeolite as a catalyst for benzene hydroxylation shows great potential in industrial application. [Display omitted] [ABSTRACT FROM AUTHOR]

• Bis(oxazoline) complexes of nickel catalyze alkane hydroxylation with m-CPBA. • Structure of bis(oxazoline) ligands influences the catalytic performance. • Durability of catalysts toward O 2 depends on the structure of the bis(oxazoline) ligands. Applicability of the oxazoline-based compounds, bis(2-oxazolynyl)methane (BOX) and 2,6-bis(2-oxazolynyl)pyridine (PyBOX), as supporting ligands of nickel(II) complexes for the catalysis of aliphatic C H hydroxylation with m -CPBA (meta -chloroperoxybenzoic acid) was explored. Substituent groups at the fourth and fifth positions of oxazoline rings and the bridgehead carbon atom of the BOX derivatives affected the catalytic performances toward cyclohexane hydroxylation. Presence of dioxygen led to a reduced catalytic performance of the nickel complexes, except in the case of a fully substituted BOX ligand complex. [Display omitted] [ABSTRACT FROM AUTHOR]