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Chain-Breaking Phenolic 2,3-Dihydrobenzo[b]selenophene Antioxidants: Proximity Effects and Regeneration Studies
Phenolic 2,3-dihydrobenzo[b]selenophene antioxidants bearing an OH-group ortho (9), meta (10, 11) and para (8) to the Se were prepared by seleno-Claisen rearrangement/intramolecular hydroselenation. meta-Isomer (11) was studied by X-ray crystallography. The radical-trapping activity and regenerability of compounds 8–11 were evaluated using a two-phase system in which linoleic acid was undergoing peroxidation in the lipid phase while regeneration of the antioxidant by co-antioxidants (N-acetylcysteine, glutathione, dithiothreitol, ascorbic acid, tris(carboxyethyl)phosphine hydrochloride) was ongoing in the aqueous layer. Compound 9 quenched peroxyl radicals more efficiently than α-tocopherol. It also provided the most long-lasting antioxidant protection. With thiol co-antioxidants it could inhibit peroxidation for more than five-fold longer than the natural product. Regeneration was more efficient when the aqueous phase pH was slightly acidic. Since calculated O?H bond dissociation energies for 8–11 were substantially larger than for α-tocopherol, an antioxidant mechanism involving O-atom transfer from peroxyl to selenium was proposed. The resulting phenolic selenoxide/alkoxyl radical would then exchange a hydrogen atom in a solvent cage before antioxidant regeneration at the aqueous lipid interphase.
Singh, Vijay P.,Yan, Jiajie,Poon, Jia-Fei,Gates, Paul J.,Butcher, Ray J.,Engman, Lars
p. 15080 - 15088
(2017)
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Catalytic SNAr Hydroxylation and Alkoxylation of Aryl Fluorides
Nucleophilic aromatic substitution (SNAr) is a powerful strategy for incorporating a heteroatom into an aromatic ring by displacement of a leaving group with a nucleophile, but this method is limited to electron-deficient arenes. We have now established a reliable method for accessing phenols and phenyl alkyl ethers via catalytic SNAr reactions. The method is applicable to a broad array of electron-rich and neutral aryl fluorides, which are inert under classical SNAr conditions. Although the mechanism of SNAr reactions involving metal arene complexes is hypothesized to involve a stepwise pathway (addition followed by elimination), experimental data that support this hypothesis is still under exploration. Mechanistic studies and DFT calculations suggest either a stepwise or stepwise-like energy profile. Notably, we isolated a rhodium η5-cyclohexadienyl complex intermediate with an sp3-hybridized carbon bearing both a nucleophile and a leaving group.
Kang, Qi-Kai,Li, Ke,Li, Yuntong,Lin, Yunzhi,Shi, Hang,Xu, Lun
supporting information
p. 20391 - 20399
(2021/08/13)

Direct bromodeboronation of arylboronic acids with CuBr2 in water
An efficient and practical method has been developed for the preparation of aryl bromides via the direct bromodeboronation of arylboronic acids with CuBr2 in water. This strategy provides several advantages, such as being ligand-free, base-free, high yielding, and functional group tolerant.
Tang, Yan-Ling,Xia, Xian-Song,Gao, Jin-Chun,Li, Min-Xin,Mao, Ze-Wei
(2021/01/05)

Chiral secondary phosphine oxide pre-ligand and application thereof
The invention discloses a chiral secondary phosphine oxide pre-ligand and application thereof. The structure of the ligand is as shown in Formula I, where R. 1 . R2 , R3 And R4 Hydrogen, benzyl, substituted alkyl, substituted or unsubstituted aryl. The more preferred structural formula comprises 4 structural general formulas shown in the general formula I in the following formula: I-d, and the formula is shown in the general formula. Based on the designed asymmetric catalytic reaction system, the stability and the easy preparation of the comprehensive test ligand under the hydrocarbon activation condition are synthesized, and finally the chiral secondary oxidation phosphorus precursor with the double functional groups in the oxidation and heating environment is selected. The catalyst formed by the front ligand and the active metal compound has high activity and high selectivity in the reaction of constructing a chiral center, and has the stability.
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Paragraph 0033-0036

(2021/10/20)

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations
While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive-free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.
Deckers, Kristina,Fricke, Christoph,Schoenebeck, Franziska
supporting information
p. 18717 - 18722
(2020/08/25)

Dehydroxyalkylative halogenation of C(aryl)-C bonds of aryl alcohols
We herein report Cu mediated side-directed dehydroxyalkylative halogenation of aryl alcohols. C(aryl)-C bonds of aryl alcohols were effectively cleaved, affording the corresponding aryl chlorides, bromides and iodides in excellent yields. Aryl alcohols could serve as both aromatic electrophilic and radical synthetic equivalents during the reaction.
Liu, Mingyang,Zhang, Zhanrong,Liu, Huizhen,Wu, Tianbin,Han, Buxing
supporting information
p. 7120 - 7123
(2020/07/14)

Mild and Regioselective Bromination of Phenols with TMSBr
In this work, an unexpected promoting effect of by-product thioether was observed, leading to a mild and regioselective bromination of phenols with TMSBr. This method can tolerate a series of functional groups such as the reactive methoxyl, amide, fluoro, chloro, bromo, aldehyde, ketone and ester groups, and has the potential to recycle the by-product thioether and isolate the desired product under column chromatography-free conditions. Mechanism studies revealed that O–H···S hydrogen bond may be formed between phenol and by-product thioether. Possibly owing to the steric hindrance effect from by-product thioether, the electrophilic bromination at para-position of phenols is much favorable.
Ma, Xiantao,Yu, Jing,Jiang, Mengyuan,Wang, Mengyu,Tang, Lin,Wei, Mengmeng,Zhou, Qiuju
supporting information
p. 4593 - 4596
(2019/07/05)

Application of biosynthesized palladium nanoparticles (Pd NPs) on Rosa canina fruit extract-modified graphene oxide as heterogeneous nanocatalyst for cyanation of aryl halides
A green palladium (Pd)-based catalyst supported on Rosa canina fruit extract-modified graphene oxide [Pd nanoparticles (NPs)/reduced graphene oxide (RGO)-Rosa canina] hybrid materials has been used as a recoverable and heterogeneous nanocatalyst for cyanating aryl halides using K4[Fe (CN)6] as the resource of cyanide. The nitriles were achieved in good to high yield, and the catalyst can be recovered and reused for up to seven cycles with no remarkable decrease in its catalytic activity.
Hemmati, Saba,Sedrpoushan, Alireza,Soudalizadeh, Nazanin,Khosravi, Kaveh,Hekmati, Malak
(2019/08/12)

Iridium-Catalyzed C(sp3)?H Addition of Methyl Ethers across Intramolecular Carbon–Carbon Double Bonds Giving 2,3-Dihydrobenzofurans
Intramolecular addition of an O-methyl C(sp3)?H bond across a carbon-carbon double bond occurs in the iridium-catalyzed reaction of methyl 2-(propen-2-yl)phenyl ethers. The Ir/(S)-DTBM-SEGPHOS catalyst promotes the reaction efficiently in toluene at 110–135 °C to afford 3,3-dimethyl-2,3-dihydrobenzofurans. Enantioselective C(sp3)?H addition is achieved in the reaction of methyl 2-(1-siloxyethenyl)phenyl ethers, affording enantioenriched 3-hydroxy-2,3-dihydrobenzofuran derivatives with up to 96% ee. (Figure presented.).
Ohmura, Toshimichi,Kusaka, Satoshi,Torigoe, Takeru,Suginome, Michinori
supporting information
p. 4448 - 4453
(2019/09/16)

Method for catalyzing deaminized boric acid esterification or halogenation of arylamine
The invention belongs to the technical field of organic synthesis and in particular discloses a method for catalyzing deaminized boric acid esterification or halogenation of arylamine. The method comprises the following steps: putting arylamine and a nitroso type compound into a mixed solvent, and performing a reaction at 0-5 DEG; and further adding a raw material capable of providing a functionalization group A and a catalysis amount of a reaction accelerator, and performing deamination functionalization reaction under light radiation at 10-50 DEG C, so as to obtain a product that an amino site of the arylamine is modified by the functionalization group A. Due to synergetic control on substrates, reaction solvents, material mixing modes, temperatures, reaction accelerators and addition amounts, boric acid esterification or halogenation of arylamine, particularly electron donating substituted arylamine which is hard to treat effectively in technical schemes of the industry, can be achieved.
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Paragraph 0063; 0091-0093; 0120-0121

(2020/01/12)

Transition-metal-free decarboxylative bromination of aromatic carboxylic acids
Methods for the conversion of aliphatic acids to alkyl halides have progressed significantly over the past century, however, the analogous decarboxylative bromination of aromatic acids has remained a longstanding challenge. The development of efficient methods for the synthesis of aryl bromides is of great importance as they are versatile reagents in synthesis and are present in many functional molecules. Herein we report a transition metal-free decarboxylative bromination of aromatic acids. The reaction is applicable to many electron-rich aromatic and heteroaromatic acids which have previously proved poor substrates for Hunsdiecker-type reactions. In addition, our preliminary mechanistic study suggests that radical intermediates are not involved in this reaction, which is in contrast to classical Hunsdiecker-type reactivity. Overall, the process demonstrates a useful method for producing valuable reagents from inexpensive and abundant starting materials.
Quibell, Jacob M.,Perry, Gregory J. P.,Cannas, Diego M.,Larrosa, Igor
p. 3860 - 3865
(2018/04/26)

From Anilines to Aryl Ethers: A Facile, Efficient, and Versatile Synthetic Method Employing Mild Conditions
We have developed a simple and direct method for the synthesis of aryl ethers by reacting alcohols/phenols (ROH) with aryl ammonium salts (ArNMe3+), which are readily prepared from anilines (ArNR′2, R′=H or Me). This reaction proceeds smoothly and rapidly (within a few hours) at room temperature in the presence of a commercially available base, such as KOtBu or KHMDS, and has a broad substrate scope with respect to both ROH and ArNR′2. It is scalable and compatible with a wide range of functional groups.
Wang, Dong-Yu,Yang, Ze-Kun,Wang, Chao,Zhang, Ao,Uchiyama, Masanobu
supporting information
p. 3641 - 3645
(2018/03/13)

Zwitterionic-Salt-Catalyzed Site-Selective Monobromination of Arenes
A zwitterionic-salt-catalyzed electrophilic monobromination of arenes with high regioselectivity has been developed. Under mild reaction conditions, a wide range of monobrominated aromatic compounds can be obtained in excellent yields. The reaction can be operated using an extremely low catalyst loading (0.05 mol %) with the inexpensive brominating agent N-bromosuccinimide. The versatility of this catalytic protocol has been demonstrated by the scale-up reaction with a 0.01 mol % catalyst loading to provide the selectively halogenated compound in quantitative yield.
Xiong, Xiaodong,Tan, Fei,Yeung, Ying-Yeung
p. 4243 - 4246
(2017/08/23)

A highly efficient heterogeneous copper-catalyzed chlorodeboronation of arylboronic acids leading to chlorinated arenes
A highly efficient heterogeneous copper-catalyzed chlorodeboronation of arylboronic acids with inexpensive N-chlorosuccinimide (NCS) was achieved in MeCN in the presence of 10 mol% of l-proline-functionalized MCM-41-immobilized copper(i) complex [MCM-41-l-proline-CuCl] under mild conditions, yielding a variety of aryl chlorides in excellent yields. This method proved to be tolerant of a broad range of functional groups and particularly useful for the conversion of electron-deficient arylboronic acids to aryl chlorides, a transformation that is inefficient without copper catalysis. This heterogeneous copper catalyst can be recovered by a simple filtration of the reaction solution and recycled for at least 10 times without any decreases in activity.
He, Wen,Zhang, Rongli,Cai, Mingzhong
p. 764 - 770
(2017/01/13)

Sono-bromination of aromatic compounds based on the ultrasonic advanced oxidation processes
A novel, mild "sono-halogenation" of various aromatic compounds with potassium halide was investigated under ultrasound in a biphasic carbon tetrachloride/water medium. The feasibility study was first undertaken with the potassium bromide and then extended to chloride and iodide analogues. This methodology could be considered as a new expansion of the ultrasonic advanced oxidation processes (UAOPs) into a synthetic aspect as the developed methodology is linked to the sonolytic disappearance of carbon tetrachloride. Advantages of the present method are not only that the manipulation of the bromination is simple and green, but also that the halogenating agents used are readily available, inexpensive, and easy-handling.
Fujita, Mitsue,Lévêque, Jean-Marc,Komatsu, Naoki,Kimura, Takahide
p. 247 - 251
(2015/06/08)

Metal-free protodeboronation of electron-rich arene boronic acids and its application to ortho -functionalization of electron-rich arenes using a boronic acid as a blocking group
The metal-free thermal protodeboronation of various electron-rich arene boronic acids was studied. Several reaction parameters controlling this protodeboronation, such as solvent, temperature, and a proton source, have been investigated. On the basis of these studies, suitable reaction conditions for protodeboronation of several types of electron-rich arene boronic acids were provided. On the basis of this protodeboronation, a new protocol for the synthesis of ortho-functionalized electron-rich arenes from these boronic acids was developed using the boronic acid moiety as a blocking group in the electrophilic aromatic substitution reaction, followed by the removal of the boronic acid moiety via thermal protodeboronation. Mechanistic studies suggested that this protodeboronation might proceed via the complex formation of a boronic acid with a proton source, followed by the carbon-boron bond fission through σ-bond metathesis, to afford the corresponding arene compound and boric acid.
Ahn, Su-Jin,Lee, Chun-Young,Kim, Nak-Kyoon,Cheon, Cheol-Hong
p. 7277 - 7285
(2014/11/27)

Total synthesis and biological activity of marine alkaloid eudistomins Y1-Y7 and their analogues
Eudistomin Y class compounds are a series of β-carbolines which was originally isolated from a marine turnicate or ascidian near the South Korea Sea. These compounds contain bromo-substituted groups, which is one of the typical characters of marine natural products. We report herein the chemical synthesis and biological evaluation of seven new β-carboline-based metabolites, Eudistomins Y1-Y7, and their hydroxyl-methylated phenyl derivatives. Using bromo-substituted tryptamines and bromo-substituted phenylglyoxals as the key intermediates, Eudistomins Y 1-Y7 and their derivatives were synthesized via the acid-catalyzed Pictet-Spengler reaction and fully characterized by 1H- and 13C-NMR and mass spectroscopy. Biological studies revealed that all of the compounds showed moderate growth inhibitory activity against breast carcinoma cell line MDA-231 with IC50 of 15-63 μM and the inhibitory activities of hydroxyl-methylated phenyl products were higher than that of the corresponding natural products Eudistomins Y 1-Y7.
Jin, Huijuan,Zhang, Puyong,Bijian, Krikor,Ren, Sumei,Wan, Shengbiao,Alaoui-Jamali, Moulay A.,Jiang, Tao
p. 1427 - 1439
(2013/07/11)

Halogen exchange via a halogenation of diaryliodonium salts with cuprous halide
An efficient halogenation reaction has been developed with diaryliodonium salts and cuprous halides. Various diaryliodonium salts 1 could perform the reaction with readily available CuBr or CuCl in CH3CN at 80°C, assembling bromoarenes or chloroarenes in up to 92% yields. This provides us a method for the transformation from iodoarenes to other haloarenes.
Li, Jian,Liu, Li,Ding, Dong,Sun, Jiang-Tao
p. 541 - 548
(2014/01/06)

Electron transfer between hydrogen-bonded pyridylphenols and a photoexcited rhenium(I) complex
Two pyridylphenols with intramolecular hydrogen bonds between the phenol and pyridine units have been synthesized, characterized crystallographically, and investigated by cyclic voltammetry and UV/Vis spectroscopy. Reductive quenching of the triplet metal-to-ligand charge-transfer excited state of the [Re(CO)3(phen)(py)]+ complex (phen=1,10-phenanthroline, py=pyridine) by the two pyridylphenols and two reference phenol molecules is investigated by steady-state and time-resolved luminescence spectroscopy, as well as by transient absorption spectroscopy. Stern-Volmer analysis of the luminescence quenching data provides rate constants for the bimolecular excited-state quenching reactions. H/D kinetic isotope effects for the pyridylphenols are on the order of 2.0, and the bimolecular quenching reactions are up to 100 times faster with the pyridylphenols than with the reference phenols. This observation is attributed to the markedly less positive oxidation potentials of the pyridylphenols with respect to the reference phenols (≈0.5 V), which in turn is caused by proton coupling of the phenol oxidation process. Transient absorption spectroscopy provides unambiguous evidence for the photogeneration of phenoxyl radicals, that is, the overall photoreaction is clearly a proton-coupled electron-transfer process. A concerted effort: Two pyridylphenols with intramolecular hydrogen bonds react with a metal complex through concerted proton transfer (PT)-electron transfer (ET). Upon photoexcitation of the complex, ET occurs from the phenol to the metal, and the phenolic proton is transferred to the pyridine moiety (see picture; MLCT=metal-to-ligand charge transfer). Copyright
Herzog, William,Bronner, Catherine,Loeffler, Susanne,He, Bice,Kratzert, Daniel,Stalke, Dietmar,Hauser, Andreas,Wenger, Oliver S.
p. 1168 - 1176
(2013/06/27)

Amino acid intercalated layered double hydroxide catalyzed chemoselective methylation of phenols and thiophenols with dimethyl carbonate
Sixteen different amino acids are intercalated into Mg-Al layered double hydroxides (LDHs) by the reconstruction method and are characterized by powder XRD and FT-IR. The intercalated amino acid-LDHs (AA-LDHs) are used as catalysts for chemoselective O-methylation of phenol and S-methylation of thiophenol with dimethyl carbonate (DMC) as a green methylating agent. The intercalation behavior of various amino acids is influenced by various structural features of amino acids, namely, carbon chain length, structure, and physicochemical properties. In particular, amino acids possessing a hydrophobic side-chain show higher catalytic activity. A suitable reaction mechanism is proposed. The catalyst can also be recycled.
Subramanian, Thirumeni,Dhakshinamoorthy, Amarajothi,Pitchumani, Kasi
p. 7167 - 7170
(2013/12/04)

Halogenation and DNA cleavage via thermally stable arenediazonium camphorsulfonate salts
A series of stable arenediazonium camphorsulfonate salts (2a-2j) were synthesized by simple diazotization of several aromatic amines in the presence of sodium nitrite and camphorsulfonic acid. All the new arenediazonium camphorsulfonates, which were characterized by multinuclear (1H and 13C) NMR, IR, DSC, and X-ray diffraction analysis (2e and 2f) provide unambiguous proof for the molecular structures of 2e and 2f. The efficient application of these salts in halogenation reactions was studied in solvent and solvent-free conditions and the DNA cleavage activity was also assessed. These arenediazonium camphorsulfonate salts are noticed as efficient DNA cleaving agents.
Vajpayee, Vaishali,Moon, Mi Eun,Lee, Sunmi,Ravikumar, Sambandam,Kim, Hyunuk,Ahn, Byungchan,Choi, Seoyoon,Hong, Soon Ho,Chi, Ki-Whan
p. 3511 - 3517
(2013/04/23)

Aromatic substitution in ball mills: Formation of aryl chlorides and bromides using potassium peroxomonosulfate and NaX
Aryl chlorides and bromides are formed from arenes in a ball mill using KHSO5 and NaX (X = Cl, Br) as oxidant and halogen source, respectively. Investigation of the reaction parameters identified operating frequency, milling time, and the number of milling balls as the main influencing variables, as these determine the amount of energy provided to the reaction system. Assessment of liquid-assisted grinding conditions revealed, that the addition of solvents has no advantageous effect in this special case. Preferably activated arenes are halogenated, whereby bromination afforded higher product yields than chlorination. Most often reactions are regio- and chemoselective, since p-substitution was preferred and concurring side-chain oxidation of alkylated arenes by KHSO5 was not observed. The Royal Society of Chemistry.
Schmidt, Robert,Stolle, Achim,Ondruschka, Bernd
p. 1673 - 1679
(2013/02/22)

In situ acidic carbon dioxide/water system for selective oxybromination of electron-rich aromatics catalyzed by copper bromide
Carbon dioxide, being one of the major greenhouse gases responsible for global warming, its atmospheric level grows ever faster since the beginning of industrial era. Great efforts have been devoted to developing versatile technologies/processes to adjust and manipulate the rapid growth of CO 2 emission. Besides CO2 capture and storage/sequestration (CCS) to control its emission, chemical utilization of the captured CO 2 (CCU) emerges to be a rational technique for economical benefits as well as environmental concerns. As for the aim of CO2 utilization, an environmentally benign CO2/water reversible acidic system was developed for the copper (II)-catalyzed selective oxybromination of electron-rich aromatics without the need of any conventional acid additive and organic solvent. Notably, up to 95% yields of the bromination products were attained with good regio-selectivity when cupric bromide was used as the catalyst and lithium bromide as a cheap and easy handling bromine source under supercritical CO2. The catalytic system worked well for electron-rich aromatics including ethers, sulfides and mesitylene. Carbonic acid in situ formed from CO2 and water is supposed to act as the proton donator in the Bronsted acid-promoted reaction. Notably, CO2 in this study serves as a reaction medium and a promoter in conjunction with water and also provides safe environment for aerobic reactions. Given with excellent reaction efficiency as well as no need of neutralization disposal, this process thus represents an environmentally friendly approach for aerobic bromination of aromatics with essential reduction of CO2 emission as well as an economically beneficial way for application of captured CO2.
Liu, An-Hua,Ma, Ran,Zhang, Meng,He, Liang-Nian
p. 38 - 43
(2013/01/15)

Copper-catalyzed halogenation of arylboronic acids
In this Letter, a copper-catalyzed halogenation of arylboronic acids was described. This reaction tolerates a variety of functional groups, providing aromatic halides with good yields. It represents a facile and mild procedure to aryl halides.
Zhang, Guangyou,Lv, Guanglei,Li, Liping,Chen, Fan,Cheng, Jiang
experimental part
p. 1993 - 1995
(2011/04/25)

Efficient and economic halogenation of aryl amines via arenediazonium tosylate salts
Arenediazonium tosylate salts have been successfully employed as a new and efficient reagent in halogenation reactions. A novel and economic protocol has been developed for the bromination and chlorination of various anilines using arenediazonium tosylate salts. A wide variety of reaction conditions were studied in acetonitrile at either room temperature or 60 °C in the presence or absence of catalyst with good to excellent yields. A surprising result showed the formation of acetanilides as a major product of aniline and methyl-substituted aniline halogenations in high yields.
Lee, Young Min,Moon, Mi Eun,Vajpayee, Vaishali,Filimonov, Victor D.,Chi, Ki-Whan
experimental part
p. 7418 - 7422
(2010/10/01)

An expeditious and environmentally benign preparation of aryl halides from aryl amines by solvent-free grinding
An efficient solvent-free methodology for conversion of various aryl amines into bromides and chlorides via arenediazonium tosylate salts under grinding conditions is disclosed. This new methodology not only avoids the use of strong acids and expensive reagents for diazotization-halogenation reactions, but also decreases the amount of organic waste from the reaction process.
Moon, Mi Eun,Choi, Younghwa,Lee, Young Min,Vajpayee, Vaishali,Trusova, Marina,Filimonov, Victor D.,Chi, Ki-Whan
scheme or table
p. 6769 - 6771
(2011/03/17)

Relative basicities of ortho-, meta-, and para-substituted aryllithiums
(Chemical Equation Presented) The relative basicities of aryllithiums bearing methoxy, chlorine, fluorine, trifluoromethyl and trifluoromethoxy substituents at the ortho, meta, and para positions have been assessed. To this end, two aryllithiums of compar
Gorecka-Kobylinska, Joanna,Schlosser, Manfred
experimental part
p. 222 - 229
(2009/04/11)

Stereoselective bromination reactions using tridecylmethylphosphonium tribromide in a "stacked" reactor
(Chemical Equation Presented) A new reagent, tridecylmethylphosphonium tribromide, and new procedures for bromination reactions of unsaturated substrates (including one that allows several substrates to be reacted in sequence) are described. The procedures exploit the diffusion of components and the densities and immiscibilities of layers, including a fluorous "spacer" layer, within a reaction vessel. The stereoselectivities achieved in the reactions are superior in some cases to those found with other brominating reagents.
Ma, Kefeng,Li, Shaw,Weiss, Richard G.
supporting information; experimental part
p. 4155 - 4158
(2009/06/06)

Solvent-free Williamson synthesis: An efficient, simple, and convenient method for chemoselective etherification of phenols and bisphenols
Etherification of phenols with dimethyl- and diethylsulfates and benzyl chloride was performed efficiently in the presence of a suitable solid base, NaHCO3 or K2CO3, under solvent-free conditions. The reaction proceeded rapidly at low temperature, and the corresponding ethers were obtained with high purity and excellent yield. Selective etherification of electron-poor phenols in the presence of electron-rich ones and also selective mono-etherification of bisphenols are the noteworthy advantages of this method. This method is environmentally friendly. Copyright Taylor & Francis Group, LLC.
Massah, Ahmad R.,Mosharafian, Masumeh,Momeni, Ahamad R.,Aliyan, Hamid,Naghash, H. Javaherian,Adibnejad, Mohamad
p. 1807 - 1815
(2008/02/02)

Microwave-assisted methylation of carboxylic acids and phenolic compounds with dimethyl-carbonate under solvent-free condition
Phenolic compounds and carboxylic acids are methylated with dimethyl carbonate in the presence of a catalytic amount of BF3· OEt2, DBU, or KOH, in good to excellent yields under microwave irradiation and solvent-free conditions.
Rajabi, Fatemeh,Saidi, Mohammad R.
p. 4179 - 4188
(2007/10/03)

Facile Synthesis of 2-Bromo-3-fluorobenzonitrile: An Application and Study of the Halodeboronation of Aryl Boronic Acids
A scaleable synthesis of 2-bromo-3-fluorobenzonitrile via the NaOMe-catalyzed bromodeboronation of 2-cyano-6-fluorophenylboronic acid was developed. The generality of this transformation was demonstrated through the halodeboronation of a series of aryl boronic acids. Both aryl bromides and aryl chlorides were formed in good to excellent yields when the corresponding aryl boronic acid was treated with 1,3-dihalo-5,5-dimethylhydantoin and 5 mol % NaOMe.
Szumigala Jr., Ronald H.,Devine, Paul N.,Gauthier Jr., Donald R.,Volante
p. 566 - 569
(2007/10/03)

Effect of cyclodextrins on electrophilic aromatic bromination in aqueous solution
Cyclodextrins act as molecular reactors to change the ratios of the products of reactions of anisole, acetanilide, 3-methylanisole, and 3-methylacetanilide with pyridinium dichlorobromate. With anisole and acetanilide, bromination at the para position is favoured over ortho substitution, and the effect is greatest with α-cyclodextrin. In the reactions of the methylanisole and methylacetanilide, the cyclodextrins afford higher yields of monobrominated products and less of the di- and tribromides, and β-cyclodextrin has the greatest effect. These outcomes can be attributed to inclusion of the substrates within the cyclodextrins restricting access of the reagent adjacent to the methoxy and acetamido groups. The yields of 4-bromoanisole, 4-bromoacetanilide, 4-bromo-3-methylanisole, and 4-bromo-3-methylacetanilide are thus increased from 73 to 94, 55 to 98, 37 to 86, and 39 to 72%, respectively. Perhaps more significantly, the quantities of the corresponding by-products are substantially reduced, from 27 to 6, 45 to 2, 63 to 14, and 61 to 28%. Since the reactions occur readily in water at ambient temperature, the cyclodextrins make them very efficient.
Dumanski, Paul G.,Easton, Christopher J.,Lincoln, Stephen F.,Simpson, Jamie S.
p. 1107 - 1111
(2007/10/03)

Oxidative halogenation of aromatic compounds with metal halides and sodium bismuthate
A new mild and efficient method for aromatic halogenation with a wide variety of halides in the presence of sodium bismuthate NaBO3 in AcOH is reported. Metal halides of groups Ia, IIa, IIIa, IVa, Va, and the first row of transition elements are suitable for this method.
Muathen, Hussni A.
p. 164 - 168
(2007/10/03)

A new protocol for O-methylation of phenolic compounds with trimethyl phosphite or trimethyl phosphate under solvent-free condition and microwave irradiation
A simple method for the preparation of industrially important alkyl aryl ethers is reported. Several phenolic compounds such as phenols, naphthols, and hydroxy coumarins were O-methylated with trimethyl phosphite or trimethyl phosphate under microwave irradiation and solvent-free condition in almost quantitative yields. Reaction of 2-naphthol with trimethyl phosphate gave mixture of 2-methoxynaphthalene and 1-methyl-2-methoxynaphthalene while the reaction with trimethyl phosphite gave mostly 2-methoxynaphthalene. This method is highly efficient for the methylating of phenolic compounds with very easy experimental procedure and environmental friendly conditions.
Saidi, Mohammad R.,Rajabi, Fatemeh
p. 2343 - 2348
(2007/10/03)

An efficient and regioselective oxybromination of aromatic compounds using potassium bromide and oxone
A simple, efficient and regioselective method for oxybromination of aromatics is reported. The electrophilic substitution of bromine generated in situ from potassium bromide using oxone as an oxidant for the first time.
Narender,Srinivasu,Ramakrishna Prasad,Kulkarni,Raghavan
p. 2313 - 2318
(2007/10/03)

Pyridinium dichlorobromate: A new stable brominating agent for aromatic compounds
Pyridinium dichlorobromate (PyHBrCl2, 1) is a new example of iminium-trihalide complexes. The compound is prepared from pyridine and chlorine in the presence of aqueous hydrogen bromide. The crystalline trihalide is quite stable and acts as a safe source of positive bromine. It shows a remarkable reactivity towards aromatic compounds compared with other bromine complexes. It is also considered as a potential source for bromine chloride BrCl.
Muathen, Hussni A.
p. 169 - 171
(2007/10/03)

Transition metal complex, process for producing the same, olefin polymerization catalyst containing the transition metal complex and process for producing olefin polymers
The present invention relates to a transition metal complex, a process for producing the same, a polymerization catalsyt containing the transition metal complex and a process for producing polymers which uses the catalysts.
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(2008/06/13)

Halodediazoniations of dry arenediazonium o-benzenedisulfonimides in the presence or absence of an electron transfer catalyst. Easy general procedures to prepare aryl chlorides, bromides, and iodides
The paper reports the results of a wide study aimed at preparing aryl chlorides 3 (19 examples), bromides 4 (19 examples), and iodides 5 (9 examples) by halodediazoniation of dry arenediazonium o-benzenedisulfonimides 1 with tetraalkylammonium halides 2. The reactions were carried out in anhydrous acetonitrile at room temperature (~20 °C) in the presence of copper powder and at 60 °C or room temperature without the catalyst. In optimal conditions the yields were from good to excellent (60 reactions, 61- 94% yield), with only a few exceptions (8 reactions, 51-55% yield). A good amount of the o-benzenedisulfonimide (7) was always recovered from the reactions and could then be reused to prepare salts 1. An interesting aspect of this research is the surprising role of the anion of o- benzenedisulfonimide (9) as an electron transfer agent.
Barbero,Degani,Dughera,Fochi
p. 3448 - 3453
(2007/10/03)

Generation of interhalogen fluorides under mild conditions: A comparison of sluggish and reactive interhalogen fluorides
Interhalogen fluorides (XF; X = I, Br, or Cl) generated from xenon difluoride (XeF2) or triethylamine trihydrofluoride (TREAT HF) with iodine (I2), N-halosuccinimides (NXS; X = I, Br, or Cl), or alkylhypohalites (ROX; R = CH3 or t-Bu, X = Br or Cl) with alkenes and aromatics are reported. A comparison of the above reactions with other methods reported in the literature to generate interhalogen fluorides is made. Interhalogens generated from direct action of elemental fluorine (F2) or XF3 (X = I, Br, or Cl) with chlorine (Cl2), bromine (Br2), or iodine (I2) give a species that can react with electron-deficient alkenes or aromatics. These reagents are too reactive for electron-rich substrates. Interhalogen fluorides from reagents like NXS or ROX with XeF2 or amine HF are much less reactive and give good yields with electron-rich akenes or aromatics.
Shellhamer, Dale F.,Horney, Mark J.,Pettus, Benjamin J.,Pettus, Tobiah L.,Stringer, Joy Merry,Heasley, Victor L.,Syvret, Robert G.,Dobrolsky Jr., John M.
p. 1094 - 1098
(2007/10/03)

Electrochemical cleavage of allyl aryl ethers and allylation of carbonyl compounds: Umpolung of allyl-palladium species
The electrochemical, Pd-catalyzed cleavage of the C-O bond of allyl aryl ethers has been examined; the method constitutes a new alternative for allyl ether deprotection. The allyl transfer from the allyl ether to the carbonyl group in 2-allyloxy benzaldehydes is reported and is an example of allyl-Pd reactivity umpolung. Pd(II) complexes, associated to several nitrogen ligands are efficient catalyst precursors for these electrochemical reactions.
Franco,Panyella,Rocamora,Gomez,Clinet,Muller,Dunach
p. 5685 - 5688
(2007/10/03)

Zirconocene catalyzed dehalogenation of aromatic halides by alkylmagnesium reagents
When aromatic halides were treated with alkylmagnesium reagents (which have β-hydrogens) and a catalytic amount of zirconocene dichloride, dehalogenation proceeded smoothly in high yields. The stoichiometric dehalogenation using dialkylzir-conocenes also proceeded with high selectivities.
Hara, Ryuichiro,Sun, Wen-Hua,Nishihara, Yasushi,Takahashi, Tamotsu
p. 1251 - 1252
(2007/10/03)

Reaction of Aromatic and Unsaturated Compounds with the Potassium Permanganate/HCI (HBr) Acetonitrile Reagent
Addition of hydrochloric or hydrobromic acid to a solution of potassium permanganate in acetonitrile produced a homogeneous mixture, which is suitable for laboratory chlorination or bromination, respectively. Aromatic compounds more reactive than alkylbenzenes can be chlorinated or brominated without additional catalyst. Alkenes and alkynes give the corresponding vicinal dihaloalkanes and vinyl halides. All reactions complete within two hours under mild condition (25-60 °C) with excellent to moderate yields.
Liu, Lilian Kao,Lin, Ching-Shan
p. 61 - 66
(2007/10/03)

Optically active trans-2-aryl-1-cyclohexanol derivatives and a process for producing the compounds
The present invention provides an optically active trans-2-aryl-1-cyclohexanol derivative represented by the following general formula (I). STR1 The compounds can be obtained by transesterifiation reaction of the following compound (II) as a starting material with lipase. STR2 The optically active trans-2-aryl-1-cyclohexanol derivative can be used as an asymmetric source of asymmetric Diels-Alder reaction or a starting material of physiological active materials.
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(2008/06/13)

Nuclear versus Side-Chain Bromination of Methyl-Substituted Anisoles by N-Bromosuccinimide
The reactions of methyl-substituted anisoles with N-bromosuccinimide in CCl4 are reported.In the absence of a catalyst and under irradiation, some of these substrates undergo nuclear bromination in competition with the well-known side-chain bromination.With 2-methylanisole and with 2,6-dimethylanisole, nuclear bromination is not observed, whereas with 3,5-dimethylanisole, nuclear bromination at the 4-position is the dominating reaction.Investigation of the reactivity of several other methyl-substituted anisoles revealed the following general trend: methyl-substituted anisoles are attacked at the position para to the methoxy group rather than at the side chain when (at least) two methyl groups are present at positions 3 and 5.When positions 2 and 6 are both occupied, nuclear bromination is retarded; in 2,6-dimethylanisole and 2,3,6-trimethylanisole, only side-chain bromination is observed.In contrast, in 2,3,5,6-tetramethylanisole, the 4-position is sufficiently reactive to be brominated, because the decrease in reactivity by the presence of two methyl groups at positions 2 and 6 is overruled by the two additional methyl groups at positions 3 and 5; as a result, both nuclear and side-chain bromination occur.The observed chemospecificity can be rationalized by a difference in mechanism: the side-chain bromination is radical reaction, while the nuclear bromination is an electrophilic aromatic substitution reaction, which is so far contrary to expectation, as irradiation had been expected to favor radical processes.
Gruter, Gert-Jan M.,Akkerman, Otto S.,Bickelhaupt, Friedrich
p. 4473 - 4481
(2007/10/02)

Metal-Halogen Exchange between Polybromoanisoles and Aliphatic Grignard Reagents: A Synthesis of Cyclopentabenzofurans
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Nishiyama, Hisao,Isaka, Kojun,Itoh, Kenji,Ohno, Kiyotaka,Nagase, Hiroshi,et al.
p. 407 - 410
(2007/10/02)

ELECTROPHILIC BROMINATION OF PHENOL ETHERS IN SUPERACID SOLUTION USING ALKALI BROMIDE
Electrophilic aromatic bromination of phenol ethers in superacid medium can be achieved with sodium or potassium bromide. The yield and selectivity are lower than with bromine, the oxidation of the halide to the electrophilic halogen cation is obtained by concomitant reduction of antimony pentafluoride. Selectivity is observed only in methylanisole.
Cherry, Ghassan,Culmann, Jean-Christophe,Sommer, Jean
p. 2007 - 2010
(2007/10/02)

THE TRIFLUOROMETHYLATION OF CHLOROAROMATICS USING THE COPPER-CF2Br2-DIALKYLAMIDE REACTION SYSTEM
The in situ generation of CuCF3 from the reaction of copper, dibromodifluoromethane and either N,N-dimethylformamide or N,N-dimethylacetamide (Burton's reagent) has been used for the direct substitution of chlorine by CF3 in a number of aromatic substrates.Particular attention has been paid to the effects of ring substituents on the efficiency of reaction.
Clark, James H.,Denness, James E.,McClinton, Martin A.,Wynd, Andrew J.
p. 411 - 426
(2007/10/02)

Optically active liquid crystal compound having cyano group
An optically liquid crystalline compound having an extremely large spontaneous polarization value and a chiral smectic liquid crystal composition containing the compound are provided, the compound being expressed by the formula STR1 wherein m represents an integer of 2 to 18; l represents an integer of 0 to 12; n represents 0 or 1; R represents an alkyl group or an alkoxy group each of 2 to 20 carbon atoms, a halogen atom or cyano group; and A and B each represent a single bond, STR2 wherein X represents hydrogen atom, a halogen atom or cyano group, and a chiral smectic liquid crystal composition containing at least one kind of the above compound.
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(2008/06/13)

Aromatic Bromination Using BrF with No Friedel-Crafts Catalyst
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Rozen, Shlomo,Brand, Michael,Lidor, Rami
p. 5545 - 5547
(2007/10/02)

Halogenations of Aromatic Compounds with Halide Anions in the Presence of Nitrobenzenesulfonyl Peroxides. A Novel Method for the Formation of Positive Halogens
A novel type of positive halogens, sulfonyl hypochlorite or sulfonyl hypobromite was formed in the reactions of halide anions with nitrobenzenesulfonyl peroxides; these hypohalites could be used as effective reagents for halogenation of aromatic rings.
Yoshida, Masato,Mochizuki, Hideki,Kamigata, Nobumasa
p. 2017 - 2020
(2007/10/02)