108-39-4Relevant articles and documents
Ene Reductase Enzymes for the Aromatisation of Tetralones and Cyclohexenones to Naphthols and Phenols
Kelly, Paul P.,Lipscomb, David,Quinn, Derek J.,Lemon, Ken,Caswell, Jill,Spratt, Jenny,Kosjek, Birgit,Truppo, Matthew,Moody, Thomas S.
, p. 731 - 736 (2016)
Ene reductases (EREDs) have great potential as oxidation biocatalysts, as demonstrated by their efficient conversion of a number of tetralones to the corresponding naphthols. Of 96 enzymes tested, 57 were able to produce 2-naphthol in this way. Further tests with substituted tetralones revealed typically high conversions up to >99%. The reactions were performed under mild conditions in aqueous buffer with only co-solvent, biocatalyst and oxidation substrate required for conversion. Production of a methoxy-substituted naphthol was also successfully performed on a gram scale, with 91% yield. This methodology provides a new avenue to produce substituted naphthols as valuable building blocks, with the possibility to extend the approach to the production of phenols also being demonstrated.
Postsynthetic metalation of bipyridyl-containing metal-organic frameworks for highly efficient catalytic organic transformations
Manna, Kuntal,Zhang, Teng,Lin, Wenbin
, p. 6566 - 6569 (2014)
We have designed highly stable and recyclable single-site solid catalysts via postsynthetic metalation of the 2,2-bipyridyl-derived metal-organic framework (MOF) of the UiO structure (bpy-UiO). The Ir-functionalized MOF (bpy-UiO-Ir) is a highly active catalyst for both borylation of aromatic C-H bonds using B2(pin)2 (pin = pinacolate) and ortho-silylation of benzylicsilyl ethers; the ortho-silylation activity of the bpy-UiO-Ir is at least 3 orders of magnitude higher than that of the homogeneous control. The Pd-functionalized MOF (bpy-UiO-Pd) catalyzes the dehydrogenation of substituted cyclohexenones to afford phenol derivatives with oxygen as the oxidant. Most impressively, the bpy-UiO-Ir was recycled and reused 20 times for the borylation reaction without loss of catalytic activity or MOF crystallinity. This work highlights the opportunity in designing highly stable and active catalysts based on MOFs containing nitrogen donor ligands for important organic transformations.
Continuous-flow generation of anhydrous diazonium species: Monolithic microfluidic reactors for the chemistry of unstable intermediates
Fortt, Robin,Wootton, Robert C. R.,De Mello, Andrew J.
, p. 762 - 768 (2003)
Monolithic microfluidic reactors for the safe, expedient, and continuous synthesis of products involving unstable intermediates were fabricated and assessed. The formation of diazonium salts in anhydrous conditions and their subsequent in situ chlorination within microfiuidic channels under hydrodynamic pumping regimes is presented. Significant enhancements in yield were observed due to enhanced heat and mass transfer in microfluidic systems. Analysis performed using off-line GC and GC-MS was compared with on-line, on-chip Raman spectroscopy for the direct determination of analytes.
One-pot synthesis of benzofurans via heteroannulation of benzoquinones
Pirouz, Maryam,Saeed Abaee,Harris, Pernille,Mojtahedi, Mohammad M.
, p. 24 - 31 (2021)
Three different reactions were explored leading to the synthesis of various benzofurans. All reactions took place under AcOH catalysis in a one-pot manner. As a result, benzoquinone derivatives underwent heteroannulation with either itself or cyclohexanones to produce furanylidene-benzofuran or benzofuran structures, respectively.
Photochemical Transformationos of Protonated Phenols. A One-Step Synthesis of Umbellulone from Thymol
Baeckstroem, Peter,Jacobsson, Ulla,Koutek, Bohumir,Norin, Torbjoern
, p. 3728 - 3732 (1985)
UV irradiation of thymol (7) at 254 or 300 nm in trifluoromethanesulfonic acid affords ten products, eight of which have been isolated and characterized.Four competitive processes are suggested to be operating in the formation of the photoproducts: (i) regioselective type A rearrangement leading to umbellulone (8, about 10percent, (ii) formal C2->C3 migration by type A rearrangement and ring opening which affords the principal products, 3-isopropyl-5-methylphenol (12, 17percent), (iii) intermolecular transalkylation leading to diisopropylphenols 13-15 (17percent), and (iv) formation ofpiperitenone (10, 5percent) initiated by hydrogen abstraction.A mechanism for the formation of 10 is proposed.Both para- and ortho-protonated 7 are suggested to be involved in product formation.
Palladium-Catalyzed Hydrodehalogenation of Haloaromatic Compounds
Pandey, Paras N.,Purkayastha, Makhan L.
, p. 876 - 878 (1982)
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Aerobic dehydrogenation of cyclohexanone to phenol catalyzed by Pd(TFA)2/2-dimethylaminopyridine: Evidence for the role of Pd nanoparticles
Pun, Doris,Diao, Tianning,Stahl, Shannon S.
, p. 8213 - 8221 (2013)
We have carried out a mechanistic investigation of aerobic dehydrogenation of cyclohexanones and cyclohexenones to phenols with a Pd(TFA) 2/2-dimethylaminopyridine catalyst system. Numerous experimental methods, including kinetic studies, filtration tests, Hg poisoning experiments, transmission electron microscopy, and dynamic light scattering, provide compelling evidence that the initial PdII catalyst mediates the first dehydrogenation of cyclohexanone to cyclohexenone, after which it evolves into soluble Pd nanoparticles that retain catalytic activity. This nanoparticle formation and stabilization is facilitated by each of the components in the catalytic reaction, including the ligand, TsOH, DMSO, substrate, and cyclohexenone intermediate.
The multifunctional globin dehaloperoxidase strikes again: Simultaneous peroxidase and peroxygenase mechanisms in the oxidation of EPA pollutants
Ghiladi, Reza A.,Malewschik, Talita,McGuire, Ashlyn H.,de Serrano, Vesna
, (2019)
The multifunctional catalytic hemoglobin dehaloperoxidase (DHP) from the terebellid polychaete Amphitrite ornata was found to catalyze the H2O2-dependent oxidation of EPA Priority Pollutants (4-Me-o-cresol, 4-Cl-m-cresol and pentachlorophenol) and EPA Toxic Substances Control Act compounds (o-, m-, p-cresol and 4-Cl-o-cresol). Biochemical assays (HPLC/LC-MS) indicated formation of multiple oxidation products, including the corresponding catechol, 2-methylbenzoquinone (2-MeBq), and oligomers with varying degrees of oxidation and/or dehalogenation. Using 4-Br-o-cresol as a representative substrate, labeling studies with 18O confirmed that the O-atom incorporated into the catechol was derived exclusively from H2O2, whereas the O-atom incorporated into 2-MeBq was from H2O, consistent with this single substrate being oxidized by both peroxygenase and peroxidase mechanisms, respectively. Stopped-flow UV–visible spectroscopic studies strongly implicate a role for Compound I in the peroxygenase mechanism leading to catechol formation, and for Compounds I and ES in the peroxidase mechanism that yields the 2-MeBq product. The X-ray crystal structures of DHP bound with 4-F-o-cresol (1.42 ?; PDB 6ONG), 4-Cl-o-cresol (1.50 ?; PDB 6ONK), 4-Br-o-cresol (1.70 ?; PDB 6ONX), 4-NO2-o-cresol (1.80 ?; PDB 6ONZ), o-cresol (1.60 ?; PDB 6OO1), p-cresol (2.10 ?; PDB 6OO6), 4-Me-o-cresol (1.35 ?; PDB 6ONR) and pentachlorophenol (1.80 ?; PDB 6OO8) revealed substrate binding sites in the distal pocket in close proximity to the heme cofactor, consistent with both oxidation mechanisms. The findings establish cresols as a new class of substrate for DHP, demonstrate that multiple oxidation mechanisms may exist for a given substrate, and provide further evidence that different substituents can serve as functional switches between the different activities performed by dehaloperoxidase. More broadly, the results demonstrate the complexities of marine pollution where both microbial and non-microbial systems may play significant roles in the biotransformations of EPA-classified pollutants, and further reinforces that heterocyclic compounds of anthropogenic origin should be considered as environmental stressors of infaunal organisms.
Gold-Catalyzed Proto- and Deuterodeboronation
Barker, Graeme,Webster, Stacey,Johnson, David G.,Curley, Rachel,Andrews, Matthew,Young, Paul C.,MacGregor, Stuart A.,Lee, Ai-Lan
, p. 9807 - 9816 (2015)
A mild gold-catalyzed protodeboronation reaction, which does not require acid or base additives and can be carried out in "green" solvents, is described. As a result, the reaction is very functional-group-tolerant, even to acid- and base-sensitive functional groups, and should allow for the boronic acid group to be used as an effective traceless directing or blocking group. The reaction has also been extended to deuterodeboronations for regiospecific ipso-deuterations of aryls and heteroaryls from the corresponding organoboronic acid. Based on density functional theory calculations, a mechanism is proposed that involves nucleophilic attack of water at boron followed by rate-limiting B-C bond cleavage and facile protonolysis of a Au-σ-phenyl intermediate.
Cesium carbonate mediated aryl triflate esters' deprotection
Green, Alice E.,Agouridas, Vangelis,Deniau, Eric
, p. 7078 - 7079 (2013)
A variety of diversely substituted aryl triflate esters were efficiently deprotected to the parent phenols by exposure to cesium carbonate in toluene. This procedure proved highly compatible with existing functional groups.
Pd0-PyPPh2@porous organic polymer: Efficient heterogeneous nanoparticle catalyst for dehydrogenation of 3-methyl-2-cyclohexen-1-one without extra oxidants and hydrogen acceptors
Chen, Xingkun,Wang, Wenlong,Zhu, Hejun,Yang, Wenshao,Ding, Yunjie
, p. 49 - 56 (2018)
In this contribution, we have developed an efficient and recyclable porous organic polymer (POP) supported Pd nanoparticle catalyst (Pd°-PyPPh2@POP) for dehydrogenation of 3-methyl-2-cyclohexen-1-one. This heterogeneous catalytic system represents a totally clean process without using any extra oxidant and hydrogen acceptors. The SEM-EDS mapping images of the Pd°-PyPPh2@POP catalyst reveal the highly uniformly dispersed character of C, Pd, P and N elements. The coordination bonds between Pd nanoparticle and exposed P atom as well as N atom on the surface of PyPPh2@POP polymer are confirmed by means of solid-state 31P NMR and XPS. Importantly, both P atom and pyridyl ring on the PyPPh2@POP polymer are themselves used as solid base over the Pd°-PyPPh2@POP catalyst, leading to a catalytic conversion of 88.2% even without the employment of inorganic base additives (K2CO3). Our results have provided a strategy for designing highly active bifunctional POP supported nanoparticle catalysts.
Imidazolium-urea low transition temperature mixtures for the UHP-promoted oxidation of boron compounds
Martos, Mario,Pastor, Isidro M.
, (2022/01/03)
Different carboxy-functionalized imidazolium salts have been considered as components of low transition temperature mixtures (LTTMs) in combination with urea. Among them, a novel LTTM based on 1-(methoxycarbonyl)methyl-3-methylimidazolium chloride and urea has been prepared and characterized by differential scanning calorimetry throughout its entire composition range. This LTTM has been employed for the oxidation of boron reagents using urea-hydrogen peroxide adduct (UHP) as the oxidizer, thus avoiding the use of aqueous H2O2, which is dangerous to handle. This metal-free protocol affords the corresponding alcohols in good to quantitative yields in up to 5 mmol scale without the need of further purification. The broad composition range of the LTTM allows for the reaction to be carried out up to three consecutive times with a single imidazolium salt loading offering remarkable sustainability with an E-factor of 7.9, which can be reduced to 3.2 by the threefold reuse of the system.
Highly selective demethylation of anisole to phenol over H4Nb2O7modified MoS2catalyst
Ji, Na,Wang, Zhenjiao,Diao, Xinyong,Jia, Zhichao,Li, Tingting,Zhao, Yujun,Liu, Qingling,Lu, Xuebin,Ma, Degang,Song, Chunfeng
, p. 800 - 809 (2021/02/26)
Hydrogenolysis of lignin to obtain value-added phenolic chemicals is an important approach for its comprehensive utilization. Herein, H4Nb2O7modified MoS2catalyst with short slabs and narrow stacking degree was successfully synthesized by the one step hydrothermal method and used in the selective demethylation of anisole to phenol. The MoS2-H4Nb2O7-160 catalyst exhibited the best activity with 97.7% conversion of anisole and 98.0% selectivity of phenol under 3 MPa H2pressure at 270 °C for 4 h, which has been rarely reported on anisole transformation over heterogeneous catalysts so far. The characterizations results demonstrated that the H4Nb2O7modification reduced the slab length and stacking degree of MoS2during the hydrothermal process and enhanced the acidity property therefore improved the cleavage ability of CArO-CH3bond. This study provides a new scheme for the activity enhancement of MoS2in lignin demethylation, laying a foundation on the improvement of lignin utilization and the development of renewable energy strategy.
Photocatalytic synthesis of phenols mediated by visible light using KI as catalyst
Huiqin, Wei,Wu, Mei
supporting information, (2021/11/30)
A transition-metal-free hydroxylation of iodoarenes to afford substituted phenols is described. The reaction is promoted by KI under white LED light irradiation and uses atmospheric oxygen as oxidant. By the use of triethylamine as base and solvent, the corresponding phenols are obtained in moderate to good yields. Mechanistic studies suggest that KI and catalysis synergistically promote the cleavage of C-I bond to form free aryl radicals.