2819-86-5Relevant academic research and scientific papers
Acid-Catalyzed Rearrangements of the Epoxides of Hexamethylbicyclohepta-2,5-dienone
Hart, Harold,Chen, Sun-Mao,Lee, Shin
, p. 2096 - 2099 (1980)
Epoxy enone 1 rearranges in trifluoroacetic acid (TFA) at 0 deg C to hexamethyl-8-oxabicycloocta-3,6-dien-2-one (3).A mechanism involving initial protonation of the carbonyl oxygen of 1, cleavage of the C-C bond of the epoxide ring, and the intermediacy of a dicyclopropylcarbinyl-type carbocation intermediate is suggested and supported by deuterium labeling.Epoxy enone 2 rearranges in TFA at 0 deg C to give products containing the TFA moiety in a form not easily hydrolyzed by base.The products have a structure with a plane of symmetry and are thought to be stereoisomers containing a 7-norbornenone skeleton and an ortho ester type of moiety (5).A mechanism involving intramolecular trapping of a carbocation by neighboring trifluoroacetate is suggested to explain the results.Pyrolysis of 3 (500 deg C) gives pentamethylphenol.
Selective C-C bond cleavage of amides fused to 8-aminoquinoline controlled by a catalyst and an oxidant
Li, Sen,Jie, Kun,Yan, Wenjie,Pan, Qingjun,Zhang, Min,Wang, Yufeng,Fu, Zhengjiang,Guo, Shengmei,Cai, Hu
supporting information, p. 13820 - 13823 (2020/11/18)
Herein, copper-catalyzed direct C-C bond cleavage of amides fused to 8-aminoquinoline as a directing group to form urea in the presence of amines and dioxygen is reported. Compared to the previous C-H aminations of amides via C-H activation, this reaction presents a catalyst and oxidant controlled C-C bond cleavage strategy that enables amidation through a radical process. CuBr/Ag2CO3/O2 shows the best catalytic result at 150 °C. A series of aryl and alkyl amides were compatible with this transformation. Notably, this method provided access to cyclohexanone, one of the most important industrial materials. The pathway of this reaction was investigated.
CYCLIC PEROXIDE OXIDATION OF AROMATIC COMPOUND PRODUCTION AND USE THEREOF
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Page/Page column 9; 10, (2014/10/15)
The present invention provides a method for converting an aromatic hydrocarbon to a phenol by providing an aromatic hydrocarbon comprising one or more aromatic C-H bonds and one or more activated C-H bonds in a solvent; adding a phthaloyl peroxide to the solvent; converting the phthaloyl peroxide to a di-radical; contacting the di-radical with the one or more aromatic C-H bonds; oxidizing selectively one of the one or more aromatic C-H bonds in preference to the one or more activated C-H bonds; adding a hydroxyl group to the one of the one or more aromatic C-H bonds to form one or more phenols; and purifying the one or more phenols.
A protocol to generate phthaloyl peroxide in flow for the hydroxylation of arenes
Eliasen, Anders M.,Thedford, Randal P.,Claussen, Karin R.,Yuan, Changxia,Siegel, Dionicio
supporting information, p. 3628 - 3631 (2014/08/05)
A flow protocol for the generation of phthaloyl peroxide has been developed. This process directly yields phthaloyl peroxide in high purity (>95%) and can be used to bypass the need to isolate and recrystallize phthaloyl peroxide, improving upon earlier batch procedures. The flow protocol for the formation of phthaloyl peroxide can be combined with arene hydroxylation reactions and provides a method for the consumption of peroxide as it is generated to minimize the accumulation of large quantities of peroxide.
Metal-free oxidation of aromatic carbon-hydrogen bonds through a reverse-rebound mechanism
Yuan, Changxia,Liang, Yong,Hernandez, Taylor,Berriochoa, Adrian,Houk, Kendall N.,Siegel, Dionicio
, p. 192 - 196 (2013/08/23)
Methods for carbon-hydrogen (C-H) bond oxidation have a fundamental role in synthetic organic chemistry, providing functionality that is required in the final target molecule or facilitating subsequent chemical transformations. Several approaches to oxidizing aliphatic C-H bonds have been described, drastically simplifying the synthesis of complex molecules. However, the selective oxidation of aromatic C-H bonds under mild conditions, especially in the context of substituted arenes with diverse functional groups, remains a challenge. The direct hydroxylation of arenes was initially achieved through the use of strong Bronsted or Lewis acids to mediate electrophilic aromatic substitution reactions with super-stoichiometric equivalents of oxidants, significantly limiting the scope of the reaction. Because the products of these reactions are more reactive than the starting materials, over-oxidation is frequently a competitive process. Transition-metal-catalysed C-H oxidation of arenes with or without directing groups has been developed, improving on the acid-mediated process; however, precious metals are required. Here we demonstrate that phthaloyl peroxide functions as a selective oxidant for the transformation of arenes to phenols under mild conditions. Although the reaction proceeds through a radical mechanism, aromatic C-H bonds are selectively oxidized in preference to activated-H bonds. Notably, a wide array of functional groups are compatible with this reaction, and this method is therefore well suited for late-stage transformations of advanced synthetic intermediates. Quantum mechanical calculations indicate that this transformation proceeds through a novel addition-abstraction mechanism, a kind of 'reverse-rebound' mechanism as distinct from the common oxygen-rebound mechanism observed for metal-oxo oxidants. These calculations also identify the origins of the experimentally observed aryl selectivity.
Synthesis of polyalkylphenyl prop-2-ynoates and their flash vacuum pyrolysis to polyalkylcyclohepta[b]furan-2(2H)-ones
Nagel, Matthias,Hansen, Hans-Juergen
, p. 1022 - 1048 (2007/10/03)
A new method for the smooth and highly efficient preparation of polyalkylated aryl propiolates has been developed. It is based on the formation of the corresponding aryl carbonochloridates (cf Scheme 1 and Table 1) that react with sodium (or lithium) propiolate in THF at 25-65°, with intermediate generation of the mixed anhydrides of the arylcarbonic acids and prop-2-ynoic acid, which then decompose almost quantitatively into CO2 and the aryl propiolates (cf. Scheme 11). This procedure is superior to the transformation of propynoic acid into its difficult-to-handle acid chloride, which is then reacted with sodium (or lithium) arenolates. A number of the polyalkylated aryl propiolates were subjected to flash vacuum pyrolysis (FVP) at 600-650°and 10-2 Torr which led to the formation of the corresponding cyclohepta[b]furan-2(2H)-ones in average yields of 25-45% (cf. Scheme 14). It has further been found in pilot experiments that the polyalkylated cyclohepta[b]furan-2(2H)-ones react with 1-(pyrrolidin-1-yl)cyclohexene in toluene at 120-130°to yield the corresponding 1,2,3,4- tetrahydrobenz[a]azulenes, which become, with the growing number of Me groups at the seven-membered ring, more and more sensitive to oxidative destruction by air (cf. Scheme 15).
The Baeyer-Villiger Oxidation of Aromatic Aldehydes and Ketones with Hydrogen Peroxide Catalyzed by Selenium Compounds
Syper, Ludwik
, p. 167 - 172 (2007/10/02)
A series of organoselenium compounds was investigated as activators of hydrogen peroxide in the Baeyer-Villiger oxidation.As a result, a convenient and cheap method for transformation of aromatic aldehydes, having polycondensed ring systems or electron-donating substituents, and polymethoxy derivatives of acetophenone, into phenols was elaborated.This method utilizes hydrogen peroxide activated by areneseleninic acids, as oxidizing agent.
A quantitative examination of the photoisomerization of some protonated phenols
Childs, Ronald F.,George, Baha E.
, p. 1343 - 1349 (2007/10/02)
The photoisomerization of a series of protonated, methyl substituted phenols to protonated bicyclohexenones has been examined.These reactions, which were carried out in CF3SO3H as a strong acid solvent at ambient temperatures, provide a convenient route to a variety of bicyclohexenones.The quantum yields for these photoisomerizations vary from 0.018 for protonated 3,5-dimethylphenol to 0.65 for protonated 2,6-dimethylphenol.This variation in efficiency can be understood in terms of a competition between ring opening, to regenerate the starting phenol, or cyclopropyl migration, to give product, of aninitially formed intermediate.
Thermal isomerizations of protonated bicyclohexenones
Childs, Ronald F.,George, Baha E.
, p. 1350 - 1354 (2007/10/02)
The thermal isomerizations of a wide range of protonated methyl substituted bicyclohex-3-en-2-ones to protonated phenols has been examined using triflic acid as a strong acid solvent.The rate constants and activation energies of these isomerization has been determined.The barriers to the isomerizations were shown to be dependent on the number and position of the methyl substituents.The results show that three different mechanisms are needed to account for these isomerizations, two of which involve a preliminary circumambulatory rearrangement prior to ring opening and the other process involving a direct ring opening of the initial protonated bicyclohexenone to give an intermediate meta-protonated phenol.
REACTION OF 1,2,4-TRIMETHYLBENZENE WITH PERACETIC ACID
Kharchuk, V. G.,Kolenko, I. P.,Petrov, L. A.,Gus'kova, L. M.
, p. 2071 - 2078 (2007/10/02)
The oxidation of 1,2,4-trimethylbenzene with peracetic acid leads to the formation of trimethylphenols and hydroquinones, which undergo transformations to the corresponding benzoquinones and products from oxidative cleavage of the ring.The controlling stage of the process is the electrophilic hydroxylation of 1,2,4-trimethylbenzene.
