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Imidazolium-urea low transition temperature mixtures for the UHP-promoted oxidation of boron compounds
Different carboxy-functionalized imidazolium salts have been considered as components of low transition temperature mixtures (LTTMs) in combination with urea. Among them, a novel LTTM based on 1-(methoxycarbonyl)methyl-3-methylimidazolium chloride and urea has been prepared and characterized by differential scanning calorimetry throughout its entire composition range. This LTTM has been employed for the oxidation of boron reagents using urea-hydrogen peroxide adduct (UHP) as the oxidizer, thus avoiding the use of aqueous H2O2, which is dangerous to handle. This metal-free protocol affords the corresponding alcohols in good to quantitative yields in up to 5 mmol scale without the need of further purification. The broad composition range of the LTTM allows for the reaction to be carried out up to three consecutive times with a single imidazolium salt loading offering remarkable sustainability with an E-factor of 7.9, which can be reduced to 3.2 by the threefold reuse of the system.
Martos, Mario,Pastor, Isidro M.
(2022/01/03)

Alkylsulfenyl thiocarbonates: precursors to hydropersulfides potently attenuate oxidative stress
The recent discovery of the prevalence of hydropersulfides (RSSH) species in biological systems suggests their potential roles in cell regulatory processes. However, the reactive and transient nature of RSSH makes their study difficult, and dependent on the use of donor molecules. Herein, we report alkylsulfenyl thiocarbonates as a new class of RSSH precursors that efficiently release RSSH under physiologically relevant conditions. RSSH release kinetics from these precursors are tunable through electronic modification of the thiocarbonate carbonyl group's electrophilicity. In addition, these precursors also react with thiols to release RSSH with a minor amount of carbonyl sulfide (COS). Importantly, RSSH generation by these precursors protects against oxidative stress in H9c2 cardiac myoblasts. Furthermore, we demonstrate the ability of these precursors to increase intracellular RSSH levels.
Aggarwal, Sahil C.,Khodade, Vinayak S.,Paolocci, Nazareno,Pharoah, Blaze M.,Toscano, John P.
p. 8252 - 8259
(2021/06/22)

Radical-anion coupling through reagent design: hydroxylation of aryl halides
The design and development of an oxime-based hydroxylation reagent, which can chemoselectively convert aryl halides (X = F, Cl, Br, I) into phenols under operationally simple, transition-metal-free conditions is described. Key to the success of this approach was the identification of a reducing oxime anion which can interact and couple with open-shell aryl radicals. Experimental and computational studies support the proposed radical-nucleophilic substitution chain mechanism.
Chechik, Victor,Greener, Andrew J.,James, Michael J.,Oca?a, Ivan,Owens-Ward, Will,Smith, George,Ubysz, Patrycja,Whitwood, Adrian C.
p. 14641 - 14646
(2021/11/17)

Predicting the hydrolytic breakdown rates of organophosphorus chemical warfare agent simulants using association constants derived from hydrogen bonded complex formation events
Organophosphorus (OP) chemical warfare agents (CWAs) represent an ongoing global threat, through either purposeful environmental release or the need to dispose of historic stockpiles. This presents a need for the development of novel decontamination technologies. Due to the toxic nature and legal limitations placed on OP CWAs, the use of appropriate OP simulants that mimic the reactivity but not the toxicity of the agents themselves is vital to decontamination studies. Herein, we show that association constants derived from non-specific hydrogen bonded complexation events may be used as parameters within models to predict simulant reactivity. We also discuss the limitations that should be placed on such data.
Chu, Dominique F.,Clark, Ewan R.,Ellaby, Rebecca J.,Hiscock, Jennifer,Pépés, Antigoni
(2021/11/22)

Decarboxylative Hydroxylation of Benzoic Acids
Herein, we report the first decarboxylative hydroxylation to synthesize phenols from benzoic acids at 35 °C via photoinduced ligand-to-metal charge transfer (LMCT)-enabled radical decarboxylative carbometalation. The aromatic decarboxylative hydroxylation is synthetically promising due to its mild conditions, broad substrate scope, and late-stage applications.
Ritter, Tobias,Su, Wanqi,Xu, Peng
p. 24012 - 24017
(2021/10/06)

Method for hydrolyzing diarylether compound to generate aryl phenol compound
The invention discloses a method for hydrolyzing a diarylether compound to generate an arylphenol compound. According to the method, visible light is utilized to excite a photosensitizer for catalysis. In a reaction solvent, the raw material in the formula (1) breaks a C (sp2)-O bond under the auxiliary action of acid, and hydrolysis is performed to obtain the bimolecular aryl phenol compounds in the formula (3) and the formula (4). The method can catalyze the reaction at room temperature, is green and environment-friendly, and is easy to operate; the universality is wide, the reaction yield is relatively high, and the tolerance of functional groups is strong; the synthesis method not only can realize small-scale hydrolysis conversion of various diarylether compounds, but also can realize hydrolysis of herbicidal ether, triclosan and a lignin template substrate, and even can realize large-scale hydrolysis of triclosan and the lignin template substrate to realize gram-level degradation. A new strategy is provided for recovering phenol derivatives through lignin hydrolysis, degrading pesticides and purifying wastewater containing a degerming agent or herbicide. The method has wide application prospect and use value.
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Paragraph 0135-0138

(2021/09/29)

Nickel-catalyzed deallylation of aryl allyl ethers with hydrosilanes
An efficient and mild catalytic deallylation method of aryl allyl ethers is developed, with commercially available Ni(COD)2 as catalyst precursor, simple substituted bipyridine as ligand and air-stable hydrosilanes. The process is compatible with a variety of functional groups and the desired phenol products can be obtained with excellent yields and selectivity. Besides, by detection or isolation of key intermediates, mechanism studies confirm that the deallylation undergoes η3-allylnickel intermediate pathway.
Ding, Guangni,Fan, Sijie,Wang, Jingyang,Wang, Yu,Wu, Xiaoyu,Xie, Xiaomin,Yang, Liqun,Zhang, Zhaoguo
supporting information

(2021/09/28)

Isotruxene-based porous polymers as efficient and recyclable photocatalysts for visible-light induced metal-free oxidative organic transformations
Two new isotruxene-based porous polymers were prepared and demonstrated to be highly efficient, metal-free heterogeneous photocatalysts for oxidative transformations using air as the mild oxidant under visible-light irradiation. Both catalysts show excellent recyclability. In addition, the reactions can be performed in water, further indicating the greenness of this method. This journal is
Zhang, Haowen,Zhang, Xiao,Zheng, Ying,Zhou, Cen
supporting information
p. 8878 - 8885
(2021/11/27)

The graphite-catalyzed: ipso -functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes
An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.
Badgoti, Ranveer Singh,Dandia, Anshu,Parewa, Vijay,Rathore, Kuldeep S.,Saini, Pratibha,Sharma, Ruchi
p. 18040 - 18049
(2021/05/29)

Biocatalytic Cross-Coupling of Aryl Halides with a Genetically Engineered Photosensitizer Artificial Dehalogenase
Devising artificial photoenzymes for abiological bond-forming reactions is of high synthetic value but also a tremendous challenge. Disclosed herein is the first photobiocatalytic cross-coupling of aryl halides enabled by a designer artificial dehalogenase, which features a genetically encoded benzophenone chromophore and site-specifically modified synthetic NiII(bpy) cofactor with tunable proximity to streamline the dual catalysis. Transient absorption studies suggest the likelihood of energy transfer activation in the elementary organometallic event. This design strategy is viable to significantly expand the catalytic repertoire of artificial photoenzymes for useful organic transformations.
Fu, Yu,Huang, Jian,Wu, Yuzhou,Liu, Xiaohong,Zhong, Fangrui,Wang, Jiangyun
supporting information
p. 617 - 622
(2021/02/03)

Method for preparing alcohol and phenol through aerobic hydroxylation reaction of boric acid derivative in absence of photocatalyst
The invention discloses a method for preparing alcohol and phenol through aerobic hydroxylation reaction of a boric acid derivative in the absence of a photocatalyst, wherein the boric acid derivativeis aryl boronic acid or alkyl boronic acid, and the corresponding target compounds are respectively a phenol-based compound and an alcohol-based compound. According to the method, by using a boric acid derivative as a reaction substrate, an additive is added under a solvent condition, and a hydroxylation reaction is performed under aerobic and illumination conditions to obtain a corresponding target compound. According to the invention, the new strategy is provided for the synthesis of phenols through aerobic hydroxylation of aryl boronic acid without a photocatalyst; the catalyst-free aerobic hydroxylation method for photocatalysis of aryl boronic acid or alkyl boronic acid by using triethylamine as an additive is firstly disclosed; and the new method has advantages of photocatalyst-freecondition, wide substrate range and good functional group compatibility.
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Paragraph 0025-0028; 0030-0032

(2020/01/25)

Visible-light-promoted aerobic oxidative hydroxylation of arylboronic acids in water by hydrophilic organic semiconductor
A green and sustainable catalytic system was developed based on perylenediimide (PDI) organic semiconductor for the aerobic oxidative hydroxylation of arylboronic acids in aqueous solution with visible light. By using PDI-SN, a hydrophilic organic semiconductor, which can activate oxygen to produce superoxide radicals in aqueous solution, this reaction proceeds under ambient conditions: water as the solvent and air as the oxidant, giving various phenols as products with high yields. In contrast to methods using organic solvents, this novel process has the potential of green industrial application.
Yu, Kunyi,Zhang, Hanjie,Sheng, Yuqiang,Zhu, Yongfa
supporting information

(2020/06/23)

Aerobic photooxidative hydroxylation of boronic acids catalyzed by anthraquinone-containing polymeric photosensitizer
We report herein the synthesis of a polymeric photosensitizer and its application in aerobic photooxidative hydroxylation of boronic acids. The polymeric photosensitizer was synthesized by the condensation of anthraquinone-2-carbonyl chloride (AQ-2-COCl) with poly (2-hydroxyethyl methacrylate) (PHEMA). The photo-oxidative hydroxylation of boronic acids using anthraquinone-containing-poly (2-hydroxyethyl methacrylate) (AQ-PHEMA) was then explored and shown to exhibit high efficiency and broad scope. Moreover, AQ-PHEMA could be easily recovered and reused for more than 20 times without significant loss of the catalytic activity.
Chen, Yang,Ding, Aishun,Hu, Jianhua
p. 7927 - 7932
(2020/03/11)

Quaternary ammonium hydroxide-functionalized g-C3N4 catalyst for aerobic hydroxylation of arylboronic acids to phenols
A new and efficient metal-free approach toward the synthesis of phenols via an aerobic hydroxylation of arylboronic acids by using a novel quaternary ammonium hydroxide g-C3N4 catalyst has been described. The functionalized quaternary ammonium hydroxide (g-C3N4-OH) has been prepared from graphitic carbon nitride (g-C3N4) scaffold by converting the residual –NH2 and –NH groups to quaternary methyl ammonium iodide by performing a methylation reaction with methyl iodide followed by ion-exchange with 0.1 N KOH or anion exchange resin Amberlyst A26 (OH- form) by post-synthetic modification. The resultant g-C3N4-OH was characterized by XRD, FTIR, field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), N2 adsorption/desorption isotherms, and acid–base titration. Tested as solid-base catalysts, the g-C3N4-OH showed excellent catalytic activity in the aerobic hydroxylation reaction by converting a variety of arylboronic acids to the corresponding phenols in high yields. More importantly, the g-C3N4-OH solid-base has been successfully reused four times with the minor loss of initial catalytic activity (10.5percent).
Muhammad, Ibrahim,Mannathan, Subramaniyan,Sasidharan, Manickam
p. 1470 - 1476
(2020/07/13)

Glass wool supported ruthenium complexes: Versatile, recyclable heterogeneous photoredox catalysts
The present study describes the development of heterogeneous photoredox catalysts based on ruthenium complexes anchored onto a glass surface (glass wool). These easy-to-handle, inexpensive and reusable fiber-like materials allow Ru-based photoredox catalysis in the heterogeneous phase. Here we report the synthesis and characterization of these new materials, and evaluate their remarkable photocatalytic activity to engage in aerobic photooxidative reactions. In particular, the oxidative hydroxylation of arylboronic acids and the singlet oxygen-mediated photooxidation of 9,10-dimethylanthracene (DMA) and 2-ethylfuran are achieved with excellent yields (>95%) within 6 h of irradiation using blue LEDs (λ ～ 450 nm). Further, the materials can be reused at least 6 times without any significant loss of activity, thus revealing their high stability and recyclability. The strategy takes advantage of the broad knowledge on Ru-based photocatalysis while adding the recovery and reuse benefits of heterogeneous catalysis. Additionally, these materials are promising alternatives for flow photochemistry. This approach that allows attachment of Ru complexes onto glass wool can be extended for use to other transition-metal complexes as photoredox catalysts.
De Lucas, Nanci C.,Garden, Simon J.,Lanterna, Anabel E.,Scaiano, Juan C.,Teixeira, Rodolfo I.
p. 1273 - 1280
(2020/03/26)

A Unified and Practical Method for Carbon–Heteroatom Cross-Coupling using Nickel/Photo Dual Catalysis
While carbon–heteroatom cross-coupling reactions have been extensively studied, many methods are specific and limited to a particular set of substrates or functional groups. Reported here is a general method that allows for C?O, C?N and C?S cross-coupling reactions under one general set of conditions. We propose that an energy transfer pathway, in which an iridium photosensitizer produces an excited nickel(II) complex, is responsible for the key reductive elimination step that couples aryl bromides, iodides, and chlorides to 1° and 2° alcohols, amines, thiols, carbamates, and sulfonamides, and is amenable to scale up via a flow apparatus.
Escobar, Randolph A.,Johannes, Jeffrey W.
supporting information

(2020/04/17)

Visible light-catalytic hydroxylation of aryl halides with water to phenols by carbon nitride and nickel complex cooperative catalysis
The efficient conversion of aryl halides to phenols under mild reaction conditions remains a great challenge. Here we demonstrate that a facile and efficient hydroxylation reaction of aryl halides with water could be accomplished through a merger of a heterogeneous organic semiconductor graphitic carbon nitride (g-C3N4) photocatalyst and a homogeneous nickel(ii) bipyridine organometallic catalyst under visible-light irradiation at room temperature. The protocol is tolerant to a wide range of substituted aryl halides, resulting in various phenol products with excellent conversion and selectivity. It is worth noting that the OH group of the resulting phenols originating from water increased the environmental friendliness of the reaction. It is worth noting that among all the previously reported catalysts (even including thermal catalysts with harsh reaction conditions), our Nidabpy/g-C3N4 dual catalytic system demonstrated the highest catalytic activity reported in the shortest reaction time. This remarkable catalytic performance was attributed to the strong interaction between the Nidabpy complex and g-C3N4, which decreased the transfer distance of photogenerated electrons transferring to Ni(ii), accelerating the catalytic cycle. Furthermore, g-C3N4 was easily recovered from the reaction mixture and reused five times, showing the good potential of green hydroxylation reactions for large-scale industrial application.
Li, Hexing,Liu, Helong,Tong, Min,Wang, Kaixuan,Yang, Yanan,Zhang, Bingyu,Zhang, Fang
p. 7417 - 7423
(2020/11/19)

Photoinduced Hydroxylation of Organic Halides under Mild Conditions
Presented in this paper is photoinduced hydroxylation of organic halides, providing a mild access to a range of functionalized phenols and aliphatic alcohols. These reactions generally proceed under mild reaction conditions with no need for a photocatalyst or a strong base and show a wide substrate scope as well as excellent functional group tolerance. This work highlights the unique role of NaI that allows a challenging transformation to proceed under mild reaction conditions.
Cai, Yue-Ming,Xu, Yu-Ting,Zhang, Xin,Gao, Wen-Xia,Huang, Xiao-Bo,Zhou, Yun-Bing,Liu, Miao-Chang,Wu, Hua-Yue
supporting information
p. 8479 - 8484
(2019/10/16)

Semi-heterogeneous Dual Nickel/Photocatalysis using Carbon Nitrides: Esterification of Carboxylic Acids with Aryl Halides
Cross-coupling reactions mediated by dual nickel/photocatalysis are synthetically attractive but rely mainly on expensive, non-recyclable noble-metal complexes as photocatalysts. Heterogeneous semiconductors, which are commonly used for artificial photosynthesis and wastewater treatment, are a sustainable alternative. Graphitic carbon nitrides, a class of metal-free polymers that can be easily prepared from bulk chemicals, are heterogeneous semiconductors with high potential for photocatalytic organic transformations. Here, we demonstrate that graphitic carbon nitrides in combination with nickel catalysis can induce selective C?O cross-couplings of carboxylic acids with aryl halides, yielding the respective aryl esters in excellent yield and selectivity. The heterogeneous organic photocatalyst exhibits a broad substrate scope, is able to harvest green light, and can be recycled multiple times. In situ FTIR was used to track the reaction progress to study this transformation at different irradiation wavelengths and reaction scales.
Pieber, Bartholom?us,Malik, Jamal A.,Cavedon, Cristian,Gisbertz, Sebastian,Savateev, Aleksandr,Cruz, Daniel,Heil, Tobias,Zhang, Guigang,Seeberger, Peter H.
supporting information
p. 9575 - 9580
(2019/06/25)

Tetrafluoropyridyl (TFP): a general phenol protecting group readily cleaved under mild conditions
Phenols are extremely valuable building blocks in the areas of pharmaceuticals, natural products, materials and catalysts. In order to carry out modifications on phenols, the phenolic oxygen is routinely protected to prevent unwanted side reactions. Presently many of the protecting groups available can require harsh conditions, specialist equipment, expensive or air/moisture-sensitive reagents to install and remove. Here we introduce the use of the tetrafluoropyridyl (TFP) group as a general protecting group for phenols. TFP can be installed in one step with no sensitivity to water or air, and it is stable under a range of commonly employed reaction conditions including acid and base. The TFP protecting group is readily cleaved under mild conditions with quantitative conversion to the parent phenol, observed in many cases in less than 1 hour.
Brittain, William D. G.,Cobb, Steven L.
supporting information
p. 2110 - 2115
(2019/02/27)

Regioselectivity of Hydroxyl Radical Reactions with Arenes in Nonaqueous Solutions
The regioselectivity of hydroxyl radical addition to arenes was studied using a novel analytical method capable of trapping radicals formed after the first elementary step of reaction, without alteration of the product distributions by secondary oxidation processes. Product analyses of these reactions indicate a preference for o- over p-substitution for electron donating groups, with both favored over m-addition. The observed distributions are qualitatively similar to those observed for the addition of other carbon-centered radicals, although the magnitude of the regioselectivity observed is greater for hydroxyl. The data, reproduced by high accuracy CBS-QB3 computational methods, indicate that both polar and radical stabilization effects play a role in the observed regioselectivities. The application and potential limitations of the analytical method used are discussed.
Moores, Lee C.,Kaur, Devinder,Smith, Mathew D.,Poole, James S.
supporting information
p. 3260 - 3269
(2019/03/11)

Versatile catalysis of “natural extract”: oxidation of sulfides and alcohols and ipso-hydroxylation of arylboronic acids
Abstract: In the present work, we have described the versatile applications of naturally available inexpensive citrous lemon juice as biocatalyst for controlled oxidation of sulfides and alcohols and ipso-hydroxylation of arylboronic acids using 30% H2O2 as a green oxidant. A series of structurally divergent sulfides and benzyl alcohols were oxidized to their corresponding sulfoxides and aldehydes, respectively, with good-to-excellent yields. Similarly, aryl and heteroaryl boronic acids were rapidly, often within minutes, transformed to their corresponding phenols at room temperature. Graphic abstract: [Figure not available: see fulltext.]
Dutta, Apurba,Ali, Abdul Aziz,Sarma, Diganta
p. 2379 - 2388
(2019/06/28)

Phthalocyanine Zinc-catalyzed Hydroxylation of Aryl Boronic Acids under Visible Light
A visible-light-promoted aerobic oxidative hydroxylation of boronic acids using phthalocyanine zinc as an easily available photosensitizer has been developed. It provided a direct access to synthesize aliphatic alcohols and phenols from boronic acids. The advantages of this approach included the low catalyst loading (0.5 mol%), high efficient, the use of O2 as an oxygen source, wide substrate range, the simple operational process, and mild conditions. (Figure presented.).
Luo, Dong-Ping,Huang, Yang-Feng,Hong, Xiao-Yi,Chen, Dingben,Li, Guo-Xing,Huang, Xiao-Bo,Gao, Wen-Xia,Liu, Miao-Chang,Zhou, Yun-Bing,Wu, Hua-Yue
supporting information
p. 961 - 964
(2019/01/25)

Photoinduced hydroxylation of arylboronic acids with molecular oxygen under photocatalyst-free conditions
Photoinduced hydroxylation of boronic acids with molecular oxygen under photocatalyst-free conditions is reported, providing a green entry to a variety of phenols and aliphatic alcohols in a highly concise fashion. This new protocol features photocatalyst-free conditions, wide substrate scope and excellent functional group compatibility.
Xu, Yu-Ting,Li, Chen-Yuan,Huang, Xiao-Bo,Gao, Wen-Xia,Zhou, Yun-Bing,Liu, Miao-Chang,Wu, Hua-Yue
supporting information
p. 4971 - 4975
(2019/09/30)

Potassium: Tert -butoxide mediated aerobic hydroxylation of arylboronic acids: An application towards the synthesis of (E)-phenoxy acrylates
The first example of potassium tert-butoxide mediated aerobic hydroxylation of arylboronic acids is described. A variety of arylboronic acids bearing both electron donating and withdrawing substituents successfully participated in the reaction and furnished phenols in good yields. This strategy also provides access to one pot synthesis of (E)-3-phenoxy acrylates from arylboronic acids and propiolates. The solvent plays an important role and a binary solvent system comprising CH3CN/THF is found to be the best.
Muhammad, Ibrahim,Balakrishnan, Madasamy Hari,Sasidharan, Manickam,Mannathan, Subramaniyan
supporting information
p. 11065 - 11068
(2019/07/31)

Trichloroacetonitrile as an efficient activating agent for the: Ipso -hydroxylation of arylboronic acids to phenolic compounds
A metal-free and base-free Cl3CCN mediated method was developed for the ipso-hydroxylation of aryl boronic acids to their corresponding phenols, which was promoted by a key unstable Lewis adduct intermediate. This transformation has broad functional group tolerance, and late-stage functionalization was successful as well. After simple investigation, two pathways (radical/ionic mechanism) were suggested, and the beneficial action of blue light needs to be further studied.
Fang, Yuanding,Zhao, Rong,Yao, Yuan,Liu, Yang,Chang, Denghu,Yao, Ming,Shi, Lei
p. 7558 - 7563
(2019/08/20)

Solar-driven conversion of arylboronic acids to phenols using metal-free heterogeneous photocatalysts
Solar-driven conversion of arylboronic acids to phenols was achieved by employing graphitic carbon nitride (g-C3N4) as heterogeneous photocatalyst, where [rad]O2? was the main active species. By loading g-C3N4 onto the easy weaving low melting point sheath-core composite polyester fibers (LMPET), g-C3N4-based artificial photosynthetic catalytic fabric (g-C3N4/LMPET) with a large light receiving area was prepared. It displayed the efficient conversion of arylboronic acid and excellent recycling performance. This system offers more possibilities to construct an artificial photosynthetic system with excellent solar-to-chemicals conversion efficiency.
Xu, Tiefeng,Lu, Wangyang,Wu, Xiao-Feng,Chen, Wenxing
p. 63 - 67
(2019/09/10)

Electrochemically Driven, Ni-Catalyzed Aryl Amination: Scope, Mechanism, and Applications
C-N cross-coupling is one of the most valuable and widespread transformations in organic synthesis. Largely dominated by Pd- and Cu-based catalytic systems, it has proven to be a staple transformation for those in both academia and industry. The current study presents the development and mechanistic understanding of an electrochemically driven, Ni-catalyzed method for achieving this reaction of high strategic importance. Through a series of electrochemical, computational, kinetic, and empirical experiments, the key mechanistic features of this reaction have been unraveled, leading to a second generation set of conditions that is applicable to a broad range of aryl halides and amine nucleophiles including complex examples on oligopeptides, medicinally relevant heterocycles, natural products, and sugars. Full disclosure of the current limitations and procedures for both batch and flow scale-ups (100 g) are also described.
Kawamata, Yu,Vantourout, Julien C.,Hickey, David P.,Bai, Peng,Chen, Longrui,Hou, Qinglong,Qiao, Wenhua,Barman, Koushik,Edwards, Martin A.,Garrido-Castro, Alberto F.,Degruyter, Justine N.,Nakamura, Hugh,Knouse, Kyle,Qin, Chuanguang,Clay, Khalyd J.,Bao, Denghui,Li, Chao,Starr, Jeremy T.,Garcia-Irizarry, Carmen,Sach, Neal,White, Henry S.,Neurock, Matthew,Minteer, Shelley D.,Baran, Phil S.
supporting information
p. 6392 - 6402
(2019/04/17)

Synthesis of phenols and aryl silyl ethers via arylation of complementary hydroxide surrogates
Two transition-metal-free methods to access substituted phenols via the arylation of silanols or hydrogen peroxide with diaryliodonium salts are presented. The complementary reactivity of the two nucleophiles allows synthesis of a broad range of phenols without competing aryne formation, as illustrated by the synthesis of the anesthetic Propofol. Furthermore, silyl-protected phenols can easily be obtained, which are suitable for further transformations.
Reitti, Marcus,Gurubrahamam, Ramani,Walther, Melanie,Lindstedt, Erik,Olofsson, Berit
p. 1785 - 1788
(2018/04/14)

Aryl trifluoromethylation of the compound of preparation method and application
The invention discloses a aryl trifluoromethylation of the compound of preparation method and application. The preparation method comprises: the illumination and under alkaline conditions, making compound A and trifluoromethyl reagent in organic solvent containing the catalyst in the reaction system, to obtain the aryl trifluoromethylation of composition; A of the compounds shown in the following formula: A, The compound of the structural formula A in R is alkyl, alkoxy, hydroxy, halogen, nitro, carboxyl in the one or more than two. Preparation method of this invention the reaction condition is simple, only requiring illumination of the reaction material, the effect of the catalyst and the alkaline condition, can obtain the aryl trifluoromethylation of composition, preparation process does not need ligand, without precursor compound, product without catalyst residue.
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Paragraph 0059; 0061; 0063; 0064

(2018/07/15)

Diverse copper(iii) trifluoromethyl complexes with mono-, bi- and tridentate ligands and their versatile reactivity
Cu(iii) trifluoromethyl complexes are proposed as essential intermediates for many copper-promoted trifluoromethylation reactions, but remain elusive and scarcely explored. We report herein the isolation and spectroscopic and X-ray crystallographic charac
Zhang, Song-Lin,Xiao, Chang,Wan, Hai-Xing
supporting information
p. 4779 - 4784
(2018/04/11)

Recyclable CNT-chitosan nanohybrid film utilized in copper-catalyzed aerobic ipso-hydroxylation of arylboronic acids in aqueous media
A convenient heterogeneous catalytic system consisting of recyclable and reusable carbon nanotube-chitosan nanohybrid film and copper salt was developed for the aerobic ipso-hydroxylation of arylboronic acids. A variety of arylboronic acids bearing electron-withdrawing or electron-donating groups were smoothly transformed at room temperature in water to afford the corresponding phenols in high yields.
Kim, Han-Sem,Joo, Sung-Ryu,Shin, Ueon Sang,Kim, Seung-Hoi
p. 4597 - 4601
(2018/11/23)

Picosecond Electron Transfer from Quantum Dots Enables a General and Efficient Aerobic Oxidation of Boronic Acids
General visible light-mediated aerobic oxidation of boronic acids is unveiled using CdSe nanocrystal quantum dots (QDs) as the photoredox catalyst. This protocol requires mild reaction conditions and low catalyst loading (down to 10 ppm), and tolerates various functional groups. The resulting phenols and aliphatic alcohols are produced in good to high yield with turnover numbers as high as >62000. The reaction mechanism is probed using ultrafast transient absorption and luminescence spectroscopy. The existence of a rapid 350 ps initial electron transfer followed by a hole transfer is demonstrated.
Simlandy, Amit Kumar,Bhattacharyya, Biswajit,Pandey, Anshu,Mukherjee, Santanu
p. 5206 - 5211
(2018/05/15)

Method for synthesizing 2-chlorine-4-trifluoromethyl phenol
The invention discloses a method for synthesizing 2-chlorine-4-trifluoromethyl phenol. The method comprises the following steps: (1) carrying out an oxidation reaction, namely enabling 4-(trifluoromethyl) benzaldehyde, an organic solvent and an oxidant to react at 0 DEG C or a higher temperature in a reaction container so as to obtain 4-(trifluoromethyl) phenol; (2) carrying out a halogenation reaction, namely in the presence of an inert gas, adding a halogenation reagent and an organic solvent into another reaction container, sequentially adding a catalyst and the 4-(trifluoromethyl) phenol obtained in the step (1) at a low temperature, and stirring at a room temperature to enable the components to react, thereby obtaining 2-chlorine-4-trifluoromethyl phenol. The method is relatively highin raw material availability, relatively less in byproduct amount, low in pollution, and relatively short in reaction time, and has the characteristics that the operation is simple and convenient, products and reaction systems can be easily separated, aftertreatment is convenient and rapid, the obtained product is relatively high in purity, and the like, the yield is greatly improved, and a reliable foundation is provided for industrial production.
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Paragraph 0012; 0013; 0014; 0015

(2018/07/30)

Synthetic method of fomesafen intermediate 2-chloro-4-trifluoromethylphenol
The invention relates to a synthetic method of fomesafen intermediate 2-chloro-4-trifluoromethylphenol. 4-(Trifluoromethyl)benzaldehyde is used as a reaction material; mCPBA (meta-chloroperoxybenzoicacid) is used as an oxidant to convert 4-(trifluoromethyl)benzaldehyde into 4-(trifluoromethyl)phenol; NCS (N-chlorosuccinimide) is used to subject 4-(trifluoromethyl)benzaldehyde to chlorination to obtain the intermediate 2-chloro-4-trifluoromethylphenol. The method has the advantages that, for instance, the materials are easy to obtain, few byproducts are produced, little pollution is caused, reaction time is short and the yield is high.
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Paragraph 0025; 0026; 0027; 0028

(2018/04/27)

Mechanistic Insight into Weak Base-Catalyzed Generation of Carbon Monoxide from Phenyl Formate and Its Application to Catalytic Carbonylation at Room Temperature without Use of External Carbon Monoxide Gas
The mechanisms of the weak base-catalyzed generation of carbon monoxide (CO) and phenol from phenyl formate were investigated by experimental and theoretical methods. Kinetic studies revealed a first-order reaction in both phenyl formate and the base. The reaction was found to proceed by an E2 α-elimination pathway, which involves the abstraction of the formyl proton of phenyl formate, simultaneously generating CO and phenoxide. The reaction rate was affected by the substituents on phenyl formate, the polarity of solvents, and the basicity of bases. The mechanistic insight obtained from these studies permitted the chemical control of the rate of CO generation, which was the key to the development of the external CO-free Pd-catalyzed phenoxycarbonylation of haloarenes at room temperature. Because of the mild reaction conditions and wide substrate scope, this phenoxycarbonylation constitutes a general, safe, and practical method to synthesize arenecarboxylic acid esters. (Figure presented.).
Konishi, Hideyuki,Matsubara, Mika,Mori, Keisuke,Tokiwa, Takaki,Arulmozhiraja, Sundaram,Yamamoto, Yuta,Ishikawa, Yoshinobu,Hashimoto, Hiroshi,Shigeta, Yasuteru,Tokiwa, Hiroaki,Manabe, Kei
p. 3592 - 3601
(2017/10/24)

Mechanistic Investigations of the Hydrogenolysis of Diaryl Ethers Catalyzed by Nickel Complexes of N-Heterocyclic Carbene Ligands
Recent interest in the valorization of lignin has led to reactions involving the cleavage of strong aromatic C-O bonds. However, few experimental mechanistic studies of these reactions have been published. We report detailed mechanistic analysis of the hydrogenolysis of diaryl ethers catalyzed by the combination of Ni(COD)2 (COD = 1,5-cyclooctadiene) and an N-heterocyclic carbene (NHC). Experiments on the catalytic reaction indicated that NaOt-Bu was necessary for catalysis, but kinetic analysis showed that the base is not involved in the rate-limiting C-O bond cleavage. The resting state of the catalyst is an NHC-Ni(η6-arene) complex. Substitution of the coordinated solvent with diaryl ether allowed isolation of a diaryl ether-bound Ni complex. Rate-limiting C-O bond cleavage occurs to generate a three-coordinate product of oxidative addition, a metallacyclic version of which has been prepared independently. Stoichiometric studies show that arene and phenol products are released following reaction with H2. NaOt-Bu was found to deprotonate the phenol product and to prevent formation of inactive NiI dimers.
Saper, Noam I.,Hartwig, John F.
supporting information
p. 17667 - 17676
(2017/12/15)

Facile and metal-free synthesis of phenols from benzaldoxime and diaryliodonium salts
A metal-free, base-promoted facile synthesis of phenol derivatives utilising diaryliodonium salts as the aryl source and benzaldoxime as the hydroxide surrogate has been developed. The reaction is fast and shows good substrate compatibility, giving the corresponding products in good to excellent yields. A gram-scale synthesis of phenols utilising this protocol has also been achieved.
Zhou, Yongsheng
p. 591 - 593
(2017/11/14)

Facile and effective approach for oxidation of boronic acids
This present work illustrates facile and effective approach for oxidation of boronic acids using environmentally benign dimethyl carbonate (DMC) as a solvent with H2O2 as an oxidant at room temperature. In contrast to previous reaction reports, which make use of metal catalyst, hazardous reagent and oxidants that creates environmental concern. This method provides good to excellent yield of products and showed better tolerance towards various functional groups present on boronic acids. Moreover, this developed process is an alternative in terms of inexpensive, non toxic and easy reaction conditions.
Wagh, Ravindra B.,Nagarkar, Jayashree M.
supporting information
p. 4572 - 4575
(2017/11/03)

Silica chloride: An efficient promoter for oxidation of arylboronic acids to phenols
This work reports simple, highly efficient protocol for the oxidation of arylboronic acids. Various arylboronic acids were selectively and completely converted into their corresponding oxidized phenols using H2O2 as an oxidant in presence of catalytic amount of silica chloride. The results show that silica chloride is a suitable and efficient promoter for the oxidation of arylboronic acids. Heterogeneous catalyst, mild reaction conditions, easy availability of the reagent, easy work-up, excellent yield of corresponding phenols, short reaction time and broad substrate scope makes this protocol attractive and a practical alternative to the existing methods.
Wagh, Ravindra B.,Nagarkar, Jayashree M.
supporting information
p. 3323 - 3326
(2017/07/27)

Pd-Catalyzed Hydroxylation of Aryl Boronic Acids Using In Situ Generated Hydrogen Peroxide
Herein, we describe a benign and efficient palladium-catalyzed hydroxylation of aryl boronic acids under mild conditions, with in situ generated hydrogen peroxide from carbon monoxide, water, and oxygen. This novel procedure combines catalytic production of hydrogen peroxide with an aerobic oxidation process in a sole reaction system. This system shows good functional group tolerance and provides a benign and efficient access to a variety of functionalized phenols. Furthermore, the in situ generated hydroperoxide can be well used for triphenylphosphine oxidation, in which the TON is up to 194. Isotope labelling studies provide important mechanistic insights for this process.
Yi, Hong,Lei, Aiwen
supporting information
p. 10023 - 10027
(2017/08/01)

Polymer-Supported Photosensitizers for Oxidative Organic Transformations in Flow and under Visible Light Irradiation
A 2,1,3-benzothiadiazole (BTZ)-based vinyl cross-linker was synthesized and copolymerized with large excesses of styrene using free radical polymerization to deliver heterogeneous triplet photosensitizers in three distinct physical formats: gels, beads, and monoliths. These photosensitizers were employed for the production of singlet oxygen (1O2) and for the aerobic hydroxylation of arylboronic acids via superoxide radical anion (O2?-), whereby the materials demonstrated good chemical and light stability. BTZ-containing beads and monoliths were exploited as photosensitizers in a commercial flow reactor, and 1O2 production was also demonstrated using direct sunlight irradiation, with a conversion rate comparable to the rates achieved when a 420 nm LED module is used as the source of photons.
Tobin, John M.,McCabe, Timothy J. D.,Prentice, Andrew W.,Holzer, Sarah,Lloyd, Gareth O.,Paterson, Martin J.,Arrighi, Valeria,Cormack, Peter A. G.,Vilela, Filipe
p. 4602 - 4612
(2017/07/24)

Cobalt-Catalyzed Oxidative Homocoupling of Arylzinc Species
A novel procedure for the synthesis of functionalized symmetrical biaryl compounds is described. The reaction proceeds via the oxidative homocoupling of arylzinc species formed by cobalt catalysis in the presence of air or p-benzoquinone depending on the nature of the functional group.
Bourne-Branchu, Yann,Moncomble, Aurélien,Corpet, Martin,Danoun, Gregory,Gosmini, Corinne
p. 3352 - 3356
(2016/09/12)

A versatile approach for the synthesis of para -substituted arenes via palladium-catalyzed C-H functionalization and protodecarboxylation of benzoic acids
While a great number of ortho C-H functionalization reactions have been developed and several breakthroughs have been achieved in meta C-H activation, para C-H functionalization is still in its infancy stage. In this article, a versatile strategy for the synthesis of para-substituted arenes has been developed via a tandem process consisting of palladium-catalyzed C-H functionalization and subsequent copper-catalyzed protodecarboxylation of benzoic acids. Both electron-withdrawing and electron-donating functionalities can be introduced into the para positions of arenes bearing a variety of substituents.
Pan, Shulei,Zhou, Bo,Zhang, Yanghui,Shao, Changdong,Shi, Guangfa
supporting information
p. 277 - 281
(2016/01/20)

Visible-Light Photoredox Borylation of Aryl Halides and Subsequent Aerobic Oxidative Hydroxylation
Efficient and practical visible-light photoredox borylation of aryl halides and subsequent aerobic oxidative hydroxylation were developed. The protocols use readily available aryl halides and bis(pinacolato)diboron as the starting materials, fac-Ir(ppy)3 as the photocatalyst, and corresponding arylboronic esters and phenols were obtained in good yields. The methods show some advantages including simple equipment, mild conditions, easy operation, and wide substrate scope. Therefore, they should provide a valuable strategy for chemical transformations.
Jiang, Min,Yang, Haijun,Fu, Hua
supporting information
p. 5248 - 5251
(2016/11/02)

Development of a novel sulfonate ester-based prodrug strategy
A self-immolative γ-aminopropylsulfonate linker was investigated for use in the development of prodrugs that are reactive to various chemical or biological stimuli. To demonstrate their utility, a leucine-conjugated prodrug of 5-chloroquinolin-8-ol (5-Cl-8-HQ), which is a potent inhibitor against aminopeptidase from Aeromonas proteolytica (AAP), was synthesized. The sulfonate prodrug was considerably stable under physiological conditions, with only enzyme-mediated hydrolysis of leucine triggering the subsequent intramolecular cyclization to simultaneously release 5-Cl-8-HQ and form γ-sultam. It was also confirmed that this γ-aminopropylsulfonate linker was applicable for prodrugs of not only 8-HQ derivatives but also other drugs bearing a phenolic hydroxy group.
Hanaya, Kengo,Yoshioka, Shohei,Ariyasu, Shinya,Aoki, Shin,Shoji, Mitsuru,Sugai, Takeshi
supporting information
p. 545 - 550
(2016/01/09)

TCDA: Practical Synthesis and Application in the Trifluoromethylation of Arenes and Heteroarenes
A practical synthesis of the reagent trimethylsilyl chlorodifluoroacetate (TCDA) is reported on 50 g scale. The trifluoromethylation with TCDA was optimized, and the reaction shows very broad scope with respect to electron-deficient, -neutral, -rich aryl/heteroaryl iodides, as well as excellent functional group tolerability, such as ester, amide, aldehyde, hydroxyl, and carboxylic acid. The reagent was also applied to the late-stage trifluoromethylation of three medicinally relevant compounds. Additionally, the building block trifluoromethylpyridine and one drug related molecule Boc-Fluoxetin were synthesized in 10 g scale by this method, demonstrating its practical applications in process chemistry.
Wang, Jian,Zhang, Xiaomin,Wan, Zehong,Ren, Feng
p. 836 - 839
(2016/05/19)

Cu3(BTC)2 as heterogeneous catalyst for the room temperature oxidative hydroxylation of arylboronic acids
A well known copper based-metal organic framework (MOF), namely Cu3(BTC)2, is a suitable heterogeneous catalyst to promote the oxidative room-temperature hydroxylation of arylboronic acids to the corresponding phenols by H2O2. Using 0.5 equiv of H2O2, Cu3(BTC)2 exhibits 80% conversion in 60 min that is higher than 70% conversion achieved with Fe(BTC) under the same conditions and reaction time. Cu3(BTC)2 is reusable with no significant drop in the activity. Furthermore, powder XRD of the reused Cu3(BTC)2 shows no changes in crystallinity compared to the fresh Cu3(BTC)2, indicating catalyst stability is maintained under reaction conditions. The scope of Cu3(BTC)2 as heterogeneous catalyst for the oxidative hydroxylation was studied for various phenylboronic acids.
Dhakshinamoorthy, Amarajothi,Asiri, Abdullah M.,Garcia, Hermenegildo
p. 2895 - 2899
(2016/05/19)

New Reagent for Highly Efficient Synthesis of Trifluoromethyl-Substituted Arenes and Heteroarenes
A new reagent trimethylsilyl chlorodifluoroacetate (TCDA) is reported for the introduction of a -CF3 group to arenes and heteroarenes. Compared with current known reagents, TCDA shows very broad scope with respect to electron-deficient, -neutral, and -rich aryl/heteroaryl iodides as well as excellent functional group tolerance, including ester, amide, aldehyde, hydroxyl, and carboxylic acid. (Chemical Equation Presented).
Zhang, Xiaomin,Wang, Jian,Wan, Zehong
supporting information
p. 2086 - 2089
(2015/05/13)

Solvent-free one-step photochemical hydroxylation of benzene derivatives by the singlet excited state of 2,3-dichloro-5,6-dicyano-p-benzoquinone acting as a super oxidant
Photoinduced hydroxylation of neat deaerated benzene to phenol occurred under visible-light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), which acts as a super photooxidant in the presence of water. Photocatalytic solvent-free hydroxylation of benzene derivatives with electron-withdrawing substituents such as benzonitrile, nitrobenzene, and trifluoromethylbenzene used as neat solvents has been achieved for the first time by using DDQ as a super photooxidant to yield the corresponding phenol derivatives and 2,3-dichloro-5,6-dicyanohydroquinone (DDQH2) in the presence of water under deaerated conditions. In the presence of dioxygen and tert-butyl nitrite, the photocatalytic hydroxylation of neat benzene occurred with DDQ as a photocatalyst to produce phenol. The photocatalytic reactions are initiated by oxidation of benzene derivatives with the singlet and triplet excited states of DDQ to form the corresponding radical cations, which associate with benzene derivatives to produce the dimer radical cations, which were detected by the femto- and nanosecond laser flash photolysis measurements to clarify the photocatalytic reaction mechanisms. Radical cations of benzene derivatives react with water to yield the OH-adduct radicals. On the other hand, DDQC?- produced by the photoinduced electron transfer from benzene derivatives reacts with the OH-adduct radicals to yield the corresponding phenol derivatives and DDQH2. DDQ is recovered by the reaction of DDQH2 with tert-butyl nitrite when DDQ acts as a photocatalyst for the hydroxylation of benzene derivatives by dioxygen.
Ohkubo, Kei,Hirose, Kensaku,Fukuzumi, Shunichi
supporting information
p. 2855 - 2861
(2015/02/05)