- Direct Acetoxylation of Arenes
-
Acetoxylation of arenes is an important reaction and an unmet need in chemistry. We report a metal-free, direct acetoxylation reaction using sodium nitrate under an anhydrous environment of trifluoroacetic acid, acetic acid, and acetic anhydride. Arenes (31 examples), with oxidation potentials (Eox, in V vs SCE) lower than benzene (2.48 V), were acetoxylated with good yields and regioselectivity. A stepwise, single electron-transfer mechanism is proposed.
- Hong Nguyen, Thi Anh,Hou, Duen-Ren
-
supporting information
p. 8127 - 8131
(2021/08/23)
-
- Regioselective Baeyer-Villiger oxidation of lignin model compounds with tin beta zeolite catalyst and hydrogen peroxide
-
Lignin depolymerization represents a promising approach to the sustainable production of aromatic molecules. One potential approach to the stepwise depolymerization of lignin involves oxidation of the benzylic alcohol group in β-O-4 and β-1 linkages, followed by Baeyer-Villiger oxidation (BVO) of the resulting ketones and subsequent ester hydrolysis. Towards this goal, BVO reactions were performed on 2-adamantanone, a series of acetophenone derivatives, and lignin model compounds using a tin beta zeolite/hydrogen peroxide biphasic system. XRD, 119Sn MAS NMR spectroscopy, DRUVS and XPS were used to determine tin speciation in the catalyst, the presence of both framework Sn and extra framework SnO2 being inferred. Conversion of ketones to BVO products was affected by electron donation as well as steric hindrance, 4′-methoxyacetophenone affording the highest yield of ester (81%). As the size and complexity of the ketone increased, excess hydrogen peroxide was typically needed for successful BVO. Yields of ester products derived from β-O-4 and β-1 lignin models were modest due to the formation of polymeric material stemming from direct ring hydroxylation.
- Jennings, John A.,Parkin, Sean,Munson, Eric,Delaney, Sean P.,Calahan, Julie L.,Isaacs, Mark,Hong, Kunlun,Crocker, Mark
-
p. 25987 - 25997
(2017/07/07)
-
- The Baeyer-Villiger oxidation versus aromatic ring hydroxylation: Competing organic peracid oxidation mechanisms explored by multivariate modelling of designed multi-response experiments
-
Peroxy acids can be used as the terminal oxidant for the Baeyer-Villiger oxidation of acetophenones and for direct ring hydroxylation of methoxy-substituted benzenes. An oxidative system involving 3-chloroperbenzoic acid (mCPBA) and 2,6-dimethoxyacetophenone as model substrate was investigated by means of statistical experimental design, multivariate modelling and response surface methodology. The outcome of the organic peracid oxidation experiments was portrayed by a multi-response matrix consisting of the yields of three different compounds; 2,6-dimethoxyphenyl acetate, 1-(4-hydroxy-2,6-dimethoxy-phenyl)ethanone and 3-hydroxy-2,6-dimethoxy-phenyl acetate. The optimized reaction protocol was utilized to investigate a series of various substituted acetophenones. The overall investigation revealed that both the molecular structure of the acetophenone substrate and the experimental conditions exhibited a substantial impact on whether the oxidation reaction follows the oxygen insertion or direct ring hydroxylation mechanism. An improved protocol for the direct ring hydroxylation was also obtained from the experimental and modelling described herein.
- Gambarotti, Cristian,Bj?rsvik, Hans-René
-
p. 619 - 628
(2015/09/28)
-
- Porous coordination polymers of diverse topologies based on a twisted tetrapyridylbiaryl: Application as nucleophilic catalysts for acetylation of phenols
-
Porous coordination polymers (CPs) with partially uncoordinated pyridyl rings based on rationally designed polypyridyl linkers are appealing from the point of view of their application as nucleophilic catalysts. A D2d--symmetric tetradentate organic linker L, that is, 2,2 ',6,6'-tetramethoxy-3,3',5,5'-tetrakis(4-pyridyl)biphenyl, was designed and synthesized for metal-assisted self-assembly aimed at porous CPs. Depending on the nature of the metal ion and the counter anion, the ligand L is found to function as a 3- or 4-connecting building block leading to porous CPs of diverse topologies. The reaction of L with Zn(NO3)2 and Cd(NO3)2 yields porous 2D CPs of "fes" topology, in which the tetrapyridyl linker L serves as a 3-connecting unit with its free pyridyl rings well exposed into the pores. The functional utility of these porous CPs containing uncoordinated pyridyl rings is demonstrated by employing them as efficient heterogeneous nucleophilic catalysts for acetylation of a number of phenols with varying electronic properties and reactivities.
- Seth, Saona,Venugopalan, Paloth,Moorthy, Jarugu Narasimha
-
p. 2241 - 2249
(2015/01/30)
-
- Rh-Catalyzed Synthesis of Coumarin Derivatives from Phenolic Acetates and Acrylates via C-H Bond Activation
-
An efficient annulation strategy involving the reaction of phenolic acetates with acrylates in the presence of [Rh2(OAc)4] as catalyst and formic acid as reducing agent, leading to the high yield synthesis of coumarin derivatives, has been developed. The addition of NaOAc as a base increased the yield of the products. The reaction is quite successful for both electron-rich as well as electron-deficient phenolic acetates, affording coumarins with excellent regioselectivity, and proceeds via C-H bond activation proven by deuterium incorporation studies.
- Gadakh, Sunita K.,Dey, Soumen,Sudalai, Arumugam
-
p. 11544 - 11550
(2015/12/04)
-
- Direct oxidation of secondary alcohol to ester by performic acid
-
The reaction pathways and kinetics of the oxidation reactions of 1-phenylethyl alcohol (PEA), 1-(3,4-dimethoxyphenyl)ethanol (MVA), 1-(4-hydroxy-3-methoxyphenyl)ethanol (HMOPE), 1-(3-aminophenyl)ethanol (APE), 1-(4-methylphenyl)ethanol (MPE) and cyclohexanol with performic acid (PFA) were investigated in formic acid solvent. An unexpected new reaction pathway, from which the secondary alcohols can be directly oxidized to corresponding esters, was found. The reaction products (esters and ketones) of oxidation of PEA, MVA, HMOPE, APE, MPE and cyclohexanol were detected at different reaction times. The reaction rate constants, k1, k2, k3 and power orders α, β, γ of PFA concentration for three oxidation reactions pathways: alcohol to ester, alcohol to ketone and ketone to ester were obtained, respectively. These findings might provide a new insight into the technology of lignin degradation.
- Li, Xiao-Hong,Meng, Xiang-Guang,Liu, Ying,Peng, Xiao
-
p. 3332 - 3336
(2013/12/04)
-
- Steric control of site selectivity in the Pd-catalyzed C-H acetoxylation of simple arenes
-
This report describes the use of an oxidant and a ligand to control site selectivity in the Pd(OAc)2-catalyzed C-H acetoxylation of simple arenes. The use of MesI(OAc)2 as the terminal oxidant in combination with acridine as the ligand results in primarily sterically controlled selectivity. In contrast, with Pd(OAc)2 as the catalyst and PhI(OAc)2 as the oxidant, electronic effects dominate the selectivity of arene C-H acetoxylation.
- Cook, Amanda K.,Emmert, Marion H.,Sanford, Melanie S.
-
supporting information
p. 5428 - 5431
(2013/11/19)
-
- Palladium-catalyzed acetoxylation of arenes by novel sulfinyl n-heterocyclic carbene ligand complexes
-
A series of novel ligands based on N-heterocyclic carbene and sulfoxide functionalities have been prepared and characterized. Pd(II) complexes have been synthesized by transmetalation from the corresponding NHC-Ag derivatives, and their behavior as catalysts has been studied in arene C-H bond oxidative activation. Studies conducted toward the elucidation of the reaction mechanism of the acetoxylation suggest a C-H activation step at Pd(IV) rather than Pd(II) intermediates.
- Tato, Francisco,Garcia-Dominguez, Andres,Cardenas, Diego J.
-
supporting information
p. 7487 - 7494
(2014/04/03)
-
- Theoretical and experimental studies on selective oxidation of aromatic ketone by performic acid
-
The Baeyer-Villiger (B-V) reactions of 3,4-dimethoxy acetophenone (DMOAP), 4-methyl acetophenone (MAP), and acetophenone (AP) with performic acid (PFA) in formic acid (FA) solvent have been studied by density functional theory (DFT) method. The noncatalyzed and the formic acid-catalyzed reaction paths have been calculated at the MPWB1K/6-311++G(d,p)-IEF-PCM// MPWB1K/6-311G(d,p) level of theory. On the basis of the calculations, the attack of peracid to the carbonyl carbon is rate-determining in both the noncatalyzed and acid-catalyzed paths. The selective oxidation of 3,4-dimethoxy acetophenone and 4-methyl acetophenone by performic acid into aromatic esters have been experimentally investigated. The kinetic rate constants were obtained in the temperature range of 303 to 323 K. The selectivity of product was also explained by the NBO electric charge analysis. The calculated activation energy barriers of the B-V reaction of DMOAP and MAP were in good agreement with those of experiment.
- Liu, Bo,Meng, Xiang-Guang,Li, Wei-Yi,Zhou, Liang-Chun,Hu, Chang-Wei
-
scheme or table
p. 2920 - 2926
(2012/05/20)
-
- New approach for the construction of the coumarin frame and application in the total synthesis of natural products
-
A new synthetic approach is described for building the coumarin scaffold through the Lewis acid-promoted cyclization of novel aryl 3-(dimethylamino)prop- 2-enoates 2a - 2f. The latter precursors were prepared via aminomethylenation of the corresponding aryl acetates 4a - 4f with the Bredereck reagent. This approach was used for the synthesis of biologically active natural compounds 1a - 1f, through a three-step procedure starting from the corresponding phenols.
- Jerezano, Alberto,Jimenez, Fabiola,Del Carmen Cruz, Maria,Montiel, Luisa E.,Delgado, Francisco,Tamariz, Joaquin
-
experimental part
p. 185 - 198
(2011/04/17)
-
- Gold(III)-catalyzed direct acetoxylation of arenes with iodobenzene diacetate
-
AuCl3-catalyzed direct acetoxylation of electron-rich aromatic compounds has been achieved with iodobenzene diacetate as the acetoxylation reagent.
- Qiu, Di,Zheng, Zhitong,Mo, Fanyang,Xiao, Qing,Tian, Yu,Zhang, Yan,Wang, Jianbo
-
supporting information; experimental part
p. 4988 - 4991
(2011/11/13)
-
- Synthesis and biological evaluation of coumarin-based inhibitors of NAD(P)H: Quinone oxidoreductase-1 (NQO1)
-
The synthesis is reported here of two novel series of inhibitors of human NAD(P)H quinone oxidoreductase-1 (NQO1), an enzyme overexpressed in several types of tumor cell. The first series comprises substituted symmetric dicoumarol analogues; the second series contains hybrid compounds where one 4-hydroxycoumarin systemis replaced by a different aromatic moiety. Several compounds show equivalent or improved NQO1 inhibition over dicoumarol, both in the presence and in the absence of added protein. Further, correlation is demonstrated between the ability of these agents to inhibit NQO1 and computed binding affinity. We have solved the crystal structure of NQO1 complexed to a hybrid compound and find good agreement with the in silico model. For both MIA PaCa-2 pancreatic tumor cells and HCT116 colon cancer cells, dicoumarol shows the greatest toxicity of all compounds. Thus, we provide a computational, synthetic, and biological platform to generate competitive NQO1 inhibitors with superior pharmacological properties to dicoumarol. This will allow a more definitive study of NQO1 activity in cells, in particular, its drug activating/detoxifying properties and ability to modulate oncoprotein stability. 2009 American Chemical Society.
- Nolan, Karen A.,Doncaster, Jeremy R.,Dunstan, Mark S.,Scott, Katherine A.,Frenkel, A. David,Siegel, David,Ross, David,Barnes, John,Levy, Colin,Leys, David,Whitehead, Roger C.,Stratford, Ian J.,Bryce, Richard A.
-
experimental part
p. 7142 - 7156
(2010/07/20)
-
- Intramolecular versus intermolecular oxidative couplings of ester tethered di-aryl ethers
-
The oxidative cyclization of 3,4-dimethoxyphenyl 3,4-dimethoxyphenylacetate, through intramolecular biphenyl bond formation, was successful and gave the target seven-membered lactone in good yield (85-86%). All other ester substrates gave biphenyl products or their further oxidized products via intermolecular coupling of their radical cation intermediate with the neutral substrate. It appears that matching of the oxidation potentials and nucleophilicity of the two phenyl rings, the positioning of the ring substituents and the ease of E to Z isomerization about the ester C-O bond are important factors contributing to these product outcomes. Crown Copyright
- Taylor, Stephen R.,Ung, Alison T.,Pyne, Stephen G.,Skelton, Brian W.,White, Allan H.
-
p. 11377 - 11385
(2008/03/13)
-
- Synthesis of methoxy-substituted phenols by peracid oxidation of the aromatic ring
-
A novel benign protocol for the preparation of hydroxy-methoxybenzene derivatives is disclosed. By utilizing this protocol, activated aromatic compounds such as l,3-dimethoxy-2-methyl-benzene and 1-(2,6-dimethoxyphenyl) ethanone are smoothly converted to the corresponding monohydroxylated compound. The reaction can be considered to be a normal aromatic electrophilic substitution reaction, and the regioselectivity for the reaction thus follows the similar rules as for electrophilic substitutions. The protocol is composed by benign reagents, namely, hydogenperoxide, acetic acid, and p-toluene sulfonic acid, which lead to the production of ethaneperoxoic acid in situ. The ethaneperoxoic acid operates as the hydroxylating reagent. The hydroxylation reaction is completed within a short period and requires moreover only mild experimental conditions, which make this novel protocol a green, cheap, and rapid process leading to hydroxy-methoxybenzene derivatives. The proposed reaction mechanism is supported by density functional theory and NMR spectroscopy experiments. The mechanism is constituted by two discrete steps: (a) addition of OH+ to the most nucleophilic carbon atom of the aromatic ring, which is the rate-determining step, and (b) the loss of the proton from the aromatic ring.
- Bjorsvik, Hans-Rene,Occhipinti, Giovanni,Gambarotti, Cristian,Cerasino, Leonardo,Jensen, Vidar R.
-
p. 7290 - 7296
(2007/10/03)
-
- The Baeyer-Villiger Oxidation of Aromatic Aldehydes and Ketones with Hydrogen Peroxide Catalyzed by Selenium Compounds
-
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.
- Syper, Ludwik
-
p. 167 - 172
(2007/10/02)
-
- An Unusual O-Methylation in the Allan-Robinson Synthesis of Purpurascenin, a 3,5,6,7,8,2',4',5'-Octamethoxyflavone
-
In the Allan-Robinson synthesis of 3,5,6,7,8,2',4',5'-octamethoxyflavone (Purpurascenin, I), from 2,4,6-trihydroxy-3,5,ω-trimethoxyacetophenone (IV) and asarylic anhydride, the expected intermediate, 5,7-dihydroxy-3,6,8,2',4',5'-hexamethoxyflavone (III) unusually gets further methylated to give 5-hydroxy-3,6,7,8,2',4',5'-heptamethoxyflavone (II) during the course of reaction.The possible mechanism of methylation is discussed.
- Patwardhan, Sarita A.,Gupta, Amrit S.
-
p. 3786 - 3795
(2007/10/02)
-
- Preparation of Regioselectively Protected Hydroquinones by Phosphorylation of p-Benzoquinones with Trialkyl Phosphites
-
The title reaction has been applied to 10 monosubstituted p-benzoquinones (Scheme 2, Table).The regioselectivity of the O-phosphorylation is influenced by bulky substituents (t-butyl and trimethylsilyl) and, electronically, by the methoxy group.The regioselectivity, which is high in nonpolar media (benzene), is lower in polar solvents (CH2Cl2 and CH3CN).The synthetic potential of this transformation, exemplified by the preparation of compounds 29 (Scheme 3) and 32 (Scheme 4), is considerably extended by applying milder methods for the phosphate hydrolysis and by using the reagent couple P(OCH3)3/trimethylsilyl chloride, which gives clean access to p-hydroxyphenyl phosphates. p-Benzoquinones 4h and 4i with strong ?-acceptor substituents react in a different way, giving phosphonates.The electronically induced regioselectivity of the O- and C-phosphorylation is in accordance with the preferences expected for the attack by a nucleophilic phosphorylation agent.
- Duthaler, Rudolf O.,Lyle, Paulette A.,Heuberger, Christoph
-
p. 1406 - 1426
(2007/10/02)
-