1004-66-6Relevant articles and documents
Molecular Orbital Calculations and 13C NMR Studies To Explain a Regiospecific Demethylation of 3-Alkyl-1,2-dimethoxybenzenes
Jardon, Phillip W.,Vickery, Euin H.,Pahler, Leon F.,Pourahmady, Naser,Mains, Gilbert J.,Eisenbraun, Edmund J.
, p. 2130 - 2135 (1984)
This study was performed to explain a regiospecific demethylation of 3-alkyl-1,2-dimethoxybenzenes.PRDDO-MO calculations show that the low-energy conformation of the carbon of a methoxy group having two ortho neighbors on a benzene ring is located out of the plane of the aromatic ring, whereas a methoxy group with only one ortho neighbor executes restricted rotation in the plane of the ring.The carbon portion of the methoxy group is turned away from the neighboring substituent.These calculations also show that the atomic charge on the oxygen atom in the former caseexceeds that in the latter.The carbon of a methoxy group with two ortho neighbors yields 13C NMR T1 relaxation times longer than those with only one ortho neighbor, also suggesting that the methoxy group with two ortho neighbors is crowded out of the plane of the aromatic ring. 13C NMR chemical shifts of these ortho-substituted methoxybenzenes did not correlate well with shifts predicted from published additive parameters; this again suggests an unusual methoxy group orientation and distribution of electrons.The forced rotation of a methoxy group out of the plane of the benzene ring diminishes the release of electrons from the methoxy group to the benzene ring.The resulting higher atomic charge on the oxygen and the orientation of the oxygen orbitals facilitate complexation with Lewis acids and methoxy group cleavage.
Methylation of Alcohols, Phenols, and Carboxylic Acids, and Selective Monomethylation of Diols and Dicarboxylic Acids with Dimethyl Sulfate by Use of Alumina
Ogawa, Haruo,Ichimura, Youko,Chihara, Teiji,Teratani, Shousuke,Taya, Kazuo
, p. 2481 - 2484 (1986)
Alcohols in cyclohexane give their methyl ethers in high yields by the use of a combination of dimethyl sulfate and alumina.Some diols and dicarboxylic acids adsorbed on alumina react with dimethyl sulfate and produce the corresponding monomethyl ethers and esters in high selectivities.
Selective catalytic conversion of guaiacol to phenols over a molybdenum carbide catalyst
Ma, Rui,Cui, Kai,Yang, Le,Ma, Xiaolei,Li, Yongdan
, p. 10299 - 10301 (2015)
An activated carbon supported α-molybdenum carbide catalyst (α-MoC1-x/AC) showed remarkable activity in the selective deoxygenation of guaiacol to substituted mono-phenols in low carbon number alcohol solvents. Combined selectivities of up to 85% for phenol and alkylphenols were obtained at 340°C for α-MoC1-x/AC at 87% conversion in supercritical ethanol. The reaction occurs via consecutive demethylation followed by a dehydroxylation route instead of a direct demethoxygenation pathway.
AGGREGATION OF LITHIUM PHENOLATES IN WEAKLY POLAR APROTIC SOLVENTS.
Jackman,DeBrosse
, p. 4177 - 4184 (1983)
The aggregation of lithium phenolate, 3,5-dimethylphenolate, 2,6-dimethylphenolate, and 2,6-di-tert-butylphenolate in dioxalane, dimethoxyethane, and pyridine has been investigated by a variety of methods including studies of vapor pressure barometry, **1**3C chemical shifts, **7Li nuclear quadrupole coupling constants, and **1**3C spin-lattice relaxation times. The phenolates with no ortho substituents from tetramers under most conditions. In pyridine at low concentrations and temperature the tetramers coexist with dimers. Lithium 2,6-dimethylphenolate forms dimers under all conditions studied, and lithium 2,6-di-tert-butylphenolate exists as a monomer or an oligomer depending on conditions. Attempts to establish solvation numbers for the aggregates from solvent **1**3C relaxation times have not been successful, and the reason for the failure, very fast solvent exchange, is discussed. The kinetics and thermodynamics of exchange between dimers and tetramers of lithium 3,5-dimentylphenolate in pyridine have been investigated, and the mechanism of interconversion is shown to involve additional solvation of the tetramer prior to dissociation.
Methylation of phenol and its derivatives with dimethyl carbonate in the presence of Mn2(CO)10, W(CO)6, and Co2(CO)8
Khusnutdinov,Shchadneva,Mayakova, Yu. Yu.
, p. 330 - 334 (2015)
Aryl methyl ethers were synthesized by reactions of phenol, substituted phenols, and α- and β-naphthols with dimethyl carbonate in the presence of manganese, tungsten, and cobalt carbonyls. Optimal reactant and catalyst ratios and reaction conditions were found to ensure selective formation of aryl methyl ethers.
Pd-Catalyzed ipso, meta-Dimethylation of ortho-Substituted Iodoarenes via a Base-Controlled C-H Activation Cascade with Dimethyl Carbonate as the Methyl Source
Wu, Zhuo,Wei, Feng,Wan, Bin,Zhang, Yanghui
supporting information, p. 4524 - 4530 (2021/05/04)
A methyl group can have a profound impact on the pharmacological properties of organic molecules. Hence, developing methylation methods and methylating reagents is essential in medicinal chemistry. We report a palladium-catalyzed dimethylation reaction of ortho-substituted iodoarenes using dimethyl carbonate as a methyl source. In the presence of K2CO3 as a base, iodoarenes are dimethylated at the ipso- and meta-positions of the iodo group, which represents a novel strategy for meta-C-H methylation. With KOAc as the base, subsequent oxidative C(sp3)-H/C(sp3)-H coupling occurs; in this case, the overall transformation achieves triple C-H activation to form three new C-C bonds. These reactions allow expedient access to 2,6-dimethylated phenols, 2,3-dihydrobenzofurans, and indanes, which are ubiquitous structural motifs and essential synthetic intermediates of biologically and pharmacologically active compounds.
Trialkylammonium salt degradation: Implications for methylation and cross-coupling
Assante, Michele,Baillie, Sharon E.,Juba, Vanessa,Leach, Andrew G.,McKinney, David,Reid, Marc,Washington, Jack B.,Yan, Chunhui
, p. 6949 - 6963 (2021/06/02)
Trialkylammonium (most notably N,N,N-trimethylanilinium) salts are known to display dual reactivity through both the aryl group and the N-methyl groups. These salts have thus been widely applied in cross-coupling, aryl etherification, fluorine radiolabelling, phase-transfer catalysis, supramolecular recognition, polymer design, and (more recently) methylation. However, their application as electrophilic methylating reagents remains somewhat underexplored, and an understanding of their arylation versus methylation reactivities is lacking. This study presents a mechanistic degradation analysis of N,N,N-trimethylanilinium salts and highlights the implications for synthetic applications of this important class of salts. Kinetic degradation studies, in both solid and solution phases, have delivered insights into the physical and chemical parameters affecting anilinium salt stability. 1H NMR kinetic analysis of salt degradation has evidenced thermal degradation to methyl iodide and the parent aniline, consistent with a closed-shell SN2-centred degradative pathway, and methyl iodide being the key reactive species in applied methylation procedures. Furthermore, the effect of halide and non-nucleophilic counterions on salt degradation has been investigated, along with deuterium isotope and solvent effects. New mechanistic insights have enabled the investigation of the use of trimethylanilinium salts in O-methylation and in improved cross-coupling strategies. Finally, detailed computational studies have helped highlight limitations in the current state-of-the-art of solvation modelling of reaction in which the bulk medium undergoes experimentally observable changes over the reaction timecourse. This journal is
Selective O-methylation of phenols and benzyl alcohols in simple pyridinium based ionic liquids
Das, Pranab Jyoti,Das, Jupitara
, p. 94 - 98 (2015/06/08)
Synthesis of pyridinium based ionic liquids were reported and applied as catalyst for the selective O-methylation of phenols and benzyl alcohols. The reactions were carried out by using dimethylcarbonate (DMC) as the methylating agent. High selectivity, high yield and recyclability of the ionic liquids are important features of the reactions.
Microwave mediated protection of hindered phenols and alcohols
Pothi, Tejas,Dawange, Mahesh,Chavan, Kamlesh,Sharma, Rajiv,Deka, Nabajyoti
, p. 706 - 711 (2013/03/28)
Hindered phenols and alcohols were protected as their corresponding ethers using different alkylating agents in presence of KOH/DMSO under microwave irradiation.
Development of bis(2-picolyl)amine-zinc chelates for imidazole receptors
Routasalo, Taina,Helaja, Juho,Kavakka, Jari,Koskinen, Ari M. P.
experimental part, p. 3190 - 3199 (2009/04/07)
New phenyl and phenol bis(2-picolyl)amine (Dpa) derivatives have been synthesized in order to generate zinc chelates for imidazole anion receptors. Previously, binuclear phenolic zinc and copper chelates have shown affinity for pyrophosphate and guanidine anions, respectively. Herein we report significant imidazole affinity increasing from 2.38 × 106 to 2.90 × 107 for phenol-bridged binuclear zinc-Dpa chelates, as evidenced by dynamic and titration 1H NMR studies. Among the Dpa chelates investigated, the zinc-coordinated phenol group plays a crucial role in the mechanism of anion binding. Low-temperature 1H NMR experiments suggest a σν-symmetric geometry for the imidazole chelate. Computational DFT studies at the B3LYP level of theory imply that imidazole binding displaces the phenol bridge between the zinc ions. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
