1122-54-9Relevant articles and documents
Metal- and radical-free aerobic oxidation of heteroaromatic methanes: An efficient synthesis of heteroaromatic aldehydes
Ye, Rongzi,Cao, Yuanjie,Xi, Xiaoxiang,Liu, Long,Chen, Tieqiao
, p. 4220 - 4224 (2019)
A metal-free and radical-free synthesis of heteroaromatic aldehydes was developed through aerobic oxidation of methyl groups in an I2/DMSO/O2 catalytic system. Under the reaction conditions, various functional groups such as methoxy, aldehyde, ester, nitro, amide, and halo (F, Cl, Br) groups were well tolerated. The bioactive compounds like chlorchinaldin derivative and papaverine were also oxidized to the corresponding aldehydes and ketones. This reaction provided an efficient method for preparing the valuable heteroaromatic aldehydes.
Aerobic oxidation of secondary pyridine-derivative alcohols in the presence of carbon-supported noble metal catalysts
Frassoldati, Antonio,Pinel, Catherine,Besson, Michèle
, p. 133 - 138 (2013)
Pt/C and PtBi/C catalysts prepared on a synthetic mesoporous carbon were evaluated in the oxidation of secondary aromatic alcohols (1-phenylethanol, α-methyl or phenyl pyridinemethanol) with air in different dioxane/water mixtures at 100 °C under 10 bar air. The observed activity for all substrates over both types of catalysts was strongly improved with the addition of water to the dioxane solvent as a result of different interactions of the alcohols with the metallic surface in the apolar dioxane solvent or polar aqueous medium. A promoting effect of bismuth was observed for all substrates. However, the reaction rate was also dramatically influenced by the nature of the aromatic moiety, the nature of the α-group, and the position of the substituent on the pyridine moiety. As a general rule the reactivity was meta para ortho and the pyridine derivatives with a phenyl group were more reactive. α-Phenyl-2-pyridinemethanol was totally converted to 2-benzoylpyridine with a selectivity of 96% in dioxane/water 50/50 vol% in the presence of a 2.7% Pt-0.9% Bi/C. Nevertheless, platinum leaching was detected, which could be limited with the promotion by bismuth.
Chain mechanism in the photocleavage of phenacyl and pyridacyl esters in the presence of hydrogen donors
Literak, Jaromir,Dostalova, Anna,Klan, Petr
, p. 713 - 723 (2006)
Excited phenacyl and 3-pyridacyl esters of benzoic acid react with an excess of aliphatic alcohols in a chain reaction process involving hydrogen transfer from the ketyl radical intermediates, leading to benzoic acid in addition to acetophenone and 3-acetylpyridine, respectively, as the byproducts. While the maximum quantum yields reached 4 in both cases, the 2- or 4-pyridacyl ester photoreduction proceeded with the efficiency below 100% under the same conditions. The investigation indicates that a radical coupling between ketyl radicals, both formed from the excited ester by hydrogen abstraction from an alcohol, is accompanied by the elimination of benzoic acid from the ester ketyl radical itself. A partitioning between two reactions was found to be remarkably sensitive to the chromophore nature, such as a position of the nitrogen atom in the pyridacyl moiety, The magnitude of a radical chain process is dependent on the efficiency of consecutive steps that produce free radicals capable of a subsequent ester reduction. The driving force of a possible electron transfer from the ketyl radicals to the ester has been excluded on the basis of cyclic voltametry measurements. The observed quantum yields of photoreduction were found to be diminished by formation of relatively long-lived light absorbing transients, coproducts obtained apparently by secondary photochemical reactions. Additionally, it is shown that basic additives such as pyridine can further increase the efficiency of the photoreduction by a factor of 4. A radical nature of the reduction mechanism was supported by finding a large kinetic chain length of an analogous reaction initiated by free radicals generated thermally yet again when phenacyl or 3-pyridacyl benzoate was used. Both phenacyl and pyridacyl chromophores are pronounced to be valuable as the photoremovable protecting groups when high quantum and chemical yields of carboxylic acid elimination are important, but higher concentrations of the hydrogen atom donors are not destructive for a reaction system or are experimentally impractical.
Transition-Metal-Free Oxidation of Benzylic C-H Bonds of Six-Membered N-Heteroaromatic Compounds
Gao, Xianying,Han, Shuaijun,Zheng, Maolin,Liang, Apeng,Zou, Dapeng,Wu, Yusheng,Wu, Yangjie,Li, Jingya
, p. 4040 - 4049 (2019)
A novel oxidation of benzylic C-H bonds for the synthesis of diverse six-membered N-heteroaromatic aldehydes and ketones has been developed. The obvious advantages of this approach are the simple operation, mild reaction conditions, and without use of toxic reagent and transition metal. The present method should provide a useful access for the synthesis and modification of N-heterocycles.
Methyltrichlorosilane as an effective activation agent for swern oxidation
Wang, Yuanxun,Wang, Chao,Sun, Jian
, p. 2961 - 2965 (2014)
A practical and efficient alternative version of the Swern oxidation has been successfully developed. Methyltrichlorosilane was used as an efficient activator of dimethylsulfoxide, which could oxidize a wide range of primary and secondary alcohols to the corresponding carbonyl compounds with good to excellent yields.
Time-Resolved EPR Studies on the Photochemical Hydrogen Abstraction Reactions and the Excited Triplet States of 4-Substituted Pyridines
Tero-Kubota, Shozo,Akiyama, Kimio,Ikoma, Tadaaki,Ikegami, Yusaku
, p. 766 - 770 (1991)
Photochemical hydrogen abstraction reactions and the lowest excited triplet states taking part in the initial process have been investigated for several pyridine derivatives by using the time-resolved EPR-method.The emissive CIDEP spectrum obtained from the laser photolysis of 4-acetylpyridine (1) in 2-propanol was assigned to the corresponding ketyl radical, proving initial hydrogen abstraction by the carbonyl group.In the cases of 4-cyano-(2) and 4-methoxycarbonyl-(3) pyridines, and 4-pyridinecarboxamide (4), enhanced absorptive CIDEP spectra due to the corresponding 1-hydropyridinyl radicals were observed, suggesting the preferential population to the lowest sublevel in the intersystem crossing.The triplet EPR and phosphorescence spectra observed at 77 K indicate that T1 of 1 is mainly the carbonyl n?* state with small contribution from the ??* state.The T1 states of 2,3, and 4 are considered to be of mixed character between the pyridine 3B1(n?*) and 3A1(??*)states, though the interaction is smaller than that of unsubstituted pyridine because of raising of the ??* state by electron-withdrawing groups.It is proposed that the T1 states of 2-4 have smaller deviation from the planar conformation than the T1 state of unsubstituted pyridine.
Microwave assisted conversion of oximes and semicarbazones to carbonyl compounds using benzyltriphenylphosphonium peroxymonosulfate
Hajipour, Abdol R.,Mallakpour, Shadpour E.,Mohammadpoor-Baltork, Iraj,Adibi, Hadi
, p. 45 - 49 (2003)
Benzyltriphenylphosphonium peroxymonosulfate in the presence of catalytic amounts of bismuth chloride was found to be an efficient and mild reagent for the oxidative cleavage of oximes and semicarbazones to the corresponding carbonyl compounds under microwave irradiation.
Formate-driven catalysis and mechanism of an iridium-copper complex for selective aerobic oxidation of aromatic olefins in water
Shimoyama, Yoshihiro,Kitagawa, Yasutaka,Ohgomori, Yuji,Kon, Yoshihiro,Hong, Dachao
, p. 5796 - 5803 (2021)
A hetero-dinuclear IrIII-CuIIcomplex with two adjacent sites was employed as a catalyst for the aerobic oxidation of aromatic olefins driven by formate in water. An IrIII-H intermediate, generated through formate dehydrogenation, was revealed to activate terminal aromatic olefins to afford an Ir-alkyl species, and the process was promoted by a hydrophobic [IrIII-H]-[substrate aromatic ring] interaction in water. The Ir-alkyl species subsequently reacted with dioxygen to yield corresponding methyl ketones and was promoted by the presence of the CuIImoiety under acidic conditions. The IrIII-CuIIcomplex exhibited cooperative catalysis in the selective aerobic oxidation of olefins to corresponding methyl ketones, as evidenced by no reactivities observed from the corresponding mononuclear IrIIIand CuIIcomplexes, as the individual components of the IrIII-CuIIcomplex. The reaction mechanism afforded by the IrIII-CuIIcomplex in the aerobic oxidation was disclosed by a combination of spectroscopic detection of reaction intermediates, kinetic analysis, and theoretical calculations.
Elemental selenium reactions with 4-ethylpyridine
Gleich, Edward,Warnke, Zygmunt
, p. 13 - 28 (1998)
A reaction of elemental selenium with 4-ethylpyridine has been studied. The process was run in sealed ampuls, within 205 - 240°C, under nitrogen. The reaction products were indentified by GC-MS and 1H NMR. The following products have been identified: (4-pyridyl)hydroxymethyl ketone, (4-pyridyl)methyl ketone, (4-pyridyl)-hydroselenomethyl ketone, 2,3-di(4-pyridyl)butane, 1,3-di(4-pyridyl)butane, 1-(4-pyridyl)-1-[2-(4-ethyl)pyridyl]-ethane, 1-(4-pyridyl)-1-[2-(4-ethenyl)pyridyl]ethane.
Reaction of 3,5-disubstituted 4,5-dihydroisoxazoles with hexacarbonylmolybdenum
Koroleva,Katok,Lakhvich
, p. 1003 - 1008 (2004)
Depending on the reaction conditions and structure of the 5-substituent, reactions of substituted 4,5-dihydroisoxazoles with hexacarbonylmolybdenum involve cleavage of the heteroring at the N-O bond, its aromatization, or/and 1,3-decyclization.