- Highly Efficient Oxidative Cyanation of Aldehydes to Nitriles over Se,S,N-tri-Doped Hierarchically Porous Carbon Nanosheets
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Oxidative cyanation of aldehydes provides a promising strategy for the cyanide-free synthesis of organic nitriles. Design of robust and cost-effective catalysts is the key for this route. Herein, we designed a series of Se,S,N-tri-doped carbon nanosheets with a hierarchical porous structure (denoted as Se,S,N-CNs-x, x represents the pyrolysis temperature). It was found that the obtained Se,S,N-CNs-1000 was very selective and efficient for oxidative cyanation of various aldehydes including those containing other oxidizable groups into the corresponding nitriles using ammonia as the nitrogen resource below 100 °C. Detailed investigations revealed that the excellent performance of Se,S,N-CNs-1000 originated mainly from the graphitic-N species with lower electron density and synergistic effect between the Se, S, N, and C in the catalyst. Besides, the hierarchically porous structure could also promote the reaction. Notably, the unique feature of this metal-free catalyst is that it tolerated other oxidizable groups, and showed no activity on further reaction of the products, thereby resulting in high selectivity. As far as we know, this is the first work for the synthesis of nitriles via oxidative cyanation of aldehydes over heterogeneous metal-free catalysts.
- Hua, Manli,Song, Jinliang,Huang, Xin,Liu, Huizhen,Fan, Honglei,Wang, Weitao,He, Zhenhong,Liu, Zhaotie,Han, Buxing
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supporting information
p. 21479 - 21485
(2021/08/23)
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- One pot synthesis of aryl nitriles from aromatic aldehydes in a water environment
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In this study, we found a green method to obtain aryl nitriles from aromatic aldehyde in water. This simple process was modified from a conventional method. Compared with those approaches, we used water as the solvent instead of harmful chemical reagents. In this one-pot conversion, we got twenty-five aryl nitriles conveniently with pollution to the environment being minimized. Furthermore, we confirmed the reaction mechanism by capturing the intermediates, aldoximes.
- Chen, Qingqing,Han, Hongwei,Lin, Hongyan,Ma, Xiaopeng,Qi, Jinliang,Wang, Xiaoming,Yang, Yonghua,Zhou, Ziling
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p. 24232 - 24237
(2021/07/29)
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- Radical-anion coupling through reagent design: hydroxylation of aryl halides
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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.
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p. 14641 - 14646
(2021/11/17)
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- Method for hydrolyzing diarylether compound to generate aryl phenol compound
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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.
- -
-
Paragraph 0086-0089
(2021/09/29)
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- Transforming a Fluorochrome to an Efficient Photocatalyst for Oxidative Hydroxylation: A Supramolecular Dimerization Strategy Based on Host-Enhanced Charge Transfer
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The development of non-covalent synthetic strategy to fabricate efficient photocatalysts is of great importance in theranostic and organic materials. Herein, a fluorochrome N,N′-dimethyl 2,5-bis(4-pyridinium)thiazolo[5,4-d]thiazolediiodide (MPT) was transformed into an efficient photocatalyst through supramolecular dimerization in the cavity of cucurbit[8]uril (CB[8]). The host-enhanced charge transfer interaction within the supramolecular dimer 2MPT-CB[8] dramatically promoted intersystem crossing to produce triplet. In addition, the staggered conformation of 2MPT-CB[8] facilitated the energy transfer and electron transfer of the triplet. As a result, 2MPT-CB[8] could serve as a high-efficiency photocatalyst for the oxidative hydroxylation of arylboronic acids. This supramolecular dimerization strategy enriches the supramolecular engineering of functional π-systems. It is anticipated that this strategy can be extended to fabricate various π-systems with tailor-made functions.
- Tang, Bohan,Xu, Weiquan,Xu, Jiang-Fei,Zhang, Xi
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supporting information
p. 9384 - 9388
(2021/03/22)
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- Efficient solvent- And temperature-tuned access to aldoxime ethers and phenolic functions by Pd-catalyzed C-O cross-coupling of aldoximes with aryl bromides and bromo-chalcones
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A single method with a functionality switching option was developed for the first time for the Pd-catalyzed C-O cross-coupling of aryl bromides and bromo-chalcones with aldoximes. The ligand tBuXPhos (L2) was found to be an effective supporting ligand for the Pd-catalyzed coupling of aldoximes with bromo coupling partners. The functionality switching from oxime ethers to a phenolic or hydroxy group was driven by solvent or temperature. This method offers the products in good to excellent yields in short reaction times.
- Reeta,Rangarajan,Kaushik, Kumar,Singh, Rishi Pal,Singh, Manjula,Singh, Raj Pal
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supporting information
p. 1326 - 1336
(2020/02/11)
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- Palladium-Catalyzed Hydroxylation of Aryl Halides with Boric Acid
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Boric acid, B(OH)3, is proved to be an efficient hydroxide reagent in converting (hetero)aryl halides to the corresponding phenols with a Pd catalyst under mild conditions. Various phenol products were obtained in good to excellent yields. This transformation tolerates a broad range of functional groups and molecules, including base-sensitive substituents and complicated pharmaceutical (hetero)aryl halide molecules.
- Song, Zhi-Qiang,Wang, Dong-Hui
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supporting information
p. 8470 - 8474
(2020/11/18)
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- Dual aminoquinolate diarylboron and nickel catalysed metallaphotoredox platform for carbon-oxygen bond construction
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Herein, aminoquinolate diarylboron complexes are utilized as photocatalysts in dual Ni/photoredox catalyzed carbon-oxygen construction reactions. Via this unified metallaphotoredox platform, diverse (hetero)aryl halides can be conveniently coupled with acids, alcohols and water. This method features operational simplicity, broad substrate scope and good compatibility with functional groups. This journal is
- Day, Craig,Jia, Xin,Wei, Lanfeng,Xu, Liang,Zu, Weisai
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supporting information
p. 8273 - 8276
(2020/08/17)
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- Reductive cyanation of organic chlorides using CO2 and NH3 via Triphos–Ni(I) species
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Cyano-containing compounds constitute important pharmaceuticals, agrochemicals and organic materials. Traditional cyanation methods often rely on the use of toxic metal cyanides which have serious disposal, storage and transportation issues. Therefore, there is an increasing need to develop general and efficient catalytic methods for cyanide-free production of nitriles. Here we report the reductive cyanation of organic chlorides using CO2/NH3 as the electrophilic CN source. The use of tridentate phosphine ligand Triphos allows for the nickel-catalyzed cyanation of a broad array of aryl and aliphatic chlorides to produce the desired nitrile products in good yields, and with excellent functional group tolerance. Cheap and bench-stable urea was also shown as suitable CN source, suggesting promising application potential. Mechanistic studies imply that Triphos-Ni(I) species are responsible for the reductive C-C coupling approach involving isocyanate intermediates. This method expands the application potential of reductive cyanation in the synthesis of functionalized nitrile compounds under cyanide-free conditions, which is valuable for safe synthesis of (isotope-labeled) drugs.
- Dong, Yanan,Li, Yuehui,Yang, Peiju,Zhao, Shizhen
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- Trinuclear Mn2+/Zn2+based microporous coordination polymers as efficient catalysts foripso-hydroxylation of boronic acids
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Two microporous coordination polymers based on hourglass trinuclear building units, [Mn3(bpdc)3(bpy)]·2DMF and [Zn3(bpdc)3(bpy)]·2DMF·4H2O (bpdc = 4,4′-biphenyl dicarboxylic acid, bpy = 4,4′-bipyridine), have been synthesized under solvothermal conditions employing DMF as the solvent. Each structure consists of two crystallographically distinct M2+(M1 and M2) centers that are connectedviacarboxylate bridges from six bpdc ligands, generating a trinuclear metal cluster, [M3(bpdc)3(bpy)]. Cluster representation of the structure resulted in an interpenetrated net of rarehextopological type. Catalytic activities of the CPs have been assessed for the oxidative hydroxylation of phenylboronic acids (PBAs) using aqueous hydrogen peroxide (H2O2). Various substituted aryl/hetero-arylboronic acids RB(OH)2[R = phenyl, 2,4-difluorophenyl, 4-aminophenyl, 2-thiopheneetc.] underwentipso-hydroxylation smoothly at room temperature to generate the corresponding phenols in excellent yields. The main advantages of this protocol are the aqueous medium reaction, heterogeneous catalytic system, and short reaction time with excellent yield.
- Bora, Sanchay J.,Dutta, Anurag,Goswami, Shyam,Guha, Ankur K.,Paul, Rima,Thakur, Ashim J.
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p. 5454 - 5462
(2020/05/16)
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- Aerobic photooxidative hydroxylation of boronic acids catalyzed by anthraquinone-containing polymeric photosensitizer
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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
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p. 7927 - 7932
(2020/03/11)
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- Nickel-catalyzed oxidative hydroxylation of arylboronic acid: Ni(HBTC)BPY MOF as an efficient and ligand-free catalyst to access phenolic motifs
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A straightforward and mild oxidative ipso-hydroxylation of arylboronic acids has been achieved using a simple and non-noble metal, nickel-based reusable heterogeneous catalyst Ni(HBTC)BPY MOF (HBTC = benzene-1,3,5-tricarboxylate, BPY = 4,4′-bipyridine) in the presence of benign hydrogen peroxide as an oxidant under ambient reaction condition. The Ni(HBTC)BPY MOF exhibits excellent catalytic activity towards the formation of phenols from diverse arylboronic acids within short time and can be reused up to five times without any notable loss in its activity as well as shown high functional group tolerance even in the presence of sensitive functionalities and useful to achieve hydroxyl group in heterocycles.
- Latha, Ganesapandian,Devarajan, Nainamalai,Karthik, Murugan,Suresh, Palaniswamy
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- Copper nanoparticles supported on highly nitrogen-rich covalent organic polymers as heterogeneous catalysts for the ipso -hydroxylation of phenyl boronic acid to phenol
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This work describes a simple procedure for the synthesis of highly nitrogen-rich covalent organic polymers using commercially available starting materials like melamine and cyanuric chloride as a solid heterogeneous catalyst Cu/TCOP under solvothermal conditions. The structural properties of the as-synthesized solid heterogeneous catalyst were determined by X-ray diffraction (XRD), diffuse reflectance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), 13C-CP MAS nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. The catalytic activity of Cu/TCOP was investigated by focusing on the oxidation of phenylboronic acid under atmospheric conditions in an aqueous medium, achieving a very good yield up to 99%. The reaction performance was evaluated considering the effect of various parameters, such as the amount of the catalyst, reaction time, temperature, and the amount of the base and solvent. The Cu/TCOP catalyst is completely recoverable in a facile manner from the reaction mixture and the efficiency of the copper nanocatalyst can be recovered after five cycles.
- Sadhasivam, Velu,Harikrishnan, Muniyasamy,Elamathi, Ganesan,Balasaravanan, Rajendran,Murugesan, Sepperumal,Siva, Ayyanar
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supporting information
p. 6222 - 6231
(2020/05/13)
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- Photoinduced Hydroxylation of Organic Halides under Mild Conditions
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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
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supporting information
p. 8479 - 8484
(2019/10/16)
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- A practical method for preparation of phenols from arylboronic acids catalyzed by iodopovidone in aqueous medium
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A novel and efficient strategy for the ipso-hydroxylation of arylboronic acids to phenols has been developed using inexpensive, readily available, air-stable water-soluble povidone iodine as catalyst and aqueous hydrogen peroxide as oxidizing agent. The reactions were performed at room temperature under metal-, ligand- and base-free condition in a short reaction time. The corresponding substituted phenols were obtained in moderate to good yields by oxidative hydroxylation of arylboronic acids in aqueous medium.
- Dong, Bin,Ke, Yanxiong,Lu, Guangying,Ren, Jiangmeng,Ren, Yaoyao,Zeng, Bu-Bing,Zhou, Bin
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- Cellulose as recyclable organocatalyst for ipso-hydroxylation of arylboronic acids
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Cellulose catalyzed oxidative hydroxylation of aryl and hetero-arylboronic acids to the corresponding phenols under metal and base free strategy has been demonstrated. The sustainable ipso-hydroxylation takes place using hydrogen peroxide as an oxidant in water under mild condition in shorter period of time. Interestingly, easy recovery and reusability of heterogeneous catalyst without significant loss in catalytic yield makes the protocol environmentally benign.
- Laskar, Khairujjaman,Paul, Subham,Bora, Utpal
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- 3-Aryl-1,2,4-oxadiazole Derivatives Active Against Human Rhinovirus
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The human rhinovirus (hRV) is the causative agent of the common cold that often aggravates respiratory complications in patients with asthma or chronic obstructive pulmonary disease. The high rate of mutations and variety of serotypes are limiting the development of anti-hRV drugs, which emphasizes the need for the discovery of novel lead compounds. Previously, we identified antiviral compound 1 that we used here as the starting material for developing a novel compound series with high efficacy against hRV-A and -B. Improved metabolic stability was achieved by substituting an ester moiety with a 1,2,4-oxadiazole group. Specifically, compound 3k exhibited a high efficacy against hRV-B14, hRV-A21, and hRV-A71, with EC50 values of 66.0, 22.0, and 3.7 nM, respectively, and a relevant hepatic stability (59.6 and 40.7% compound remaining after 30 min in rat and human liver microsomes, respectively). An in vivo study demonstrated that 3k possessed a desirable pharmacokinetic profile with low systemic clearance (0.158 L·h-1·kg-1) and modest oral bioavailability (27.8%). Hence, 3k appears to be an interesting candidate for the development of antiviral lead compounds.
- Kim, Jinwoo,Shin, Jin Soo,Ahn, Sunjoo,Han, Soo Bong,Jung, Young-Sik
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p. 667 - 672
(2018/05/14)
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- Synthesis of Phenols: Organophotoredox/Nickel Dual Catalytic Hydroxylation of Aryl Halides with Water
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A highly effective hydroxylation reaction of aryl halides with water under synergistic organophotoredox and nickel catalysis is reported. The OH group of the resulting phenols originates from water, following deprotonation facilitated by an intramolecular base group on the ligand. Significantly, aryl bromides as well as less reactive aryl chlorides served as effective substrates to afford phenols with a wide range of functional groups. Without the need for a strong inorganic base or an expensive noble-metal catalyst, this process can be applied to the efficient preparation of diverse phenols and enables the hydroxylation of multifunctional pharmaceutically relevant aryl halides.
- Yang, Liu,Huang, Zhiyan,Li, Gang,Zhang, Wei,Cao, Rui,Wang, Chao,Xiao, Jianliang,Xue, Dong
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supporting information
p. 1968 - 1972
(2018/02/06)
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- C70 Fullerene-Catalyzed Metal-Free Photocatalytic ipso-Hydroxylation of Aryl Boronic Acids: Synthesis of Phenols
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A metal-free C70 fullerene-catalyzed method has been developed for the ipso-hydroxylation of aryl and heteroaryl boronic acids to corresponding phenols under photocatalytic conditions. The reaction proceeds under oxygen atmosphere and the mechanistic study revealed that C70 plays a critical role in the generation of reactive oxygen species in the presence of blue light. Reactions in the presence of 18O-labelled water and oxygen confirmed the generation of reactive oxygen species from oxygen molecule. Amine used as a reductant could be recovered in the form of imine. The current method is also applicable to the synthesis of aryl ethers in one-pot two-step process. (Figure presented.).
- Kumar, Inder,Sharma, Ritika,Kumar, Rakesh,Kumar, Rakesh,Sharma, Upendra
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supporting information
p. 2013 - 2019
(2018/04/02)
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- Size-tunable ZnO nanotapes as an efficient catalyst for oxidative chemoselective C–B bond cleavage of arylboronic acids
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Herein, we report a simple but effective chemical approach for the synthesis of size-tunable ZnO nanotapes by precipitation method in the presence of phytochemicals present in the flower extract of Lantana camara plant. The electron microscopic study confirmed that the size of ZnO nanotapes can be systematically controlled by varying the concentration of either flower extract or metal ions and the flower extract played the key role in controlling the growth of ZnO nanotapes. The phase and crystalline analysis was carried out by X-ray diffraction method which indicated that ZnO nanostructures are highly crystalline in nature and are free from any impurities. The synthesized ZnO nanostructures exhibited interesting optical properties as investigated by UV–vis absorption and photoluminescence spectroscopy. Further the surface functionalities affect the optical properties of ZnO nanostructures which possess relatively strong UV emissions; a blue emission and a green emission. The synthesized ZnO nanostructures showed excellent catalytic properties in the ipso-hydroxylation of different aryl/ hetero-arylboronic acid to phenol in a relatively greener reaction conditions. These catalysts are highly stable and are re-usable upto six cycles of ipso-hydroxylation without losing its catalytic properties.
- Phukan, Shreemoyee,Mahanta, Abhijit,Rashid, Md. Harunar
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- Cationic Polycarbazole Networks as Visible-Light Heterogeneous Photocatalysts for Oxidative Organic Transformations
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Photoredox catalysis has aroused great interest from chemists, as it offers a powerful tool for organic synthesis. Cationic polycarbazole networks (CPOP-28 and CPOP-29) were prepared via simple oxidative coupling reaction and applied as heterogeneous photocatalysts for a wide range of oxidative organic transformations, including oxidation of sulfides, hydroxylation of arylboronic acids, and cross-dehydrogenative coupling reactions, in the presence of visible light and air. Remarkably, photocatalytic activities are enhanced by ingenious introduction of trifluoromethyl groups to the polymeric network CPOP-29. The effects of the trifluoromethyl group on photocatalytic activities were elucidated in terms of photophysical and electrochemical properties. The appealing photocatalytic performance of the trifluoromethylated polymer is ascribed to superior light-absorption ability, longer fluorescence lifetime, and stronger oxidative capability. In addition, the photocatalysts showed good recyclability and could be reused after a simple separation workup.
- Liang, Hai-Peng,Chen, Qi,Han, Bao-Hang
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p. 5313 - 5322
(2018/05/14)
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- Synergistic Photo-Copper-Catalyzed Hydroxylation of (Hetero)aryl Halides with Molecular Oxygen
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Photoredox-mediated copper-catalyzed hydroxylation of (hetero)aryl halides (including chlorides, bromides, and iodides) with O2 at room temperature has been developed. Preliminary mechanistic studies indicate no arylcopper intermediate and that aryl radicals are involved in this procedure. 18O-labeling experiments confirm the hydroxyl oxygen atom originated from molecular oxygen.
- Zhang, Xin,Wu, Ge,Gao, Wenxia,Ding, Jinchang,Huang, Xiaobo,Liu, Miaochang,Wu, Huayue
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supporting information
p. 708 - 711
(2018/02/09)
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- Synthesis of Complex Phenols Enabled by a Rationally Designed Hydroxide Surrogate
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The conversion of aryl halides to phenols under mild reaction conditions is a longstanding and formidable challenge in organic chemistry. Herein, we report the rational design of a broadly applicable Pd-catalyzed method to prepare phenols with benzaldehyde oxime as a hydroxide surrogate. These reactions occur under mildly basic conditions and enable the late-stage hydroxylation of several functionally-dense drug-like aryl halides.
- Fier, Patrick S.,Maloney, Kevin M.
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supporting information
p. 4478 - 4482
(2017/04/13)
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- Reagent Design and Ligand Evolution for the Development of a Mild Copper-Catalyzed Hydroxylation Reaction
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Parallel synthesis and mass-directed purification of a modular ligand library, high-throughput experimentation, and rational ligand evolution have led to a novel copper catalyst for the synthesis of phenols with a traceless hydroxide surrogate. The mild reaction conditions reported here enable the late-stage synthesis of numerous complex, druglike phenols.
- Fier, Patrick S.,Maloney, Kevin M.
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supporting information
p. 3033 - 3036
(2017/06/07)
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- Photoinduced Vitamin B12-Catalysis for Deprotection of (Allyloxy)arenes
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Vitamin B12 is a natural cobalt complex that, while reduced to the "supernucleophilic" Co(I) form, can easily react with electrophiles via an SN2 mechanism. It is also shown to react via an SN2′ mechanism with allylic compounds allowing for photochemical deprotection of (allyloxy)arenes. A sustainable alternative to commonly used noble metal-catalyzed deprotection reactions is presented.
- Giedyk, Maciej,Turkowska, Joanna,Lepak, Sandra,Marculewicz, Marcin,ó Proinsias, Keith,Gryko, Dorota
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supporting information
p. 2670 - 2673
(2017/05/24)
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- N-Substituted 3(10H)-Acridones as Visible-Light, Water-Soluble Photocatalysts: Aerobic Oxidative Hydroxylation of Arylboronic Acids
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We disclosed a novel water-soluble photocatalyst that could promote aerobic oxidative hydroxylation of arylboronic acids to furnish phenols in excellent yields. This transformation uses visible-light irradiation under environmentally friendly conditions, that is, water-soluble catalyst, metal-free, green oxidant, room temperature.
- Xie, Hong-Yan,Han, Li-Shuai,Huang, Shan,Lei, Xiantao,Cheng, Yong,Zhao, Wenfeng,Sun, Hongbin,Wen, Xiaoan,Xu, Qing-Long
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p. 5236 - 5241
(2017/05/24)
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- Direct synthesis of nitriles from aldehydes with hydroxylamine-O-sulfonic acid in acidic water
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Herein is reported the selective transformation of aldehydes to nitriles in the presence of hydroxylamine-O-sulfonic acid (NH2OSO3H) as a source of the N atom and acidic water. The reaction works with high yields for a large array of aromatic and aliphatic aldehydes, as well as hindered aldehydes and conjugated aldehydes without purification. The reaction conditions are very mild and tolerate a wide array of functional groups. In principle, the reaction can be completed in vinegar.
- Quinn, Dylan J.,Haun, Graham J.,Moura-Letts, Gustavo
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supporting information
p. 3844 - 3847
(2016/08/02)
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- A dinuclear iron(II) complex bearing multidentate pyridinyl ligand: Synthesis, characterization and its catalysis on the hydroxylation of aromatic compounds
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A dinuclear iron(II) complex Fe2L2(μ2-Cl)2Cl2 (L = N,N-bis(pyridin-2-ylmethyl)prop-2-yn-1-amine) was prepared and fully characterized by UV–Vis spectroscopy, elemental analysis, electrochemical analysis and X-ray single crystal diffraction analysis. The catalytic activity of the complex was assessed for the hydroxylation of aromatic compounds by using aqueous H2O2 as an oxidant in acetonitrile. The catalytic system was applicable in a wide range of substrates including aromatic compounds with both electron-donating and electron-withdrawing substituents and showed moderate to good catalytic activity and selectivity in the oxidation reactions. Particularly, in the case of benzene the selectivity of phenol achieve to 74% with the reaction conversion of 24.8%.
- Gu, Erxing,Zhong, Wei,Ma, Hongxia,Xu, Beibei,Wang, Hailong,Liu, Xiaoming
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p. 159 - 165
(2018/03/29)
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- Grafting of Ru(III) complex onto nanosilica and its implication as heterogeneous catalyst for aerobic oxidative hydroxylation of arylboronic acids
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An ecofriendly and highly efficient protocol for aerobic oxidative hydroxylation of aryl and heteroaryl boronic acids catalyzed by Ru(III) imine complex immobilized on nanosilica, derived from rice husk, has been developed. The main significance of this protocol is the base free and aerobic reaction condition at room temperature, short reaction time, aqueous reaction medium, and excellent yield of the product. This heterogeneous catalyst is reusable up to sixth cycle without loss in activity.
- Gogoi, Nibedita,Gogoi, Pradip K.,Borah, Geetika,Bora, Utpal
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p. 4050 - 4052
(2016/08/18)
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- IPSO-hydroxylation of boronic acid via ozonolysis: A metal-, ligand-, and base-free method
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Here, we have developed a simple, efficient, and metal-, ligand-, and base-free method for the synthesis of functionalized aryl and alicyclic alcohols via ozonolysis of corresponding boronic acids in aqueous ethanol. The procedure is compatible with a variety of functional groups and can be utilized as an alternative method for the synthesis of hydroxy arenes and alicyclic alcohols.
- Bommegowda, Yadaganahalli K.,Mallesha, Ningegowda,Vinayaka, Ajjampura C.,Sadashiva, Maralinganadoddi P.
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supporting information
p. 268 - 270
(2016/05/02)
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- 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
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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
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supporting information
p. 2855 - 2861
(2015/02/05)
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- Direct hydroxylation of arenes with O2 catalyzed by V@CN catalyst
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A vanadium doped graphitic carbon nitride catalyst has been prepared and used for the direct hydroxylation of arenes with O2. Substituted arenes with electron-withdrawing groups such as CN, NO2, COOH, CF3, and COCH3 were oxygenated to the corresponding phenols in moderate yields. The catalyst also proved applicable for the hydroxylation of aromatic halides (F, Cl, and Br) with O2.
- Li, Yan,Li, Bing,Chen, Ting,Zhou, Zhicheng,Wang, Jun,Huang, Jun
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p. 1086 - 1092
(2015/07/01)
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- The Hydroxylation of Aromatics with Oxygen by Vanadium Catalysts Supported on N-doped Carbon Materials
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Vanadium catalysts supported on N-doped carbon materials (CN) were prepared and the catalyst VOSiW showed high activity for the hydroxylation of various aromatics with O2. Aromatics with electron-withdrawing groups such as CN, NO2, COOH, CF3, COCH3 and aromatic halides (F, Cl and Br) were oxygenated to the corresponding phenols in considerable yields. The CN materials were not only indispensable for the reusability of the vanadium catalyst VOSiW, but also favorable to the high catalytic activity. The VOSiW catalyst is ready for the hydroxylation of aromatics with O2 as both V4+ and V5+ species are coexisted in the VOSiW catalyst.
- Li, Yan,Li, Bing,Geng, Longfei,Wang, Jun,Wang, Yong,Huang, Jun
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p. 1014 - 1021
(2015/08/04)
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- Mild palladium-catalyzed cyanation of (hetero)aryl halides and triflates in aqueous media
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A mild, efficient, and low-temperature palladium-catalyzed cyanation of (hetero)aryl halides and triflates is reported. Previous palladium-catalyzed cyanations of (hetero)aryl halides have required higher temperatures to achieve good catalytic activity. This current reaction allows the cyanation of a general scope of (hetero)aryl halides and triflates at 2-5 mol % catalyst loadings with temperatures ranging from rt to 40 °C. This mild method was applied to the synthesis of lersivirine, a reverse transcriptase inhibitor.
- Cohen, Daniel T.,Buchwald, Stephen L.
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supporting information
p. 202 - 205
(2015/01/30)
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- Biosilica as an efficient heterogeneous catalyst for ipso-hydroxylation of arylboronic acids
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A mild and efficient protocol for the conversion of arylboronic acids to phenol via ipso-hydroxylation has been developed using aqueous hydrogen peroxide as oxidant and biosilica as heterogeneous catalyst. The recyclability of the catalyst is also evaluated and could be reused up to six consecutive cycles without a significant loss in catalytic activity.
- Mahanta, Abhijit,Adhikari, Pooja,Bora, Utpal,Thakur, Ashim Jyoti
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supporting information
p. 1780 - 1783
(2015/03/30)
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- Chitosan supported ionic liquid: A recyclable wet and dry catalyst for the direct conversion of aldehydes into nitriles and amides under mild conditions
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A green and highly efficient chitosan supported magnetic ionic liquid (CSMIL) was synthesized with chitosan (the most abundant biopolymer in nature and a cheap industrial waste product), methyl imidazole and anhydrous/hydrous FeCl3. The heterogeneous catalyst thus obtained was used for the direct conversion of aldehydes to the corresponding nitriles in the presence of NH2OH·HCl/dry-CSMIL/MeSO2Cl and amides with NH 2OH·HCl/wet-CSMIL/MeSO2Cl. A highlight of our approach is the easy separation of the catalyst from the reaction medium and thus the recyclability of the catalyst. This simple method can be applied to obtain a wide range of aromatic, heterocyclic, and aliphatic nitriles and amides.
- Khalafi-Nezhad, Ali,Mohammadi, Somayeh
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p. 13782 - 13787
(2014/04/17)
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- Reductive removal of methoxyacetyl protective group using sodium borohydride
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Herein, we have developed a mild and selective reductive deprotection method for the MAc protected alcohols using sodium borohydride. The new deprotection conditions provide a complete orthogonality between O-MAc and other protecting groups such as tert-butyl ester, N-Boc, Fmoc, Cbz, O-TBDMS, N-benzyl, O-benzyl, O-acetyl, N-acetyl, N-MAc, etc. In addition to O-MAc deprotection, this method is also applicable for S-MAc deprotection.
- Gadekar, Pradip K.,Hoermann, Maryann,Corbo, Faith,Sharma, Rajiv,Sarveswari,Roychowdhury, Abhijit
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p. 503 - 506
(2014/01/06)
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- Efficient method for demethylation of aryl methyl ether using aliquat-336
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A rapid method for selective cleavage of aryl methylethers can be achieved in the presence of a protic acid and a catalytic amount of phase-transfer catalyst (Aliquat-336). Aliquat-336 accelerates the rate of reaction and affords the corresponding phenols in excellent to good yields on a wide variety of substrates. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.]
- Waghmode, Suresh B.,Mahale, Ganesh,Patil, Viraj P.,Renalson, Kartik,Singh, Dharmendra
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supporting information
p. 3272 - 3280
(2013/10/01)
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- An unexpected involvement of ethyl-2-cyano-2-(hydroxyimino) acetate cleaved product in the promotion of the synthesis of nitriles from aldoximes: A mechanistic perception
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While attempting to synthesize nitriles from aldoximes using O-sulfonate esters of oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate], an unexpected involvement of oxyma cleaved product in promoting the synthesis of nitriles was observed. Such involvement of the oxyma cleaved product in the reaction mechanism, together with the usual anticipated pathway improved drastically the applicability of the method by reducing the time needed for the reaction to be completed over that of the sulfonyl chlorides. Other advantages of the present protocol are excellent yields in ambient and milder conditions.
- Dev, Dharm,Palakurthy, Nani Babu,Kumar, Nitesh,Mandal, Bhubaneswar
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supporting information
p. 4397 - 4400
(2013/07/26)
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- Direct preparation of nitriles from carboxylic acids in continuous flow
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A continuous-flow protocol for the preparation of organic nitriles from carboxylic acids has been developed. The method is based on the acid-nitrile exchange reaction with acetonitrile, used as the solvent, and takes place without any catalyst or additives under the high-temperature/high-pressure conditions employed. At 350 C and 65 bar, where acetonitrile is in its supercritical state, the transformation of benzoic acid to benzonitrile requires 25 min. The protocol has been tested for a variety of nitriles, including aromatic and aliphatic substrates.
- Cantillo, David,Kappe, C. Oliver
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p. 10567 - 10571
(2013/11/06)
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- Base-catalyzed dehydration of 3-substituted benzene cis -1,2-dihydrodiols: Stabilization of a cyclohexadienide anion intermediate by negative aromatic hyperconjugation
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Evidence that a 1,2-dihydroxycyclohexadienide anion is stabilized by aromatic "negative hyperconjugation" is described. It complements an earlier inference of "positive" hyperconjugative aromaticity for the cyclohexadienyl cation. The anion is a reactive intermediate in the dehydration of benzene cis-1,2-dihydrodiol to phenol. Rate constants for 3-substituted benzene cis-dihydrodiols are correlated by σ- values with = 3.2. Solvent isotope effects for the reactions are kH2O/kD 2O = 1.2-1.8. These measurements are consistent with reaction via a carbanion intermediate or a concerted reaction with a "carbanion-like" transition state. These and other experimental results confirm that the reaction proceeds by a stepwise mechanism, with a change in rate-determining step from proton transfer to the loss of hydroxide ion from the intermediate. Hydrogen isotope exchange accompanying dehydration of the parent benzene cis-1,2-dihydrodiol was not found, and thus, the proton transfer step is subject to internal return. A rate constant of ~1011 s-1, corresponding to rotational relaxation of the aqueous solvent, is assigned to loss of hydroxide ion from the intermediate. The rate constant for internal return therefore falls in the range 1011-1012 s -1. From these limiting values and the measured rate constant for hydroxide-catalyzed dehydration, a pKa of 30.8 ± 0.5 was determined for formation of the anion. Although loss of hydroxide ion is hugely exothermic, a concerted reaction is not enforced by the instability of the intermediate. Stabilization by negative hyperconjugation is proposed for 1,2-dihydroxycyclohexadienide and similar anions, and this proposal is supported by additional experimental evidence and by computational results, including evidence for a diatropic ("aromatic") ring current in 3,3-difluorocyclohexadienyl anion.
- Kudavalli, Jaya Satyanarayana,Rao, S. Nagaraja,More Oferrall, Rory A.,Bean, David E.,Fowler, Patrick W.,Sharma, Narain D.,Boyd, Derek R.,Kamerlin, Shina Caroline Lynn,Keeffe, James R.,Gronert, Scott
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supporting information
p. 14056 - 14069,14
(2020/08/31)
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- Efficient microwave-assisted Pd-catalyzed hydroxylation of aryl chlorides in the presence of carbonate
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An efficient microwave-assisted, palladium-catalyzed hydroxylation of aryl chlorides in the presence of a weak base carbonate was developed, which rapidly converts aryl and heteroaryl chlorides to phenols, and can be used when the aryl chloride is functionalized with a ketone, aldehyde, ester, nitrile, or amide.
- Yu, Chao-Wu,Chen, Grace S.,Huang, Chen-Wei,Chern, Ji-Wang
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supporting information; experimental part
p. 3688 - 3691
(2012/08/28)
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- Efficient and selective demethylation of heteroaryl methyl ethers in the presence of aryl methyl ethers
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A new and efficient method for the demethylation of 6-membered aza-heterocyclic methyl ethers is described using lithium chloride and para-toluenesulfonic acid. This process is chemoselective for aza-heterocyclic methyl ethers in the presence of aryl methyl ethers.
- Soni, Ajay,Dutt, Akhilesh,Sattigeri, Viswajanani,Cliffe, Ian A.
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experimental part
p. 1852 - 1857
(2011/06/20)
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- 2-(Trimethylsilyl)ethanol as a new alcohol equivalent for copper-catalyzed coupling of aryl iodides
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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
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p. 5338 - 5341
(2011/10/19)
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- Mechanisms of hydrolysis of phenyl- and benzyl 4-nitrophenyl-sulfamate esters
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The kinetics of hydrolysis at medium acid strength (pH interval 2-5) of a series of phenylsulfamate esters 1 have been studied and they have been found to react by an associative SN2(S) mechanism with water acting as a nucleophile attacking at sulfur, cleaving the S-O bond with simultaneous formation of a new S-O bond to the oxygen of a water molecule leading to sulfamic acid and phenol as products. In neutral to moderate alkaline solution (pH ≥ ~ 6-9) a dissociative (E1cB) route is followed that involves i) ionization of the amino group followed by ii) unimolecular expulsion of the leaving group from the ionized ester to give N-sulfonylamine [HNSO2] as an intermediate. In more alkaline solution further ionization of the conjugate base of the ester occurs to give a dianionic species which expels the aryloxide leaving group to yield the novel N-sulfonylamine anion [ -NSO2]; in a final step, rapid attack of hydroxide ion or a water molecule on it leads again to sulfamic acid. A series of substituted benzyl 4-nitrophenylsulfamate esters 4 were hydrolysed in the pH range 6.4-14, giving rise to a Hammett relationship whose reaction constant is shown to be consistent with the E1cB mechanism.
- Spillane, William J.,Thea, Sergio,Cevasco, Giorgio,Hynes, Michael J.,McCaw, Cheryl J. A.,Maguire, Neil P.
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supporting information; experimental part
p. 523 - 530
(2011/03/17)
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- Aromatic Hydroxylation at a Non-Heme Iron Center: Observed Intermediates and Insights into the Nature of the Active Species
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Mechanism of substrate oxidations with hydrogen peroxide in the presence of a highly reactive, biomimetic, iron aminopyridine complex, [Fe II(bpmen)(CH3CN)2][ClO4] 2 (1; bpmen=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2- diamine), is elucidated. Complex 1 has been shown to be an excellent catalyst for epoxidation and functional-group-directed aromatic hydroxylation using H2O2, although its mechanism of action remains largely unknown.1, 2 Efficient intermolecular hydroxylation of unfunctionalized benzene and substituted benzenes with H2O2 in the presence of 1 is found in the present work. Detailed mechanistic studies of the formation of iron(III)-phenolate products are reported. We have identified, generated in high yield, and experimentally characterized the key FeIII(OOH) intermediate (Imax=560 nm, rhombic EPR signal with g=2.21, 2.14, 1.96) formed by 1 and H2O2. Stopped-flow kinetic studies showed that FeIII(OOH) does not directly hydroxylate the aromatic rings, but undergoes rate-limiting self-decomposition producing transient reactive oxidant. The formation of the reactive species is facilitated by acid-assisted cleavage of the O-O bond in the iron-hydroperoxide intermediate. Acid-assisted benzene hydroxylation with 1 and a mechanistic probe, 2-Methyl-1-phenyl-2-propyl hydroperoxide (MPPH), correlates with O-O bond heterolysis. Independently generated FeIV=O species, which may originate from O-O bond homolysis in FeIII(OOH), proved to be inactive toward aromatic substrates. The reactive oxidant derived from 1 exchanges its oxygen atom with water and electrophilically attacks the aromatic ring (giving rise to an inverse H/D kinetic isotope effect of 0.8). These results have revealed a detailed experimental mechanistic picture of the oxidation reactions catalyzed by 1, based on direct characterization of the intermediates and products, and kinetic analysis of the individual reaction steps. Our detailed understanding of the mechanism of this reaction revealed both similarities and differences between synthetic and enzymatic aromatic hydroxylation reactions.
- Makhlynets, Olga V.,Rybak-Akimova, Elena V.
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supporting information; scheme or table
p. 13995 - 14006
(2011/04/12)
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- Practical, environment-benign and atom economic KOAc-catalysed deprotection of aryl TIPS ethers under mild fluoride-free conditions
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A KOAc-catalysed, fluoride-free protocol not only effects chemoselective deprotection of phenolic TIPS ethers without affecting acetal, ketal, carbamate, O-acetyl and aliphatic silyl ethers, but also improves its atom economy by recycling the silanol byproduct.
- Wang, Bing,Sun, Hui-Xia,Chen, Bo,Sun, Zhi-Hua
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supporting information; experimental part
p. 1112 - 1114
(2010/04/23)
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- Increasing the scope of palladium-catalyzed cyanations of aryl chlorides
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An improved protocol for the palladium-catalyzed cyanation of electron-rich aryl chlorides with potassium ferrocyanide [K4[Fe(CN)6]] is presented. Compared to previous procedures the substrate scope is significantly broadened.
- Schareina, Thomas,Jackstell, Ralf,Schulz, Thomas,Zapf, Alexander,Cotte, Alain,Gotta, Matthias,Beller, Matthias
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experimental part
p. 643 - 648
(2009/11/30)
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- Binding of HgCl2 by tripodal ligands controlled by AgPF 6: Receptors for the PF6- anion
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Mercuric chloride can readily enter into the biological cycle where it gets converted into other forms of mercury and causes severe neurotoxic, genotoxic and immunotoxic effects; a number of tripodal ligands have been synthesized that selectively bind mercuric chloride and in the presence of AgPF6, mercury can be removed and supramolecular complexes of the PF6 - anion are formed. The Royal Society of Chemistry.
- Singh, Ashutosh S.,Bharadwaj, Parimal K.
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p. 738 - 741
(2008/09/20)
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- Photocatalytic hydroxylation of aromatic ring by using water as an oxidant
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Electrophilic oxygen species photocatalytically derived from water molecules can selectively react with the aromatic ring of both benzene and its derivatives to produce the corresponding phenols and hydrogen over platinum-loaded titanium oxide when illuminated with light of appropriate wavelength in the absence of oxygen. The Royal Society of Chemistry.
- Yoshida, Hisao,Yuzawa, Hayato,Aoki, Masanori,Otake, Kazuko,Itoh, Hideaki,Hattori, Tadashi
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scheme or table
p. 4634 - 4636
(2009/03/11)
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