121-97-1Relevant articles and documents
Kinetic and product studies on the side-chain fragmentation of 1-arylalkanol radical cations in aqueous solution: Oxygen versus carbon acidity
Baciocchi, Enrico,Bietti, Massimo,Steenken, Steen
, p. 1785 - 1793 (1999)
A kinetic and product study of the side-chain fragmentation reactions of a series of 1-arylalkanol radical cations (4-MeOC6H4CH(OH)R?+) and some of their methyl ethers was carried out; the radical cations were generated by pulse radiolysis and γ radiolysis in aqueous solution. The radical cations undergo side-chain fragmentation involving the Cα-H and/or Cα-Cβ bonds, and their reactivity was studied both in acidic (pH ≤ 4) and basic (pH 10 - 11) solution. At pH 4, the radical cations decay with first-order kinetics, and the exclusive reaction is Cα-H deprotonation for 1?+, 2?+, and 3?+ (R = H, Me, and Et, respectively) but Cα-Cβ bond cleavage for 5?+, 6?+, and 7?+ (R = tBu, CH(OH)Me, and CH(OMe)Me, respectively). Both types of cleavage are observed for 4?+ (R = iPr). The radical cations of the methyl ethers 8?+, 9?+, and 10?+ (R = H, Et, and iPr, respectively) undergo exclusive deprotonation, whereas C-C fragmentation predominates for 11?+ (R = tBu). Large Cα deuterium kinetic isotope effects (4.5 and 5.0, respectively) were found for 1?+ and its methyl ether 8?+. Replacement of an α-OH group by OMe has a very small effect on the decay rate when the radical cation undergoes deprotonation, but a very large, negative effect in the case of C-C bond cleavage. It is suggested that hydrogen bonding of the α-OH group with the solvent stabilizes the transition state of the C-C bond fragmentation reaction but not that of the deprotonation process; however, other factors could also contribute to this phenomenon. The decay of the radical cations is strongly accelerated by HO-, and all the α-OH substituted radical cations react with HO- at a rate (≈1010M-1S-1) very close to the limit of diffusion control and independent of the nature of the bond that is finally broken in the process (C-H or C-C). The methyl ether 8?+, which exclusively undergoes C-H bond cleavage, reacts significantly slower (by a factor of ca. 50) than the corresponding alcohol 1?+. These data indicate that 1-arylalkanol radical cations, which display the expected carbon acidity in water, become oxygen acids in the presence of a strong base such as HO- and undergo deprotonation of the O-H group; diffusion-controlled formation of the encounter complex between HO- and the radical cation is the rate-deter- mining step of the reaction. It is sug- gested that, within the complex, the proton is transferred to the base to give a benzyloxyl radical, either via a radical zwitterion (which undergoes intramolecular electron transfer) or directly (electron transfer coupled with deprotonation). The latter possibility seems more in line with the general base catalysis (β ≈ 0.4) observed in the reaction of 5?+, which certainly involves O-H deprotonation. The benzyloxyl radical can then undergo a β C-C bond cleavage to form 4-methoxybenzalde-hyde and R? or a formal 1,2-H shift to form an a-hydroxybenzyl-type radical. The factors of importance in this carbon/ oxygen acidity dichotomy are discussed.
Triton X-100 functionalized Cu(II) dihydrazone based complex immobilized on Fe3O4@dopa: A highly efficient catalyst for oxidation of alcohols, alkanes, and sulfides and epoxidation of alkenes
Chakraborty, Tonmoy,Mondal, Rimpa,Ghanta, Rinku,Chakraborty, Aratrika,Chattopadhyay, Tanmay
, (2020)
Here, we have presented a protocol for green synthesis, characterization, and catalytic application of TX100/Fe3O4@dopa@CuL (FDCTX) magnetically separable nanoparticles. Fe3O4@dopa@CuL (FDC) was synthesized using a four-step procedure: (i) synthesis of a dihydrazone derivative, (ii) reaction of the dihydrazone derivative with copper perchlorate salt to generate a copper complex of the dihydrazone derivative, (iii) immobilization of the complex onto Fe3O4@dopa to generate FDC, and (iv) coating of FDC with surfactant Triton X-100. The as-synthesized homogeneous complex was well characterized using UV–Vis., Fourier-transform infrared (FT-IR), electrospray ionization–mass spectrometry, and single-crystalX-ray techniques. Single-crystalX-ray analysis revealed the tetranuclear framework of the complex. The heterogeneous nanoparticles (FDCTX) were characterized using FT-IR, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersiveX-ray spectroscopy, magnetic hysteresis, and dynamic light scattering techniques. Finally, both the homogeneous and heterogeneous catalysts were utilized for efficient oxidation of alcohols, alkanes, and sulfides and epoxidation of alkenes. A most probable mechanism for the oxidation reaction is proposed at the end of the article.
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Parke,Lawson
, p. 2871 (1941)
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Microwave-assisted acylation of aromatic compounds using carboxylic acids and zeolite catalysts
Yamashita, Hiroshi,Mitsukura, Yumi,Kobashi, Hiroko
, p. 80 - 86 (2010)
Acylation of aromatic compounds with carboxylic acids smoothly proceeded at 190-230 °C in the presence of zeolite catalysts under microwave irradiation to give aromatic ketones efficiently. H-Y (SiO2/Al2O 3 = 30-80) and H-beta (25) zeolites were active for the acylation reaction, giving the aromatic ketones in good yields. Carboxylic acids such as hexanoic and butyric acid smoothly underwent the acylation, while propionic acid showed somewhat lower reactivity. Anisole gave the para-acylation products nearly selectively. Anisole, 2,3-dihydrobenzofuran, and thiophene were reactive aromatic compounds. 2,3-Dihydrobenzofuran also reacted at the para position to the oxygen atom predominantly to give the corresponding ketones as the major products. The microwave reactions were generally faster than the conventional oil bath reactions and gave higher yields of the acylation products. Activation energies for the reaction of anisole with butyric acid by microwave and by oil bath heating were also estimated on the basis of the Arrhenius plots.
Direct Hydrodecarboxylation of Aliphatic Carboxylic Acids: Metal- and Light-Free
Burns, David J.,Lee, Ai-Lan,McLean, Euan B.,Mooney, David T.
supporting information, p. 686 - 691 (2022/01/28)
A mild and inexpensive method for direct hydrodecarboxylation of aliphatic carboxylic acids has been developed. The reaction does not require metals, light, or catalysts, rendering the protocol operationally simple, easy to scale, and more sustainable. Crucially, no additional H atom source is required in most cases, while a broad substrate scope and functional group tolerance are observed.
Development of Trifluoromethanesulfonic Acid-Immobilized Nitrogen-Doped Carbon-Incarcerated Niobia Nanoparticle Catalysts for Friedel-Crafts Acylation
Yang, Xi,Yasukawa, Tomohiro,Yamashita, Yasuhiro,Kobayashi, Shū
, p. 15800 - 15806 (2021/10/25)
Heterogeneous trifluoromethanesulfonic acid-immobilized nitrogen-doped carbon-incarcerated niobia nanoparticle catalysts (NCI-Nb-TfOH) that show excellent catalytic performance with low niobium loading (1 mol %) in Friedel-Crafts acylation have been developed. These catalysts exhibit higher activity and higher tolerance to catalytic poisons compared with the previously reported TfOH-treated NCI-Ti catalysts, leading to a broader substrate scope. The catalysts were characterized via spectroscopic and microscopic studies.
V2O5@TiO2 Catalyzed Green and Selective Oxidation of Alcohols, Alkylbenzenes and Styrenes to Carbonyls
Upadhyay, Rahul,Kumar, Shashi,Maurya, Sushil K.
, p. 3594 - 3600 (2021/07/02)
The versatile application of different functional groups such as alcohols (1° and 2°), alkyl arenes, and (aryl)olefins to construct carbon-oxygen bond via oxidation is an area of intense research. Here, we report a reusable heterogeneous V2O5@TiO2 catalyzed selective oxidation of various functionalities utilizing different mild and eco-compatible oxidants under greener reaction conditions. The method was successfully applied for the alcohol oxidation, oxidative scission of styrenes, and benzylic C?H oxidation to their corresponding aldehydes and ketones. The utilization of mild and eco-friendly oxidizing reagents such as K2S2O8, H2O2 (30 % aq.), TBHP (70 % aq.), broad substrate scope, gram-scale synthesis, and catalyst recyclability are notable features of the developed protocol.
