T:Toxic;
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.
Noble Metal Supported on Activated Carbon for “Hydrogen Free” HDO Reactions: Exploring Economically Advantageous Routes for Biomass Valorisation
Jin, Wei,Santos, José Luis,Pastor-Perez, Laura,Gu, Sai,Centeno, Miguel Angel,Reina, Tomas Ramirez
, p. 4434 - 4441 (2019)
An innovative route for bio-compounds upgrading via “hydrogen-free” hydrodeoxygenation (HDO) is proposed and evaluated using guaiacol as a model compound in a high-pressure batch reactor. Experimental results showed that noble metal supported on activated carbon catalysts are able to conduct tandem multiple steps including water splitting and subsequent HDO. The activity of Ru/C catalyst is superior to other studied catalysts (i. e. Au/C, Pd/C and Rh/C) in our water-only HDO reaction system. The greater dispersion and smaller metal particle size confirmed by the TEM micrographs accounts for the better performance of Ru/C. This material also presents excellent levels of stability as demonstrated in multiple recyclability runs. Overall, the proposed novel approach confirmed the viability of oxygenated bio-compounds upgrading in a water-only reaction system suppressing the need of external H2 supply and can be rendered as a fundamental finding for the economical biomass valorisation to produce added value bio-fuels.
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.
Kinetic analysis and reaction mechanism for anisole conversion over zirconia-supported molybdenum oxide
Shetty, Manish,Anderson, Eric M.,Green, William H.,Román-Leshkov, Yuriy
, p. 248 - 257 (2019)
Gas-phase catalytic conversion of anisole and its reaction intermediates was studied over a 10 wt% MoO3/ZrO2 catalyst at temperatures between 553 and 633 K and H2 partial pressures (PH2) ≤ 1 bar. Benzene, phenol, cresol and methyl anisole were identified as the primary products from the hydrodeoxygenation (HDO), hydrogenolysis, intra- and intermolecular alkylation of anisole, respectively. The anisole to benzene conversion featured a first-order dependence with respect to PH2, while the conversion of phenol to benzene and m-cresol to toluene, showed PH2 and Poxygenate reaction orders of 1/2 and zero, respectively. A kinetic model showed that although the secondary pathway of phenol HDO to benzene has a rate constant ～3 times higher than that for the HDO of anisole to benzene, the anisole HDO pathway is dominant at low anisole conversions. Apparent orders of ～? with Poxygenate for anisole hydrogenolysis and alkylation to form phenol, cresol, and methyl anisole implied the existence of different active sites than those responsible for HDO. Co-feed studies with H2O, pyridine, and di-tert butyl pyridine (DTBP) indicated that the active-sites responsible for HDO have a Lewis acid character that is associated with oxygen vacancies and that is distinct from the nature of sites responsible for hydrogenolysis and alkylation. Accordingly, co-feeding CH3OH resulted in increased phenol alkylation rates to form alkylated cresols along with inhibition of phenol to benzene HDO rates. A three-site model was proposed to unify the HDO, hydrogenolysis, and alkylation reactivity data obtained from the kinetic and co-feed studies.
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.
Influence of Re addition to Ni/SiO2 catalyst on the reaction network and deactivation during hydrodeoxygenation of m-cresol
Ge, Qingfeng,Han, Jinyu,Wang, Hua,Yang, Feifei,Zhu, Xinli
, p. 79 - 86 (2020)
The reaction network of hydrodeoxygenation of m-cresol was investigated over Ni/SiO2 and Ni-Re/SiO2 catalysts at 300 °C and 1 atm H2. m-Cresol conversion proceeds through three major primary pathways: phenyl ring hydrogenation to 3-methylcyclohexanone and 3-methylcyclohexanol, C[sbnd]C hydrogenolysis to CH4 and phenol, and deoxygenation to toluene. Re addition promotes dehydrogenation of the initially formed methylcyclohexanone and methylcyclohexanol to surface intermediates followed by deoxygenation toward formation of toluene. C[sbnd]C hydrogenolysis happens on unsaturated compounds with phenyl ring, instead of saturated compounds, since dehydrogenation is requested prior to C[sbnd]C cleavage. The turnover frequency (TOF) for CH4 formation follows the order of m-cresol 4. Re addition not only promotes deoxygenation to toluene by providing active Ni-Re neighboring sites, but also inhibits the aromatics hydrogenolysis to CH4, resulting in high toluene selectivity on bimetallic catalyst. Both catalysts show a similar deactivation trend and coke is speculated to be the major reason for deactivation.
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.
Selective conversion of m-cresol to toluene over bimetallic Ni-Fe catalysts
Nie, Lei,De Souza, Priscilla M.,Noronha, Fabio B.,An, Wei,Sooknoi, Tawan,Resasco, Daniel E.
, p. 47 - 55 (2014)
The catalytic conversion of m-cresol in the presence of H2 has been investigated on SiO2-supported Ni, Fe, and bimetallic Ni-Fe catalysts at 300 °C and atmospheric pressure. Over the monometallic Ni catalyst, the dominant product is 3-methylcyclohexanone while 3-methylcyclohexanol and toluene appear in smaller amounts, even at high conversions. By contrast, on Fe and Ni-Fe bimetallic catalysts, the dominant product is toluene while the hydrogenation products (3-methylcyclohexanone and 3-methylcyclohexanol) are practically negligible in the entire range of conversions. To explain these differences, we have proposed a deoxygenation path that starts with the tautomerization of m-cresol to an unstable ketone intermediate (3-methyl-3,5-cyclohexadienone). The fate of this intermediate is determined by the ability of the catalyst to either hydrogenate the carbonyl group or the ring. The former would mostly occur on Fe and Ni-Fe catalysts that contain an oxophilic metal (Fe), while the latter would occur on Ni, which has a higher affinity for the aromatic ring. Hydrogenation of the carbonyl group produces a very reactive unsaturated alcohol (3-methyl-3,5-cyclohexadienol), which can be easily dehydrated to toluene. This would explain the high selectivity of Fe and Ni-Fe to toluene. By contrast, hydrogenation of the ring would result in 3-methylcyclohexanone, which can be further hydrogenated to 3-methylcyclohexanol. On supports that contain acid sites, which are active for dehydration, the formation of toluene would occur via dehydration of the alcohol and subsequent dehydrogenation. On the catalysts investigated in this work, dehydration of the corresponding alcohol does not occur, so the only path to toluene is via hydrogenation of the carbonyl of the unstable ketone intermediate. In addition, to the products mentioned above, xylenol is also observed in significant yields, which indicate that transalkylation of m-cresol is another reaction path occurring on these catalysts.
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.
