122-46-3Relevant academic research and scientific papers
STRUCTURE-REACTIVITY CORRELATION IN THE PYRIDINOLYSIS OF SUBSTITUTED PHENYL ACETATES
Yoh, Soo-Dong,Kang, Joong-Kyu,Kim, Sung-Hong
, p. 2167 - 2174 (1988)
The pyridinolysis of substituted phenyl acetates in acetonitrile was investigated with an electric conductivity method.The rates of these reactions were increased with electron-donating group in pyridine and electron-withdrawing group in phenyl acetate. ρX (X;substituents in phenyl ring) values increase gradually according to the electron-donating ability in pyridine substituents, but the /ρY/ (Y;substituents in pyridine ring) values decrease with that of substituents.The β values increase with increasing electron-withdrawing ability of the substituents in the phenyl ring, it can be inferred that N---C bond formation increases progressively p-methyl to p-nitrophenyl acetates.This is in agreement with prediction of substituent effects for a simple SN2 displacement reaction.The sensitivity parameters, β and ρ, are inter-related and are themselves sensitive to the reactivity of the system.All above results are interpreted in terms of a dissociative SN2 mechanism involving a metastable tetrahedral intermediate.
Steric effect of NHC ligands in Pd(II)–NHC-catalyzed non-directed C–H acetoxylation of simple arenes
Mandal, Tanmoy,Yadav, Sudha,Choudhury, Joyanta
, (2021)
Although there has been a lot of progress in oxidative arene C–H functionalization reactions catalyzed by Pd(II/IV) system, the non-directed, site-selective functionalization of arene molecules is still challenging. It has been established that ligands play a pivotal role in controlling rate- as well as selectivity-determining step in a catalytic cycle involving well-defined metal-ligand bonding. N-heterocyclic carbene (NHC) ligands have had a tremendous contribution in the recent extraordinary success of achieving high reactivity and excellent selectivity in many catalytic processes including cross-coupling and olefin-metathesis reactions. However, the immense potential of these NHC ligands in improving site-selectivity of non-directed catalytic C–H functionalization reactions of simple arenes is yet to be realized, where overriding the electronic bias on deciding selectivity is a burdensome task. The presented work demonstrated an initiative step in this regard. Herein, a series of well-defined discrete [Pd(NHCR′R)(py)I2] complexes with systematically varied degree of spatial congestion at the Pd centre, exerted through the R and R’ substituents on the NHC ligand, were explored in controlling the activity as well as the site-selectivity of non-directed acetoxylation of representative monosubstituted and disubstituted simple arenes (such as toluene, iodobenzene and bromobenzene, naphthalene and 1,2-dichlorobenzene). The resulting best yields were found to be 75% for toluene and 65% for bromobenzene with [Pd(NHCMePh)(py)I2], 75% for iodobenzene and 79% for naphthalene with [Pd(NHCMeMe)(py)I2], and 41% for 1,2-dichlorobenzene with [Pd(NHCCyCy)(py)I2]. Most importantly, with increasing the bulkiness of the NHC ligand in the complexes, the selectivity of the distal C-acetoxylated products in comparison to the proximal ones, was enhanced to a great extent in all cases. Considering the vast library of NHC ligands, this study underscores the future opportunity to develop more strategies to improve the activity and the crucial site-selectivity of C–H functionalization reactions in simple as well as complex organic molecules.
P2O5/SiO2 as an efficient reagent for esterification of phenols in dry media
Eshghi,Rafei,Karimi
, p. 771 - 774 (2001)
A simple and efficient method for esterification of carboxylic acid with phenols using P2O5/SiO2 reagent in dry media is reported.
Palladium-Catalyzed Desilylative Acyloxylation of Silicon-Carbon Bonds on (Trimethylsilyl)arenes: Synthesis of Phenol Derivatives from Trimethylsilylarenes
Gondo, Keisuke,Oyamada, Juzo,Kitamura, Tsugio
, p. 4778 - 4781 (2015)
A strategy for desilylative acetoxylation of (trimethylsilyl)arenes has been developed in which (trimethylsilyl)arenes are converted into acetoxyarenes. The direct acetoxylation is performed in the presence of 5 mol % of Pd(OAc)2 and PhI(OCOCF3)2 (1.5 equiv) in AcOH at 80°C for 17 h. The acetoxyarenes are obtained in good to high yields (67-98%). The synthetic utility is demonstrated with a one-pot transformation of (trimethylsilyl)arenes to phenols by successive acetoxylation and hydrolysis. Furthermore, desilylative acyloxylation of 2-(trimethylsilyl)naphthalene using several carboxylic acids has been conducted.
Nucleophilicity of Phenolates in the Reaction with p-Nitrophenyl Acetate in Ethanol
Guanti, Giuseppe,Cevasco, Giorgio,Thea, Sergio,Dell'Erba, Carlo,Petrillo, Giovanni
, p. 327 - 330 (1981)
The rate of release of p-nitrophenol in the reaction of nine substituted phenolates with p-nitrophenyl acetate has been determined by spectrophotometric measurements in absolute ethanol at 22 deg C.The phenolate anion is the reactive species and competes with ethoxide anion, arising from solvolysis of the phenolate, for nucleophilic attack on the ester carbonyl carbon atoms.From the observed reaction rates the solvolysis constants and the pKa values of the phenols were obtained.The second-order rate constants for phenoxide anions were correlated with the pKa values of the corresponding phenols giving a Broensted β value of 0.57.A comparison with the nucleophilic reactivity of arenethiolates towards the same substrate in ethanol has been made.The rate-determining step is probably the expulsion of the leaving group in the raection of arenethiolates, whereas it is the nucleophile attack in the reaction of phenoxides.
PtII and PdII complexes with a trans-chelating bis(pyridyl) ligand
Wang, Nan,McCormick, Theresa M.,Ko, Soo-Byung,Wang, Suning
, p. 4463 - 4469 (2012)
An atropisomeric bis(pyridyl) chelate ligand bis{3,3'-[N-Ph-2-(2'-py) indolyl]} (bpib) has been found to readily form trans-chelating PdII and PtII complexes. Two such complexes, Pt(bpib)Cl2 and Pd(bpib)Cl2 have
Liquid-phase reactions of isomeric methylphenols with ozone
Galstyan
, p. 15 - 19 (2010)
Ozonation of isomeric methylphenols in acetic anhydride was studied. Here, acetic anhydride acts simultaneously as solvent and acylating agent. In the presence of a mineral acid methylphenols were converted into methylphenyl acetates during preparation of solutions for ozonation. The major products in the oxidation of isomeric methylphenyl acetates with ozone were aliphatic peroxides (80-90%); oxidation of the methyl group gave rise to the corresponding acetoxybenzyl acetates (7-14%) and acetoxybenzylidene diacetates (3-6%). A probable scheme for the liquid-phase oxidation of methylphenyl acetates with ozone in acetic anhydride was proposed.
Palladium(II) acetate catalyzed aromatic substitution reaction
Stock, Leon M.,Tse, Kwok-Tuen,Vorvick, Linda J.,Walstrum, Steven A.
, p. 1757 - 1759 (1981)
Relative rate measurements indicate that the palladation reaction, although nonselective, adheres to the selectivity relationship for electrophilic aromatic substitution. Kinetic isotope effects and the dependence of the rate on oxidant concentration implicate arylpalladium(II) and arylpalladium(IV) compounds as intermediates in the reactions leading to biaryls and aryl acetates.
A PdII Carbene Complex with Anthracene Side-Arms for π-Stacking on Reduced Graphene Oxide (rGO): Activity towards Undirected C–H Oxygenation of Arenes
Majeed, Maitham H.,Shayesteh, Payam,Persson, Axel R.,Wallenberg, L. Reine,Schnadt, Joachim,Wendt, Ola F.
, p. 4742 - 4746 (2018)
An N-heterocyclic carbene palladium(II) complex containing two anthracene side arms was immobilized on the surface of reduced graphene oxide (rGO) by π-stacking. The activity of the homogeneous analogue and the supported complex in undirected C–H acetoxylation reaction of arenes was studied. The results show that the catalytic efficiency in acetoxylation of benzene is improved in the immobilized materials compared to the homogeneous analogue. According to XPS analysis, the immobilized catalyst maintains the original oxidation state of PdII after the catalytic reaction.
An efficient method to prepare aryl acetates by the carbonylation of aryl methyl ethers or phenols
Zhang, Dejin,Yang, Guoqiang,Xiong, Junping,Liu, Jia,Hu, Xingbang,Zhang, Zhibing
, p. 2683 - 2687 (2021/02/16)
Synthesis of valuable chemicals from lignin based compounds is critical for the application of biomass. Here, we develop a method of preparing aryl acetates by the carbonylation of aryl methyl ethers or phenols under low CO pressure. Good to excellent yields of aryl acetates were obtained using different substrates, and a possible reaction mechanism was proposed by conducting a series of control experiments. This method may provide a potential way for the utilization of lignin.
