- Kinetics and process parameter studies in oxidative chlorination of 4-methylphenol under phase-transfer conditions
-
The effect of phase-transfer catalysts on the rate and selectivity of oxidative chlorination of 4-methylphenol was studied in ethylenedichloride with HCl-H2O2. Under identical reaction conditions, the rate of oxidative chlorination increased 6-7-fold in the presence of a phase-transfer catalyst (PTC) like tetraheptylammonium chloride in comparison to an ordinary two-phase system with no PTC. The activation energy was found to be 78 kJ/mol, and the reaction was found to be first-order on 4-methylphenol. An appropriate mechanism has been proposed.
- Mukhopadhyay, Sudip,Mukhopadhyaya, Jayanta K.,Ponde, Datta E.,Cohen, Shlomo,Kurkalli, Basan G. S.
-
-
Read Online
- Ceria-promoted Co@NC catalyst for biofuel upgrade: synergy between ceria and cobalt species
-
Ceria-promoted Co@NC (NC, N doped carbon) catalysts are prepared by pyrolysis of biomass materials. Characterization results indicate that ceria and Co species facilitate the distribution of each other due to the formation of a Ce-O-Co solid solution. The specific surface area of the catalyst increased from 378.77 to 537.7 m2g?1viathe introduction of ceria. The electron transfer from Co to Ce further enhanced their interaction, and Co species facilitate the formation of more defective oxygen vacancies on ceria, which are beneficial to the activities of catalytic hydrogenation and catalytic transfer hydrogenation (CTH), respectively. Thus, Co/Ce@NC (0.99% Co loading) pyrolyzed at 850 °C exhibits excellent performance in the hydrodeoxygenation (HDO) of vanillin with high metal utilization. Catalytic hydrogenation and CTH coexisted in the presence of H2and ethanol, and >99% yield of creosol can be obtained in each of them. The reaction processes are monitored. No intermediate is found in aqueous media, while ethoxymethyl-4-methoxy-2-phenol is detected in ethanol. Moreover, Co/Ce@NC presents outstanding stability and general applicability. This work provides new insights into the construction of M@NC (M, metal) catalysts and the HDO process of biofuel upgrade.
- Wang, Bowei,Gao, Ruixiao,Zhang, Dan,Zeng, Yuyao,Zhang, Fangying,Yan, Xilong,Li, Yang,Chen, Ligong
-
supporting information
p. 8541 - 8553
(2021/04/12)
-
- Nickel-catalyzed intelligent reductive transformation of the aldehyde group using hydrogen
-
The selective transformation of the aldehyde group (-CHO) in multifunctional oxygenates is a key challenge in the development of sustainable biomass feedstock. Herein, a smart Ni-MFC catalyst was developed from a 2D Ni-based metal-organic framework (MOF), which efficiently promoted the transformation of -CHO in the presence of H2 to a methyl group (-CH3) via the reductive etherification and hydrogenolysis of the C-O ether bond in methanol. Moreover, the catalytic process could be controlled to directionally produce methyl ether (-CH2OR) using the reductive etherification protocol. For the catalytic reduction of vanillin, the Ni-MFC-700 catalyst guaranteed the full conversion of vanillin and 96.5% yield of the desired 2-methoxy-4-methylphenol (MMP), while the Ni-MFC-500 catalyst afforded about 82.7% yield of 4-(methoxymethyl)-2-methoxyphenol in methanol solvent. This is a novel and promising approach for the valorization of multifunctional oxygenates and biomass-derived platform compounds.
- Tong, Xinli,Guo, Pengfei,Liao, Shengyun,Xue, Song,Zhang, Haigang
-
p. 5828 - 5840
(2019/11/11)
-
- Rate enhancements due to ultrasound in isoquinolinium dichromate and isoquinolinium chlorochromate catalyzed chlorination of aromatic compounds in presence of KHSO4/KCl
-
Chlorination of aromatic compounds underwent magnificent rate accelerations in isoquinolinium dichromate and isoquinolinium chlorochromate catalyzed chlorination of aromatic hydrocarbons in the presence of KCl and KHSO4. Reaction times reduced highly significantly from 4-5 h in conventional protocol to 30-40 min under sonication, followed by high yields of monochloro derivatives as products with high regioselectivity.
- Rajanna,Rao, A. Sambashiva,Chakravarthi,Reddy, K. Rajendar
-
p. 167 - 170
(2017/12/26)
-
- Kinetic and Mechanisms of the Homogeneous, Unimolecular Elimination of Phenyl Chloroformate and p-Tolyl Chloroformate in the Gas Phase
-
The gas-phase elimination of phenyl chloroformate gives chlorobenzene, 2-chlorophenol, CO2, and CO, whereasp-tolyl chloroformate produces p-chlorotoluene and 2-chloro-4-methylphenol CO2 and CO. The kinetic determination of phenyl chloroformate (440-480oC, 60-110 Torr) and p-tolyl chloroformate (430-480°C, 60-137 Torr) carried out in a deactivated static vessel, with the free radical inhibitor toluene always present, is homogeneous, unimolecular and follows a first-order rate law. The rate coefficient is expressed by the following Arrhenius equations: Phenyl chloroformate: Formation of chlorobenzene, log kI = (14.85 ± 0.38) - (260.4 ± 5.4) kJ mol-1 (2.303RT)-1; r = 0.9993 Formation of 2-chlorophenol, log kII = (12.76 ± 0.40) - (237.4 ± 5.6) kJ mol-1(2.303RT)-1; r = 0.9993 p-Tolyl chloroformate: Formation of p-chlorotoluene: log kI = (14.35 ± 0.28) - (252.0 ± 1.5) kJ mol-1 (2.303RT)-1; r = 0.9993 Formation of 2-chloro-4-methylphenol, log kII = (12.81 ± 0.16) - (222.2 ± 0.9) kJ mol-1(2.303RT)-1; r = 0.9995 The estimation of the kI values, which is the decarboxylation process in both substrates, suggests a mechanism involving an intramolecular nucleophilic displacement of the chlorine atom through a semipolar, concerted four-membered cyclic transition state structure; whereas the kII values, the decarbonylation in both substrates, imply an unusual migration of the chlorine atom to the aromatic ring through a semipolar, concerted five-membered cyclic transition state type of mechanism. The bond polarization of the C-Cl, in the sense Cδ+Clδ-, appears to be the rate-determining step of these elimination reactions.
- Lezama, Jesus,Chuchani, Gabriel
-
p. 664 - 670
(2015/09/07)
-
- Synthesis of deuterated benzopyran derivatives as selective COX-2 inhibitors with improved pharmacokinetic properties
-
We designed a series of specifically deuterated benzopyran analogues as new COX-2 inhibitors with the aim of improving their pharmacokinetic properties. As expected, the deuterated compounds retained potency and selectivity for COX-2. The new molecules possess improved pharmacokinetic profiles in rats compared to their nondeuterated congeners. Most importantly, the new compounds showed pharmacodynamic efficacy in several murine models of inflammation and pain. The benzopyran derivatives were separated into their enantiomers, and the activity was found to reside with the S-isomers. To streamline the synthesis of the desired S-isomers, an organocatalytic asymmetric domino oxa-Michael/aldol condensation reaction was developed for their preparation.
- Zhang, Yanmei,Tortorella, Micky D.,Wang, Yican,Liu, Jianqi,Tu, Zhengchao,Liu, Xiaorong,Bai, Yang,Wen, Dingsheng,Lu, Xin,Lu, Yongzhi,Talley, John J.
-
p. 1162 - 1166
(2014/12/10)
-
- Multisubstituted benzo[b]furans through a copper- and/or palladium-catalyzed assembly and functionalization process
-
Full details as well as the study of the scope, limitations, and further elaboration of a straightforward approach to the synthesis of 2,5,7-trisubstituted benzo[b]furans from 2-bromo- and 2-chloro-6-iodo-4- substituted phenols through a consecutive copper- and/or palladium-catalyzed assembly and functionalization process is described. Functionalization at the C(7) position is carried out by Suzuki-Miyaura cross-coupling, alkynylation, alkenylation, and C-N bond forming reactions. A one-pot protocol for the synthesis of 2,5,7-trisubstituted benzo[b]furans is also reported.
- Arcadi, Antonio,Blesi, Federico,Cacchi, Sandro,Fabrizi, Giancarlo,Goggiamani, Antonella,Marinelli, Fabio
-
p. 1857 - 1871
(2013/04/10)
-
- Cu-Mn spinel oxide catalyzed regioselective halogenation of phenols and N-heteroarenes
-
A novel simple, mild chemo- and regioselective method has been developed for the halogenation of phenols using Cu-Mn spinel oxide as a catalyst and N-halosuccinimide as halogenating agent. In the presence of Cu-Mn spinel oxide B, both electron-withdrawing and electron-donating groups bearing phenols gave monohalogenated products in good to excellent yields with highest para-selectivity. The para-substituted phenol gave monohalogenated product with good yield and ortho-selectivity. N-Heteroarenes such as indoles and imidazoles also gave monohalogenated products with high selectivity. Unlike the copper-catalyzed halogenation, the present method works well with electron-withdrawing group bearing phenols and gives comparatively better yields and selectivity. The Cu-Mn spinel catalyst is robust and reused three times under optimized conditions without any loss in catalytic activity. Nonphenolics did not undergo this transformation.
- Singh, Parvinder Pal,Thatikonda, Thanusha,Kumar, K. A. Aravinda,Sawant, Sanghapal D.,Singh, Baldev,Sharma, Amit Kumar,Sharma,Singh, Deepika,Vishwakarma, Ram A.
-
experimental part
p. 5823 - 5828
(2012/09/05)
-
- 2,5,7-Trisubstituted benzo[b]furans through a copper- and/or palladium-catalyzed assembly and functionalization process
-
A straightforward approach to the synthesis of 2,5,7-trisubstituted benzo[b]furans from 2-bromo- and 2-chloro-6-iodo-4-substituted phenols through a consecutive copper- and/or palladium-catalyzed assembly and functionalization process is described. Functionalization at the C(7) position is carried out by Suzuki-Miyaura cross-coupling and C-N bond forming reactions.
- Arcadi, Antonio,Blesi, Federico,Cacchi, Sandro,Fabrizi, Giancarlo,Goggiamani, Antonella
-
scheme or table
p. 5149 - 5152
(2011/10/12)
-
- Facile p-toluenesulfonic acid-promoted para-selective monobromination and chlorination of phenol and analogues
-
para-Regioselective bromination of phenol and analogues, promoted by p-toluenesulfonic acid, is achieved in high to excellent yields at room temperature with N-bromosuccinimide. Chlorination with N-chlorosuccinimide and catalysed by p-toluenesulfonic acid also gives para-chlorinated phenol analogues in good yields at room temperature. para-Bromination of phenol, promoted by p-toluenesulfonic acid, is achieved in excellent yields at room temperature with N-bromosuccinimide. p-Toluenesulfonic acid is also effective as a promoter of para-chlorination with N-chlorosuccinimide.
- Bovonsombat, Pakorn,Ali, Rameez,Khan, Chiraphorn,Leykajarakul, Juthamard,Pla-On, Kawin,Aphimanchindakul, Suraj,Pungcharoenpong, Natchapon,Timsuea, Nisit,Arunrat, Anchalee,Punpongjareorn, Napat
-
experimental part
p. 6928 - 6935
(2010/10/01)
-
- Kinetics of chlorination of phenol and monosubstituted phenols by t-butyl hypochlorite in aqueous alkaline medium
-
The kinetics of chlorination of the parent and sixteen monosubstituted phenols (2-chloro, 2-methyl, 2-carboxy, 2-nitro, 3-chloro, 3-methyl, 3-carboxy, 4-fluoro, 4-chloro, 4-bromo, 4-methyl, 4-ethyl, 4-methoxy, 4-carboxy, 4-acetyl and 4-nitro) by t-BuOCl have been studied in aqueous alkaline medium. The rates of reactions show first order kinetics each in |t-BuOCl| and |XC 6H4OH| and inverse first order in |OH-|. Variation in either ionic strength or addition of reaction product has no significant effect on the rates of reactions, while lowering of the dielectric constant of the medium increases the rate. The rates are measured at different temperatures and the activation parameters for all the phenols computed. A mechanism involving the electrophilic attack of phenoxide ions by HOCl in the rate determining step is suggested. The rates decrease in the order: 3-CH 3 > 2-CH3 > 4-OCH3 > 4-CH3 > 4-C2H5 > H > 3-Cl > 3-COO- > 4-F > 2-COO- > 4-Br > 2-Cl > 4-Cl > 4-COO- > 4-COCH3 > 2-NO2 > 4-NO2. Hammett equation of the type, log k = -3.44 - 2.35 ρ is found to be valid for substituent effects. The enthalpy and entropy of activation are correlated.
- Moodithaya,Gowda, B. Thimme
-
p. 420 - 425
(2007/10/03)
-
- Indium-mediated chemoselective deprotection of trichloroethoxycarbonyl and trichloroacetyl groups
-
A new, mild, and chemoselective method for the deprotection of trichloroethoxylcarbonyl and trichloroacetyl groups is described.
- Valluri, Muralikrishna,Mineno, Tomoko,Hindupur, Rama M.,Avery, Mitchell A.
-
p. 7153 - 7154
(2007/10/03)
-
- Kinetics and mechanism of chlorination of phenol and substituted phenols by sodium hypochlorite in aqueous alkaline medium
-
The kinetics of chlorination of the parent and thirteen substituted phenols (2-methyl, 2-chloro, 2-carboxy, 3-methyl, 3-chloro, 3-carboxy, 4-methyl, 4-ethyl, 4-chloro, 4-bromo, 4-carboxy, 4-acetyl and 4-nitro phenols) by NaOCl have been studied in aqueous alkaline medium under varying conditions. The rates show first order kinetics each in [NaOCl] and [(X)C6H4(OH)] and inverse first order in [OH-]. Variation in ionic strength of the medium and addition of Cl have no significant effect on the rates of reactions. The rates of the reactions are measured at different temperatures and the activation parameters for all the phenols computed. A mechanism involving the electrophilic attack of the phenoxide ions by NaOCl in the rate determining step has been considered. The values of the pre-equilibrium and the rate determining steps have been calculated for all the phenols. The rates decrease in the order: 3-CH3 >2-CH3 >4-C2H5 = 4-CH3 >phenol >3-COO = 3-Cl > 2-COO >4-COO >2-Cl ? 4-Cl ? 4-Br > 4-COCH3 >4-NO2. Hammett plot of the type, log kobs = -2.88 -3.2980σ is found to be valid. The correlation between the enthalpies and the free energies of activations is reasonably linear with an isokinetic temperature of 300 K. Further, the energies of activation of all the phenols are optimised corresponding to the log A of the parent phenol through the equation, Ea = 2.303 RT (log A - log kobs). Similarly log A values of all the phenols are optimised corresponding to the Ea of PhOH through the equation, log A = log kobs + Ea/2.303RT. Ea increases with the introduction of electron-withdrawing groups into the benzene ring, while the introduction of the electron-releasing groups lowers Ea for the reaction. Similarly log A decreases with the substitution of electron-withdrawing groups, while log A increases on substitution with the electron-releasing groups.
- Gowda,Mary
-
p. 1196 - 1202
(2007/10/03)
-
- Highly selective oxidative monochlorination to synthesize organic intermediates: 2-Chlorotoluene, 2-chloroaniline, 2-chlorophenol, and 2-chloro-4-methylphenol
-
An alternative manufacturing process scheme was developed to synthesize monochloro-substituted aromatic compounds in high selectivity, involving oxidalive chlorination by using HCI-H2O2. Thus, 2-chlorotoluene, 2-chloroaniline, and 2-chlorophenol were synthesized by oxidative chlorination followed by desulphonation or decarboxylation. Oxidative chlorination of 4-methylbenzenesulphonic acid, 4-methylbenzoic acid, 4-aminobenzoic acid, and 4-hydroxybenzoic acid by using a suitable ratio of reactantr:HCI:H2O2, and their subsequent desulphonation or decarboxylation, gave 60-85% yield of the desired products. Oxidative chlorination of 4-methylphenol by using HCI-H2O2 gave as high as 98% selectivity to the desired 2-chloro-4-methylphenol.
- Mukhopadhyay, Sudip,Chandnani, Kavita H.,Chandalia, Sampatraj B.
-
p. 196 - 200
(2013/09/08)
-
- Process for the preparation of 2-chloro-4-methylphenol
-
2-Chloro-4-methylphenol is prepared by reacting 4-methylphenol with a chlorinating agent in the presence of a catalyst system of one or more Lewis acids in a total amount of 0.1-10% by weight and one or more diaryl sulphides in a total amount of 0.1-10% by weight, all based on the amount of 4-methylphenol. The reaction temperature is 0°-100° C. The chlorinating agent is used in an amount of 0.5-1.5 mol per mole of 4-methylphenol. The reaction can be carried out until virtually complete consumption of the 4-methylphenol, high isomeric selectivity and high stage selectivity being observed.
- -
-
-
- Reactions of OH and SO4.- with Some Halobenzenes and Halotoluenes: A Radiation Chemical Study
-
The optical absorption and kinetic characteristics of the transients formed in the reactions of OH and SO4.- with bromobenzene, ortho and meta-isomers of chloro- and bromobenzenes, and monobromotoluenes have been studied by pulse radiolysis technique.The rates for OH reaction are generally higher (k = (1.7-4.4)X109 M-1s-1) than those found for the SO4.- reaction (k = (0.4-2.3)x109 M-1s-1). ρ+ values of -0.4 for OH and -1.2 for SO4.- reactions were obtained from the Hammett analysis.The formation of substituted hydroxycyclohexadienyl radicals (λmax = 315-330 nm) is the major reaction channel, and the phenoxyl type radical (λ >/=400 nm) formation is an additional minor process in the SO4.- reaction.Abstraction of H by SO4.- from the -CH3 group is only significant with the para-isomers of bromo- and chlorotoluenes.This result is in accord with the observed yields (70 percent of SO4.-) of the products resulting from the oxidation of the 4-chlorobenzyl radical in the presence of K3Fe(CN)6 under steady-state conditions.The total yields of the phenolic products accounting for >90 percent of OH and SO4.- suggest that the attack at the ipso positions is considerably small.The rate constants for OH reactions relative to benzene at positions 3 and 6 of 2-chlorotoluene and positions 2 and 3 of 4-chlorotoluene are between 1.18 and 1.39, indicating that the directing effects of -CH3 and -Cl groups are comparable.This is also reflected in the additive effects of activation of the ortho and para-positions and deactivation of meta-positions by these substituents in 3-chlorotoluene.
- Merga, Getahun,Rao, B. S. M.,Mohan, H.,Mittal, J. P.
-
p. 9158 - 9164
(2007/10/02)
-
- Highly Selective Aromatic Chlorinations. Part 2. The Chlorination of Substituted Phenols, Anisoles, Anilines, and Related Compounds with N-Chloroamines in Acidic Solution
-
Phenols, anisoles, anilines, and related compounds are chlorinated in trifluoroacetic acid at room temperature by N-chlorodialkylamines and N-chlorotrialkylammonium salts.With monsubstituted compounds and their 2- and 3-substituted derivatives the reaction occurs efficiently and selectively at the 4-position.The reactivity of these substrates and the selectivity of their chlorinations are determined by electronic rather than steric effects of the substituent.Blocking the reaction with a substituent at the 4-position generally leads to only poor or moderate yields of the 2-chlorinated product.Evidence for radical and cation radical intermediates has been obtained in the reactions of some of the 4-substituted reactants and the mechanism of chlorination is discussed in the light of these findings.The reactions of selected substrates have been scaled up to give laboratory syntheses.
- Smith, John R. Lindsay,McKeer, Linda C.,Taylor, Jonathan M.
-
p. 385 - 392
(2007/10/02)
-
- ipso NITRATION. XXIX. NITRATION OF SUBSTITUTED 4-METHYLANISOLES AND PHENOLS
-
Nitration of 2-chloro-4-methylanisole (1a) in acetic anhydride gives (Z)-4-chloro-3-methoxy-6-methyl-6-nitrocyclohexa-2,4-dienyl acetate (2a), 2-chloro-4-methyl-4-nitrocyclohexa-2,5-dienone (3a), and 2-chloro-4-methyl-6-nitroanisole (4a).Similarly 2-bromo-4-methylanisole (1b) gives (Z)-4-bromo-3-methoxy-6-methyl-6-nitrocyclohexa-2,4-dienyl acetate (2b), 2-bromo-4-methyl-4-nitrocyclohexa-2,5-dienone (3b), and 2-bromo-4-methyl-6-nitroanisole (4b), whereas 4-methyl-2-nitro-anisole (1c) gives (Z)-3-methoxy-6-methyl-4,6-dinitrocyclohexa-2,4-dienyl acetate (2c), (Z)-3-methoxy-6-methyl-2,6-dinitrocyclohexa-2,4-dienyl acetate (7), and 4-methyl-2,6-dinitroanisole (4c).Nitration of 3-chloro-4-methylanisole (9a) gives 3-chloro-4-methyl-4-nitrocyclohexa-2,5-dienone (10a), 3-chloro-4-methyl-2-nitro anisole (11a), and 5-chloro-4-methyl-2-nitroanisole (12a), and 4-methyl-3-nitroanisole (9c) gives (Z)-3-methoxy-6-methyl-5,6-dinitrocyclohexa-2,4-dienyl acetate (13), 4-methyl-2,3-dinitroanisole (11c), and 4-methyl-2,5-dinitroanisole (12c).Nitration of 2-chloro-4-methylphenol (14) in chloroform gives 3a and 2-chloro-4-methyl-6-nitrophenol (5a), and 3-chloro-4-methylphenol (15) gives dienone 10a, 3-chloro-4-methyl-2-nitrophenol (16), and 5-chloro-4-methyl-2-nitrophenol (17).
- Fischer, Alfred,Henderson, George N.,RayMahasay, Sumit
-
p. 1233 - 1240
(2007/10/02)
-
- Preparation of p-hydroxybenzaldehyde derivatives
-
A 4-hydroxybenzaldehyde derivative of the formula: STR1 wherein each of R1, R2, R3 and R4 is selected from the group consisting of hydrogen atom, halogen atoms, lower alkyl groups or lower alkoxy groups, which is useful as intermediate for the production of medicines or agricultural chemicals, or as flavor, is produced by the reaction of a p-cresol derivative of the formula: STR2 wherein each of R1, R2, R3 and R4 is as defined above, with oxygen or oxygen-containing gas in the presence of a base and a catalytic amount of cobalt compound or metallic cobalt.
- -
-
-
- Electrophilic Aromatic Substitution. Part 28. The Mechanism of Nitration of Some 4-Substituted Anisoles and Phenols, and of Rearrangement of the Intermediate 4-Nitro-4-substituted-cyclohexa-2,5-dienones
-
The kinetics of nitration in sulphuric acid of 2-chloro-4-methyl-, 4-chloro-, 2,4-dichloro-, and 4-fluoroanisole and of the corresponding phenols have been determined.The reaction products from the anisoles and from 2-chloro-4-methyl- and 4-fluoro-phenol have been determined.Results for 4-methylanisole supplementary to earlier ones are also reported.Generally the anisoles give the 2-nitro-derivatives and the 2-nitrophenols, and from 2-chloro-4-methylanisole, 2-chloro-4-methyl-4-nitrocyclohexa-2,5-dienone was formed as an intermediate.The decomposition of this dienone in sulphuric acid, like those of others, changes from a non-acid-catalysed to an acid-catalysed form with increasing acidity.The first form is regarded as a decomposition into an aryloxyl radical and nitrogen dioxide which can recombine to give the 2-nitrophenol.The formation of a small amount of 2-(4-fluorophenoxy)-4-fluorophenol in the nitration of 4-fluorophenol is seen as support for this view.The acid-catalysed form is regarded as the decomposition of the protonated dienone into a phenol-nitronium ion encounter-pair which can give the nitrophenol.A consequence of the mechanism is that if the phenol were nitrated at less than the encounter rate, the phenol itself would in appropriate conditions be a product of the ipso-nitration of the original anisole. 4-Methyl-, 2-chloro-4-methyl-, and 4-chloro-phenol have been so identified.Quantitative analysis of the results allows evaluation of the partitioning of dienone decomposition between the two modes.The mechanism accounts for the formation from 2,4-dichloro-anisole of both 2,4-dichloro-6- and 2,4-dichloro-5-nitroanisole, but only 2,4-dichloro-6-nitrophenol.
- Bloomfield, Colin,Manglik, Ajay K.,Moodie, Roy B.,Schofield, Kenneth,Tobin, Geoffrey D.
-
-
- PhSeCl AS A CHLORINATING AGENT FOR ACTIVATED BENZENE DERIVATIVES
-
Regiospecific chlorination of some aromatic compounds using benzeneselenyl chloride are reported.
- Ayorinde, Folahan O.
-
p. 2077 - 2078
(2007/10/02)
-
- Electrophilic Chlorination of 4-Methylphenols with Molecular Chlorine. Synthesis of Dimethoxy Aromatics by Methanolysis of 4-Chloro-4-methylcyclcohexa-2,5-dienones
-
The chlorination of p-cresol (1a), 2,4-dimethylphenol (1b), 3,4-dimethylphenol (1c), 2,4,5-trimethylphenol (1d), 2,4,6-trimethylphenol (1e) and the various possible mono- and dichloro derivatives of these phenols (3a-d, 6a and 6 c) with molecular chlorine was investigated in dichloromethane or dimethyl formamide solution.The 2,6-substituted p-cresol derivatives all give quantitative yields of 4-chloro-4-methylcyclohexa-2,5-dienones (5b, 5d, 7a, 7c and 2e), whereas the less substituted p-cresol derivatives give a 20-25percent yield of corresponding 4-chloro-4-methylcyclohexa-2,5-dienones (2a-d, 5a and 5c), the other products being chlorinated phenols.Treatment of 4-chloro-4-methylcyclohexa-2,5-dienones with at least one of the double bonds of the ring unsubstituted (2a-c and 4a) with methanol gave a quantitative yield of a 1,3-dimethoxybenzene derivative (9a-c and 10), whereas similar treatment of 4-chloro-2,4,5-trimethylcyclohexa-2,5-dienone (2d) gave 5-methoxy-2,3-dimethylbenzyl methyl ether (11).Treatment of the other 4-chlorodienones with methanol gave the corresponding 4-methoxydienones.Electrophilic chlorination of certain p-cresol derivatives followed by methanolysis hence is a facile although low-yield method for 3-methoxylation or selective side chain oxidation of these p-cresol derivatives.
- Bergquist, Karl-Erik,Nilsson, Anders,Ronlan, Alvin
-
p. 675 - 684
(2007/10/02)
-