- Preparation method of 2-bromo-4-fluoro-6-methylphenol
-
The invention discloses a preparation method of 2-bromo-4-fluoro-6-methylphenol, and belongs to the technical field of fine chemical engineering. The preparation method of 2-bromo-4-fluoro-6-methylphenol comprises the following steps of: (1) diazotization hydrolysis reaction: carrying out diazotization hydrolysis reaction on 2-methyl-4-fluoroaniline to obtain 2-methyl-4-fluorophenol; and (2) bromination reaction: carrying out bromination reaction on the 2-methyl-4-fluorophenol prepared in the step (1) to prepare the 2-bromo-4-fluoro-6-methylphenol. According to the method, nitrosyl sulfuric acid is adopted as an acylation reagent, waste acid obtained after diazotization hydrolysis is completed does not contain salt, acidic wastewater is easy to treat, and industrial production is facilitated; bromine used in the bromination reaction is greatly reduced, and the technological process is more environmentally friendly.
- -
-
Paragraph 0027-0029; 0032-0035
(2020/11/09)
-
- Preparation method of 2- bromo -4- fluoro -6- methyl phenol (by machine translation)
-
2 - (,) The process for preparing .2 -methylnitrobenzene, (:) by subjecting 1 fluorine - 2 2-methylnitrobenzene prepared in step (:) to a reduction reaction 4 - to prepare; fluorine - 2 2-methylphenol. 2. The method comprises the following steps :) of nitrosation reaction 1 (4 -) diazo hydrolysis. 4 - g - 2 2-methylphenol prepared by the following steps: The process of the present invention, is simple 3% by diazotization reaction: to prepare 3 the 2 fluorine - 2 2-methylphenol obtained in step (4 -) by means of a reduction reaction step (4 -) to form 4 - fluorine. 2 2 (4 2 -)-methylphenol prepared by the same step as a process. for the preparation of fine chemical products by 2 - means of the bromination reaction step of the preparation, method as shown in the following step (. a).]) The method comprises the following steps: (a)) diazo reaction : (by machine translation)
- -
-
Paragraph 0015; 0017; 0019
(2020/03/17)
-
- Catalytic activation of unstrained C(aryl)–C(aryl) bonds in 2,2′-biphenols
-
Transition metal catalysis has emerged as an important means for C–C activation that allows mild and selective transformations. However, the current scope of C–C bonds that can be activated is primarily restricted to either highly strained systems or more polarized C–C bonds. In contrast, the catalytic activation of non-polar and unstrained C–C moieties remains an unmet challenge. Here we report a general approach for the catalytic activation of the unstrained C(aryl)–C(aryl) bonds in 2,2′-biphenols. The key is to utilize the phenol moiety as a handle to install phosphinites as a recyclable directing group. Using hydrogen gas as the reductant, monophenols are obtained with a low catalyst loading and high functional group tolerance. This approach is also applied to the synthesis of 2,3,4-trisubstituted phenols. A further mechanistic study suggests that the C–C activation step is mediated by a rhodium(i) monohydride species. Finally, a preliminary study on breaking the inert biphenolic moieties in lignin models is illustrated.
- Zhu, Jun,Wang, Jianchun,Dong, Guangbin
-
-
- Metal-free oxidative fluorination of phenols with [18F]fluoride
-
The radiochemical synthesis of [18F]4-fluorophenols is based on phenol umpolung under oxidative conditions and direct nucleophilic fluorination with [18F]fluoride (see scheme, TBAF=tetra-n-butylammonium fluoride, TFA=trifluoroacetic acid). Readily available O-unprotected 4-tert-butyl phenols are used as precursors in this one-pot protocol. The reaction is completed in less than 30 minutes at room temperature and can be performed using standard or microfluidic technology. Copyright
- Gao, Zhanghua,Lim, Yee Hwee,Tredwell, Matthew,Li, Lei,Verhoog, Stefan,Hopkinson, Matthew,Kaluza, Wojciech,Collier, Thomas Lee,Passchier, Jan,Huiban, Mickael,Gouverneur, Véronique
-
supporting information; experimental part
p. 6733 - 6737
(2012/08/28)
-
- A novel improvement in ArLPdF catalytic fluorination of aromatic compounds
-
In this study, we used reverse micellar medium for overcoming the disadvantages of ArLMF catalytic fluorination of aromatic compounds. It not only enhanced the fluorination rate, but also widened the scope of reaction for bromoaromatics with electron donating and withdrawing functionalities at ortho position. Various bromoaromatic compounds were fluorinated using the biarylphosphine ligand i.e. cyclohexyl BrettPhos ligand, along with [cinnamylPdCl]2, and CsF as the fluoride source in reverse micellar media. The anisotropic palisade layer of reverse micelles provided the active site for reaction. The most crucial factor in the critical reductive elimination step could be the spatial orientation of ArLPdF complex in the palisade layer; forming ArF as the final product in high yield with excellent selectivity.
- Samant, Bhupesh S.,Bhagwat, Sunil S.
-
experimental part
p. 191 - 194
(2012/01/05)
-
- 2-(Trimethylsilyl)ethanol as a new alcohol equivalent for copper-catalyzed coupling of aryl iodides
-
2-(Trimethylsilyl)ethanol as a new alcohol equivalent has been employed for copper-catalyzed coupling of aryl iodides. Using mild reaction conditions, it has been observed that substituted phenols and phenols with sensitive functional groups can be readily prepared.
- Dibakar, Mullick,Prakash, Anjanappa,Selvakumar, Kumaravel,Ruckmani, Kandasamy,Sivakumar, Manickam
-
p. 5338 - 5341
(2011/10/19)
-
- An easy two-step reduction of salicylic acids and alcohols to 2-methylphenols
-
Salicylic acids and alcohols can be reduced to 2-methylphenols by a simple two steps procedure. Reaction conditions were optimized carrying out a study on the solvent effect and the amount of the reducing agent. The improved procedure resulted particularly useful in the synthesis of deuterated building blocks of biological interest. Georg Thieme Verlag Stuttgart.
- Mazzini, Francesco,Salvadori, Piero
-
p. 2479 - 2481
(2007/10/03)
-
- On the Mechanism of the Oxidation of Toluenes in Artificial P450 Model Systems: Formation of Benzyl Alcohols, Benzaldehydes and Phenols
-
Systems with pentafluoroiodosylbenzene (PFIB) and hemin (FeTPPCl8Cl) in dichloromethane were adopted to study the activities of the model system using toluenes as substrates for P450 enzymes. The oxidation products were mainly corresponding benzyl alcohols and benzaldehydes. Previously reported suspension systems were extended to homogeneous mixed solution systems of CH2Cl2/CH3OH/H2O to study the oxidation of benzyl alcohols to the corresponding benzaldehydes: the Hammett relation with ρ = -0.86 against ?+. As benzaldehydes were scarcely observed in natural P450 systems, the formation of benzaldehyde seemed characteristic only of the "open" model systems. In suspension systems, the product ratios between corresponding benzaldehydes and benzyl alcohols (ald/alc) were about 0.1-0.4, specific to the substituents and conditions applied. Curiously, the ratios (ald/alc) increased with the electronegativity of the substituents on the phenyl rings of the toluene derivatives. Time course experiments in suspension systems indicated that benzyl alcohols and benzaldehydes were formed not stepwise, but simultaneously from toluene. Separate experiments indicated that the reaction of benzyl alcohol to benzaldehyde was four-fold faster than that of toluene to benzyl alcohol. The rate was not enough to elucidate the amount of benzaldehyde. We suggest that the benzyl radical is formed by hydrogen abstraction and is attacked by the second oxidant, PFIB. Rebounding of the hydroxyl radical and the reaction with the oxidant were competitive depending on the conditions. Additionally, small amounts of phenols were formed from toluenes with electron-donating substituents. This was a minor reaction on which the aromatic hydroxylation occurred via epoxidation under the present conditions.
- Nakano, Taku,Kawabata, Sally,Sugihara, Tamami,Agatsuma, Noriko,Kakuda, Hiroko,Mori, Yoshihiro
-
p. 2353 - 2360
(2007/10/03)
-
- Preparation of aromatic fluorides: Facile photo-induced fluorinative decomposition of arenediazonium salts and their related compounds using pyridine-nHF
-
By employing pyridine-nHF solution, the photo-induced fluorinative decomposition of arenediazonium salts (ArN2BF4) (fluoro-dediazoniation) and the related compounds, such as quinonediazides and triazenes, has been successfully carried out to produce the corresponding aromatic fluorides (ArF) in good yields. The rate in the fluoro-dediazoniation of para-substituted ArN2BF4 in pyridine-nHF solution did not obey the classical Hammett equation but conformed well to Taft's treatment [dual substituent parameter relationships (DSP)]. In the thermal fluoro-dediazoniation of ArN2BF4 the rate of reaction was significantly influenced by the substituents in the substrates. On the contrary, only a slight effect by the substituents was observed on the rate of the photo-induced fluoro-dediazoniation of ArN2BF4.
- Sawaguchi, Masanori,Fukuhara, Tsuyoshi,Yoneda, Norihiko
-
p. 127 - 133
(2007/10/03)
-
- Facile preparation of aromatic fluorides by deaminative fluorination of aminoarenes using hydrogen fluoride combined with bases
-
One-pot deaminative fluorination of aminoarenes including heteroaromatics, namely, diazotization of aminoarenes followed by in situ fluoro-dediazoniation of the corresponding diazonium ions, was successfully accomplished to produce fluoroarenes in high yields by using hydrogen fluoride combined with base solutions. The diazotization stage has been found to play the most important part in yielding fluoroarenes effectively. It was greatly influenced by the composition of the HF solution and enhanced by employing appropriate amounts of bases such as pyridine under carefully controlled conditions. The fluoro-dediazoniation stage was effectively accelerated photochemically to afford fluoroarenes having polar substituents such as hydroxyl, nitro and so on in high yields.
- Yoneda,Fukuhara
-
-
- Facile Preparation of Aromatic Fluorides by the Fluoro-Dediazoniation of Aromatic Diazonium Tetrafluoroborates Using HF-Pyridine Solution
-
The fluoro-dediazoniation of ArN2BF4 using HF-pyridine solution has been successfully carried out either thermaly or photochemically to afford the corresponding ArF in good yields.Particularly, the photochemically induced reaction in HF-pyridine was a useful tool for the preparation of ArF having polar substituents such as halogens, OH, OMe, CF3, etc.
- Fukuhara, Tsuyoshi,Sekiguchi, Manabu,Yoneda, Norihiko
-
p. 1011 - 1012
(2007/10/02)
-
- The Preparation of p-Fluorophenols from p-Aminophenols: Diazotization and Fluorodiazoniation in Pyridine-HF.
-
A facile preparation of p-fluorophenols is described by the diazotization of p-aminophenols and fluorodediazoniation in situ using HF in a pyridine solution (pyridine-HF) under carefully controlled conditions.
- Fukuhara, Tsuyoshi,Yoneda, Norihiko,Takamura, Kouki,Suzuki, Akira
-
p. 299 - 304
(2007/10/02)
-
- DIRECT FLUORINATION OF PHENOL AND CRESOLS
-
A study has been made of the reaction of phenol with elemental fluorine using a variety of solvents and reaction temperatures.Yields of o- and p-fluorophenol were obtained as high as 85percent.The isomer ratio changed drastically between phenol conversions of 10percent and 56percent.The o-isomer changed to unidentified polymeric substances at higher conversion, but it might also be assumed that interconversion of some isomers is occuring.The three cresols have also been succesfully fluorinated with elemental fluorine. p-Cresol gave some expected 2-fluoroderivative but also formed a fluorocyclohexadienyl ketone.
- Misaki, Susumu
-
p. 159 - 172
(2007/10/02)
-