732-26-3Relevant articles and documents
Phenol alkylation with isobutene - influence of heterogeneous Lewis and/or Bronsted acid sites
Modrogan, Elena,Valkenberg, Michael H.,Hoelderich, Wolfgang F.
, p. 177 - 187 (2009)
Acidic solid catalysts with different types of acidity were used to study the liquid-phase alkylation of phenol with isobutene. A phosphonium ionic liquid immobilized on silica type carrier exhibiting pure Lewis acidity, Amberlyst 15 with pure Bronsted acidity as well as WO3/ZrO2 with both types of acid sites were used for this study. The active sites are postulated based on pyridine-FT-IR and NH3-TPD studies, BET analyses, MAS NMR and XRD measurements. The different properties of the chosen catalysts are mirrored in the product distribution of the reaction mixture. It was found that WO3/ZrO2 is a very active and selective catalyst for the production of 2,4-di-tert-butylphenol under mild reaction conditions.
ACTIVITY OF SECONDARY AROMATIC AMINES AS CATALYSTS IN THE REACTION OF STERICALLY HINDERED AROXYL RADICALS WITH HYDROPEROXIDES
Varlamov, V. T.
, p. 482 - 490 (1989)
Secondary aromatic amines AmH catalyze the reaction of the 2,4,6-tri-t-butylphenoxyl radical ArO* with cumyl hydroperoxide ROOH.This effect is closely connected with the antioxidant action of the mixtures of sterically hindered phenols and AmH which have a synergistic effect and which are used in practice.The present work is directed to a study of the dependence of the catalytic activity of AmH on the temperature and on the substituents on the aromatic rings.
Multiple N-H and C-H Hydrogen Atom Abstractions through Coordination-Induced Bond Weakening at Fe-Amine Complexes
Wang, Zongheng,Johnson, Samantha I.,Wu, Guang,Ménard, Gabriel
, p. 8242 - 8251 (2021/06/25)
We report the use of the reported Fe-phthalocyanine complex, PcFe (1; Pc = 1,4,8,11,15,18,22,25-octaethoxy-phthalocyanine), to generate PcFe-amine complexes 1-(NH3)2, 1-(MeNH2)2, and 1-(Me2NH)2. Treatment of 1 or 1-(NH3)2 to an excess of the stable aryloxide radical, 2,4,6-tritert-butylphenoxyl radical (tBuArO?), under NH3 resulted in catalytic H atom abstraction (HAA) and C-N coupling to generate the product 4-amino-2,4,6-tritert-butylcyclohexa-2,5-dien-1-one (2) and tBuArOH. Exposing 1-(NH3)2 to an excess of the trityl (CPh3) variant, 2,6-di-tert-butyl-4-tritylphenoxyl radical (TrArO?), under NH3 did not lead to catalytic ammonia oxidation as previously reported in a related Ru-porphyrin complex. However, pronounced coordination-induced bond weakening of both α N-H and β C-H in the alkylamine congeners, 1-(MeNH2)2 and 1-(Me2NH)2, led to multiple HAA events yielding the unsaturated cyanide complex, 1-(MeNH2)(CN), and imine complex, 1-(MeN═CH2)2, respectively. Subsequent C-N bond formation was also observed in the latter upon addition of a coordinating ligand. Detailed computational studies support an alternating mechanism involving sequential N-H and C-H HAA to generate these unsaturated products.
Aryl phenol compound as well as synthesis method and application thereof
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Paragraph 0121-0124, (2021/05/12)
The invention discloses a synthesis method of an aryl phenol compound shown as a formula (3). All systems are carried out in an air or nitrogen atmosphere, and visible light is utilized to excite a photosensitizer for catalyzation. In a reaction solvent, ArNR1R2 as shown in a formula (1) and water as shown in a formula (2) are used as reaction raw materials and react under the auxiliary action of acid to obtain the aryl phenol compound as shown in a formula (3). The ArNR1R2 in the formula (1) can be primary amine and tertiary amine, can also be steroid and amino acid derivatives, and can also be drugs or derivatives of propofol, paracetamol, ibuprofen, oxaprozin, indomethacin and the like. The synthesis method has the advantages of cheap and easily available raw materials, simple reaction operation, mild reaction conditions, high reaction yield and good compatibility of substrate functional groups. The fluid reaction not only can realize amplification of basic chemicals, but also can realize amplification of fine chemicals, such as synthesis of drugs propofol and paracetamol. The invention has wide application prospect and use value.
Visible-Light-Enhanced Cobalt-Catalyzed Hydrogenation: Switchable Catalysis Enabled by Divergence between Thermal and Photochemical Pathways
Mendelsohn, Lauren N.,MacNeil, Connor S.,Tian, Lei,Park, Yoonsu,Scholes, Gregory D.,Chirik, Paul J.
, p. 1351 - 1360 (2021/02/01)
The catalytic hydrogenation activity of the readily prepared, coordinatively saturated cobalt(I) precatalyst, (R,R)-(iPrDuPhos)Co(CO)2H ((R,R)-iPrDuPhos = (+)-1,2-bis[(2R,5R)-2,5-diisopropylphospholano]benzene), is described. While efficient turnover was observed with a range of alkenes upon heating to 100 °C, the catalytic performance of the cobalt catalyst was markedly enhanced upon irradiation with blue light at 35 °C. This improved reactivity enabled hydrogenation of terminal, di-, and trisubstituted alkenes, alkynes, and carbonyl compounds. A combination of deuterium labeling studies, hydrogenation of alkenes containing radical clocks, and experiments probing relative rates supports a hydrogen atom transfer pathway under thermal conditions that is enabled by a relatively weak cobalt-hydrogen bond of 54 kcal/mol. In contrast, data for the photocatalytic reactions support light-induced dissociation of a carbonyl ligand followed by a coordination-insertion sequence where the product is released by combination of a cobalt alkyl intermediate with the starting hydride, (R,R)-(iPrDuPhos)Co(CO)2H. These results demonstrate the versatility of catalysis with Earth-abundant metals as pathways involving open-versus closed-shell intermediates can be switched by the energy source.
Visible light enables catalytic formation of weak chemical bonds with molecular hydrogen
Park, Yoonsu,Kim, Sangmin,Tian, Lei,Zhong, Hongyu,Scholes, Gregory D.,Chirik, Paul J.
, p. 969 - 976 (2021/07/25)
The synthesis of weak chemical bonds at or near thermodynamic potential is a fundamental challenge in chemistry, with applications ranging from catalysis to biology to energy science. Proton-coupled electron transfer using molecular hydrogen is an attractive strategy for synthesizing weak element–hydrogen bonds, but the intrinsic thermodynamics presents a challenge for reactivity. Here we describe the direct photocatalytic synthesis of extremely weak element–hydrogen bonds of metal amido and metal imido complexes, as well as organic compounds with bond dissociation free energies as low as 31 kcal mol?1. Key to this approach is the bifunctional behaviour of the chromophoric iridium hydride photocatalyst. Activation of molecular hydrogen occurs in the ground state and the resulting iridium hydride harvests visible light to enable spontaneous formation of weak chemical bonds near thermodynamic potential with no by-products. Photophysical and mechanistic studies corroborate radical-based reaction pathways and highlight the uniqueness of this photodriven approach in promoting new catalytic chemistry. [Figure not available: see fulltext.].
Method for synthesizing 2, 4 and 6 -tert-butylphenol
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Paragraph 0032-0082, (2021/11/14)
The invention belongs to the technical field of organic synthesis, and particularly relates to a method for synthesizing 2, 4 and 6 - tri-tert-butylphenol, which comprises the following steps: 1) adding phenol, a catalyst, demineralized water, heating and stirring. 2) To the isobutene, maintain temperature pressure, stirring. 3) Aqueous sodium carbonate aqueous solution, neutralization reaction, washing of the oil phase, separation of the oil phase and the aqueous phase. 4) The oil phase is rectified, and a reaction intermediate product is obtained at the top of the tower, which is used as a reaction material for the next kettle reaction to continue to be alkylated. 2, 4 and 6 -tert-butylphenol crude product is obtained in the tower kettle. 5) The crude product was recrystallized and dried with ethanol as a solvent to give 2, 4, 6 -tert-butylphenol product. The synthesis method provided by the invention is scientific and reasonable in design, adopts micro negative pressure pressure conditions as reaction pressure conditions, effectively avoids the self-polymerization phenomenon of isobutene, is mild and controllable in overall reaction conditions, and is low in reaction temperature, free of byproducts and high in product purity.
A Bioinspired Disulfide/Dithiol Redox Switch in a Rhenium Complex as Proton, H Atom, and Hydride Transfer Reagent
Hua, Shao-An,Paul, Lucas A.,Oelschlegel, Manuel,Dechert, Sebastian,Meyer, Franc,Siewert, Inke
supporting information, p. 6238 - 6247 (2021/05/07)
The transfer of multiple electrons and protons is of crucial importance in many reactions relevant in biology and chemistry. Natural redox-active cofactors are capable of storing and releasing electrons and protons under relatively mild conditions and thus serve as blueprints for synthetic proton-coupled electron transfer (PCET) reagents. Inspired by the prominence of the 2e-/2H+ disulfide/dithiol couple in biology, we investigate herein the diverse PCET reactivity of a Re complex equipped with a bipyridine ligand featuring a unique SH···-S moiety in the backbone. The disulfide bond in fac-[Re(S-Sbpy)(CO)3Cl] (1, S-Sbpy = [1,2]dithiino[4,3-b:5,6-b′]dipyridine) undergoes two successive reductions at equal potentials of-1.16 V vs Fc+|0 at room temperature forming [Re(S2bpy)(CO)3Cl]2- (12-, S2bpy = [2,2′-bipyridine]-3,3′-bis(thiolate)). 12- has two adjacent thiolate functions at the bpy periphery, which can be protonated forming the S-H···-S unit, 1H-. The disulfide/dithiol switch exhibits a rich PCET reactivity and can release a proton (G°H+ = 34 kcal mol-1, pKa = 24.7), an H atom (? G°H = 59 kcal mol-1), or a hydride ion (G°H- = 60 kcal mol-1) as demonstrated in the reactivity with various organic test substrates.
Electron-rich phenoxyl mediators improve thermodynamic performance of electrocatalytic alcohol oxidation with an iridium pincer complex
Galvin, Conor M.,Waymouth, Robert M.
supporting information, p. 19368 - 19378 (2020/12/01)
Electron-rich phenols, including α-rac-tocopherol Ar1OH, 2,4,6,-tri-tert-butylphenol Ar3OH, and butylated hydroxy-toluene Ar4OH, are effective electrochemical mediators for the electrocatalytic oxidation of alcohols by an iridium amido dihyride complex (PNP)Ir(H)2 (IrN 1, PNP = bis[2-diisopropylphosphino)ethyl]amide). Addition of phenol mediators leads to a decrease in the onset potential of catalysis from -0.65 V vs Fc+/0 under unmediated conditions to -1.07 V vs Fc+/0 in the presence of phenols. Mechanistic analysis suggests that oxidative turnover of the iridium amino trihydride (PNHP)Ir(H)3 (IrH 2, PNHP = bis[2-diisopropylphosphino)ethyl]amine) to IrN 1 proceeds through two successive hydrogen atom transfers (HAT) to 2 equiv of phenoxyl that are generated transiently at the anode. Isotope studies and comparison to known systems are consistent with initial homolysis of an Ir-H bond being rate-determining. Turnover frequencies up to 14.6 s-1 and an average Faradaic efficiency of 93% are observed. The mediated system shows excellent chemoselectivity in bulk oxidations of 2-propanol and 1,2-benzenedimethanol in THF and is also viable in neat 2-propanol.
Coordination-Induced N-H Bond Weakening in a Molybdenum Pyrrolidine Complex: Isotopic Labeling Provides Insight into the Pathway for H2Evolution
Bezdek, Máté J.,Pelczer, István,Chirik, Paul J.
supporting information, p. 3050 - 3059 (2020/09/02)
The synthesis and characterization of a cationic molybdenum pyrrolidine complex are described that exhibits significant coordination-induced N-H bond weakening. The N-H bond dissociation free energy (BDFE) of the coordinated pyrrolidine in [(PhTpy)(PPh2Me)2Mo(NH(pyrr))][BArF24] ([1-NH(pyrr)]+PhTpy = 4′-Ph-2,2′,6′,2″-terpyridine, NH(pyrr) = pyrrolidine, ArF24 = [C6H3-3,5-(CF3)2]4) was determined to be between 41 and 51 kcal mol-1 by thermochemical analysis and supported by a density functional theory (DFT) computed value of 48 kcal mol-1. The complex [1-NH(pyrr)]+ underwent proton-coupled electron transfer (PCET) to 2,4,6-tri-tert-butylphenoxyl radical, as well as spontaneous H2 evolution upon gentle heating to furnish the corresponding molybdenum pyrrolidide complex [(PhTpy)(PPh2Me)2Mo(N(pyrr))][BArF24] ([1-N(pyrr)]+). Thermolysis of the deuterated isotopologue [1-ND(pyrr)]+ still produced H2 with concomitant incorporation of the isotopic label into the pyrrolidide ligand in the product [(1-N(pyrr-dn)]+ (n = 0-2), consistent with an H2 evolution pathway involving intramolecular H-H bond formation followed by an intermolecular product-forming PCET step. These observations provide the context for understanding H2 evolution in the nonclassical ammine complex [(PhTpy)(PPh2Me)2Mo(NH3)][BArF24] ([1-NH3]+) and are supported by DFT-computed reaction thermochemistry. Overall, these studies offer rare insight into the H2 formation pathway in nonclassical amine complexes with N-H BDFEs below the thermodynamic threshold for H2 evolution and inform the development of well-defined, thermodynamically potent PCET reagents.
