- Electronic and Steric Optimization of Fluorogenic Probes for Biomolecular Imaging
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Fluorogenic probes are invaluable tools for spatiotemporal investigations within live cells. In common fluorogenic probes, the intrinsic fluorescence of a small-molecule fluorophore is masked by esterification until entry into a cell, where endogenous esterases catalyze the hydrolysis of the masking groups, generating fluorescence. The susceptibility of masking groups to spontaneous hydrolysis is a major limitation of these probes. Previous attempts to address this problem have incorporated auto-immolative linkers at the cost of atom economy and synthetic adversity. Here, we report on a linker-free strategy that employs adventitious electronic and steric interactions in easy-to-synthesize probes. We find that X···C = O n→π? interactions and acyl group size are optimized in 2′,7′-dichlorofluorescein diisobutyrate. This probe is relatively stable to spontaneous hydrolysis but is a highly reactive substrate for esterases both in vitro and in cellulo, yielding a bright, photostable fluorophore with utility in biomolecular imaging.
- Chyan, Wen,Kilgore, Henry R.,Gold, Brian,Raines, Ronald T.
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Read Online
- A Unified Approach to Decarboxylative Halogenation of (Hetero)aryl Carboxylic Acids
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Aryl halides are a fundamental motif in synthetic chemistry, playing a critical role in metal-mediated cross-coupling reactions and serving as important scaffolds in drug discovery. Although thermal decarboxylative functionalization of aryl carboxylic acids has been extensively explored, the scope of existing halodecarboxylation methods remains limited, and there currently exists no unified strategy that provides access to any type of aryl halide from an aryl carboxylic acid precursor. Herein, we report a general catalytic method for direct decarboxylative halogenation of (hetero)aryl carboxylic acids via ligand-to-metal charge transfer. This strategy accommodates an exceptionally broad scope of substrates. We leverage an aryl radical intermediate toward divergent functionalization pathways: (1) atom transfer to access bromo- or iodo(hetero)arenes or (2) radical capture by copper and subsequent reductive elimination to generate chloro- or fluoro(hetero)arenes. The proposed ligand-to-metal charge transfer mechanism is supported through an array of spectroscopic studies.
- Blakemore, David C.,Castellano, Felix N.,Chen, Tiffany Q.,Danilov, Evgeny O.,Dechert-Schmitt, Anne-Marie,Dow, Nathan W.,Fayad, Remi,Hauke, Cory E.,Knauber, Thomas,Macmillan, David W. C.,Pedersen, P. Scott,Rosko, Michael C.
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supporting information
(2022/05/20)
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- Method for promoting acylation of amine or alcohol by carbon dioxide
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The invention relates to a method for promoting acylation of amine or alcohol by carbon dioxide, which comprises the following steps of: mixing an amine compound, carboxylate or thiocarboxylate compound and a reaction solvent under the action of carbon dioxide, and reacting to obtain an amide compound, or under the action of carbon dioxide, mixing the alcohol compound, the thiocarboxylate compound and the reaction solvent [gamma]-valerolactone, and reacting to obtain the ester compound. According to the invention, under the promotion action of carbon dioxide, carboxylate or thiocarboxylate is used as an acylation reagent, and amine and alcohol are converted into amide and ester compounds in the absence of a transition metal catalyst, so that acylation reagents such as acyl chloride or anhydride with irritation and corrosivity are avoided; and the method has the advantages of simple operation, mild reaction conditions, high tolerance of substrate functional groups, strong applicability and high yield, and provides an efficient, reliable and economical preparation method for synthesis of amide and ester compounds.
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Paragraph 0034-0035
(2021/05/29)
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- Steric effect of NHC ligands in Pd(II)–NHC-catalyzed non-directed C–H acetoxylation of simple arenes
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Although there has been a lot of progress in oxidative arene C–H functionalization reactions catalyzed by Pd(II/IV) system, the non-directed, site-selective functionalization of arene molecules is still challenging. It has been established that ligands play a pivotal role in controlling rate- as well as selectivity-determining step in a catalytic cycle involving well-defined metal-ligand bonding. N-heterocyclic carbene (NHC) ligands have had a tremendous contribution in the recent extraordinary success of achieving high reactivity and excellent selectivity in many catalytic processes including cross-coupling and olefin-metathesis reactions. However, the immense potential of these NHC ligands in improving site-selectivity of non-directed catalytic C–H functionalization reactions of simple arenes is yet to be realized, where overriding the electronic bias on deciding selectivity is a burdensome task. The presented work demonstrated an initiative step in this regard. Herein, a series of well-defined discrete [Pd(NHCR′R)(py)I2] complexes with systematically varied degree of spatial congestion at the Pd centre, exerted through the R and R’ substituents on the NHC ligand, were explored in controlling the activity as well as the site-selectivity of non-directed acetoxylation of representative monosubstituted and disubstituted simple arenes (such as toluene, iodobenzene and bromobenzene, naphthalene and 1,2-dichlorobenzene). The resulting best yields were found to be 75% for toluene and 65% for bromobenzene with [Pd(NHCMePh)(py)I2], 75% for iodobenzene and 79% for naphthalene with [Pd(NHCMeMe)(py)I2], and 41% for 1,2-dichlorobenzene with [Pd(NHCCyCy)(py)I2]. Most importantly, with increasing the bulkiness of the NHC ligand in the complexes, the selectivity of the distal C-acetoxylated products in comparison to the proximal ones, was enhanced to a great extent in all cases. Considering the vast library of NHC ligands, this study underscores the future opportunity to develop more strategies to improve the activity and the crucial site-selectivity of C–H functionalization reactions in simple as well as complex organic molecules.
- Mandal, Tanmoy,Yadav, Sudha,Choudhury, Joyanta
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- Iridium-Catalyzed C(sp3)?H Addition of Methyl Ethers across Intramolecular Carbon–Carbon Double Bonds Giving 2,3-Dihydrobenzofurans
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Intramolecular addition of an O-methyl C(sp3)?H bond across a carbon-carbon double bond occurs in the iridium-catalyzed reaction of methyl 2-(propen-2-yl)phenyl ethers. The Ir/(S)-DTBM-SEGPHOS catalyst promotes the reaction efficiently in toluene at 110–135 °C to afford 3,3-dimethyl-2,3-dihydrobenzofurans. Enantioselective C(sp3)?H addition is achieved in the reaction of methyl 2-(1-siloxyethenyl)phenyl ethers, affording enantioenriched 3-hydroxy-2,3-dihydrobenzofuran derivatives with up to 96% ee. (Figure presented.).
- Ohmura, Toshimichi,Kusaka, Satoshi,Torigoe, Takeru,Suginome, Michinori
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supporting information
p. 4448 - 4453
(2019/09/16)
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- Ligand-Promoted Palladium-Catalyzed C?H Acetoxylation of Simple Arenes
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The palladium-catalyzed C?H oxidation of simple arenes is an attractive strategy to obtain phenols, which have many applications in the fine chemicals industry. Although some advances have been made in this research area, low reactivity and selectivity are, in general, observed. This report describes a new catalytic system for the efficient C?H acetoxylation of simple arenes based on Pd(OAc)2 and a pyridinecarboxylic acid ligand.
- Valderas, Carolina,Naksomboon, Kananat,Fernández-Ibá?ez, M. ángeles
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p. 3213 - 3217
(2016/10/24)
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- Synthesis of 8-Bromoflavone and Its Buchwald-Hartwig Reaction with Amines
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Simple and convenient synthesis of 8-bromoflavone was achieved, starting from 2-bromophenol through 3′-bromo-2′-hydroxyacetophenone whose preparation was managed to be solved by optimized Fries rearrangement. The Buchwald-Hartwig reaction of 8-bromoflavone with different type of primary and secondary amines was carried out.
- Pajtás, Dávid,Patonay, Tamás,Kónya, Krisztina
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supporting information
p. 97 - 102
(2015/12/26)
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- Silanediol-Catalyzed Chromenone Functionalization
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Promising levels of enantiocontrol are observed in the silanediol-catalyzed addition of silyl ketene acetals to benzopyrylium triflates. This rare example of enantioselective, intermolecular chromenone functionalization with carbonyl-containing nucleophiles has potential applications in the synthesis of bioactive chromanones and tetrahydroxanthones.
- Hardman-Baldwin, Andrea M.,Visco, Michael D.,Wieting, Joshua M.,Stern, Charlotte,Kondo, Shin-Ichi,Mattson, Anita E.
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supporting information
p. 3766 - 3769
(2016/08/16)
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- TETRAZOLINONE COMPOUND AND APPLICATIONS THEREOF
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Disclosed is a tetrazolinone compound having a high pest control effect and represented by the formula (1): wherein R1, R2, R3, and R11 each represent a halogen atom, a C1-C6 alkyl group, or the like; R4 and R5 each represent a hydrogen atom, a halogen atom, a C1-C3 alkyl group, or the like; R6 represents a C1-C3 alkyl group which may have a halogen atom(s) or the like; R7, R8, and R9 each represent a hydrogen atom, a halogen atom, or the like; R10 represents a C1-C3 alkyl group or the like; R12 represents a C1-C6 alkyl group, a C3-C6 cycloalkyl group, or the like, and R13 represents a C1-C6 alkyl group, a C2-C6 alkenyl group, or the like.
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Paragraph 0863; 0866
(2015/11/24)
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- Solventless acetylation of alcohols and phenols catalyzed by supported iron oxide nanoparticles
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Supported iron oxide nanoparticles on silicate catalysts were found to be efficient and easily recoverable materials in the acetylation of alcohols and phenols to their corresponding acetyl compounds using acetic anhydride under mild and solvent-less conditions. The supported iron oxide nanoparticles could be easily recovered from the reaction mixture and reused ten times without any loss in activity.
- Rajabi, Fatemeh,Luque, Rafael
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p. 129 - 132
(2014/01/06)
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- Bromination of phenols in bromoperoxidase-catalyzed oxidations
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Phenol and ortho-substituted derivatives furnish products of selective para-bromination, if treated with sodium bromide, hydrogen peroxide, and the vanadate(V)-dependent bromoperoxidase I from the brown alga Ascophyllum nodosum. Relative rates of bromination in morpholine-4-ethane sulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) increase by a factor 32, as the ortho-substituent in a phenol changes from F via Cl, OCH3, C(CH 3)3, and H to CH3. The polar effect in phenol bromination by the enzymatic method, according to a Hammett-correlation (ρ=-3), compares to reactivity of molecular bromine under identical conditions (ρ=-2). Hypobromous acid is not able to electrophilically substitute bromine for hydrogen at pH 6.2 in aqueous tert-butanol. The tribromide anion behaves in MES-buffered aqueous tert-butanol as electrophile (ρ~-3), showing a similar polar effect in phenol bromination as molecular bromine.
- Wischang, Diana,Hartung, Jens
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supporting information
p. 9456 - 9463
(2012/11/07)
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- Polyvinylpolypyrrolidone-bound boron trifluoride: A highly efficient catalyst for acylation of alcohols, phenols and trimethylsilyl ethers by acetic anhydride
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A highly efficient method for the acylation of alcohols, phenols and trimethylsilyl ethers with acetic anhydride is described using polyvinylpolypyrrolidone-bound boron trifluoride (PVPP-BF3) under mild and heterogeneous conditions at room temperature in good to excellent yields. The polyvinylpolypyrrolidone-boron trifluoride complex shows more water tolerant, non-corrosive and stable solid catalyst elevated Lewis acid properties.
- Mokhtary, Masoud,Qandalee, Mohammad,Najafizadeh, Faranak
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experimental part
p. 389 - 393
(2012/08/28)
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- Sonochemical synthesis of silica and silica sulfuric acid nanoparticles from rice husk ash: A new and recyclable catalyst for the acetylation of alcohols and phenols under heterogeneous conditions
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Silica nanoparticles were synthesized from rice husk ash at room temperature by sonochemical method. The feeding rate of percipiteting agent and time of sonication were investigated. The nanostructure of the synthesized powder was realized by the FE-SEM photomicrograph, FT-IR spectroscopy, XRD and XRF analyses. These analytical observations have revealed that the nano-sized amorphous silica particles are formed and they are spheroidal in shape. The average particle size of the silica powders is found to be around 50 nm. The as-synthesized silica nanoparticles were subsequently modified with chlorosulfonic acid and prepared silica sulfuric acid nanoparticles, which were employed as an efficient catalyst for the acylation of alcohols and phenols with acetic anhydride in excellent yields under solvent-free conditions at room temperature. This reported method is simple, mild, and environmentally viable and catalyst can be simply recovered and reused over 9 times without any significant loss of its catalytic activity.
- Salavati-Niasari, Masoud,Javidi, Jaber
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p. 705 - 712
(2013/02/22)
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- Remarkably high reactivity of Pd(OAc)2/pyridine catalysts: Nondirected C-H oxygenation of arenes
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Less is more: The rational optimization and general applicability of the catalytic system Pd(OAc)2/pyridine is described (see scheme). The catalyst shows excellent reactivity in the C-H oxygenation of simple aromatic substrates. The Pd/pyridine ratio is critical as the use of one equivalent of pyridine per Pd center leads to dramatic enhancements in both reactivity and site selectivity in comparison to Pd(OAc)2 alone.
- Emmert, Marion H.,Cook, Amanda K.,Xie, Yushu J.,Sanford, Melanie S.
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supporting information; experimental part
p. 9409 - 9412
(2011/11/07)
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- Iron-doped single-walled carbon nanotubes as new heterogeneous and highly efficient catalyst for acylation of alcohols, phenols, carboxylic acids and amines under solvent-free conditions
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Iron-doped single-walled carbon nanotubes (Fe/SWCNTs) represent an efficient and new heterogeneous reusable catalyst for the acylation of a variety of alcohols, phenols, carboxylic acids and amines with acid chlorides or acid anhydrides under solvent-free conditions. The reactions of various primary, secondary, tertiary, and benzylic alcohols, diols, phenols, as well as aromatic and aliphatic amines give acylated adducts in good to excellent yields.
- Sharghi, Hashem,Jokar, Mahboubeh,Doroodmand, Mohammad Mahdi
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experimental part
p. 426 - 442
(2011/04/15)
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- Platinum and palladium complexes containing cationic ligands as catalysts for arene H/D exchange and oxidation
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Cationic catalysts in HD: Palladium(II) and platinum(II) complexes of pyridinium-substituted bipyridine ligands are highly active and stable catalysts for H/D exchange and oxidation of aromatic C-H bonds (TONs up to 3200, TOFs up to 0.1 s-1; se
- Emmert, Marion H.,Gary, J. Brannon,Villalobos, Janette M.,Sanford, Melanie S.
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supporting information; experimental part
p. 5884 - 5886
(2010/11/19)
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- Efficient synthesis of 5-nitro-benzo[b]furans via 2-bromo-4-nitro-phenyl acetates
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Acetylation/Sonogashira cross-coupling reaction/cyclization has been carried out in one-pot using a Na2PdCl4/2-(di-tert-butylphosphino)-N-phenylindole/CuI system in TMEDA to give 5-nitro-2-substituted benzo[b]furans in excellent yields. We also describe the extension of this method to 4-EWG-2-bromo-phenols obtaining 2,5-disubstituted-benzo[b]furans in good yields.
- Bochicchio, Antonella,Chiummiento, Lucia,Funicello, Maria,Lopardo, Maria Teresa,Lupattelli, Paolo
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experimental part
p. 2824 - 2827
(2010/07/04)
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- A heterogeneous cobalt(II) Salen complex as an efficient and reusable catalyst for acetylation of alcohols and phenols
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Acetylation of various alcohols and phenols was performed successfully using an immobilized cobalt(II) catalyst in high yield. The catalyst shows high thermal stability and was also recovered and reused at least 10 times without any considerable loss of activity.
- Rajabi, Fatemeh
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scheme or table
p. 395 - 397
(2009/05/07)
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- Efficient method for oxidation of ketones to esters with 4-aminoperoxybenzoic acid supported on silica gel
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4-Aminoperoxybenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of ketones to esters. Copyright Taylor & Francis Group, LLC.
- Ghazanfari, Dadkhoda,Hashemi, Mohammed M.,Shahidi-Zandi, Mehdi
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p. 2037 - 2042
(2008/09/21)
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- Effect of cyclodextrins on electrophilic aromatic bromination in aqueous solution
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Cyclodextrins act as molecular reactors to change the ratios of the products of reactions of anisole, acetanilide, 3-methylanisole, and 3-methylacetanilide with pyridinium dichlorobromate. With anisole and acetanilide, bromination at the para position is favoured over ortho substitution, and the effect is greatest with α-cyclodextrin. In the reactions of the methylanisole and methylacetanilide, the cyclodextrins afford higher yields of monobrominated products and less of the di- and tribromides, and β-cyclodextrin has the greatest effect. These outcomes can be attributed to inclusion of the substrates within the cyclodextrins restricting access of the reagent adjacent to the methoxy and acetamido groups. The yields of 4-bromoanisole, 4-bromoacetanilide, 4-bromo-3-methylanisole, and 4-bromo-3-methylacetanilide are thus increased from 73 to 94, 55 to 98, 37 to 86, and 39 to 72%, respectively. Perhaps more significantly, the quantities of the corresponding by-products are substantially reduced, from 27 to 6, 45 to 2, 63 to 14, and 61 to 28%. Since the reactions occur readily in water at ambient temperature, the cyclodextrins make them very efficient.
- Dumanski, Paul G.,Easton, Christopher J.,Lincoln, Stephen F.,Simpson, Jamie S.
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p. 1107 - 1111
(2007/10/03)
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- An efficient chemo and regioselective oxidative nuclear bromination of activated aromatic compounds using lithium bromide and ceric ammonium nitrate
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A mild, efficient and highly chemo- and regioselective method for the bromination of electron rich aromatic molecules has been developed by electrophilic substitution of Br+, which was generated in situ from LiBr using ceric ammonium nitrate as the oxidant. Free aromatic amines remained unaffected under the reaction conditions.
- Roy, Subhas Chandra,Guin, Chandrani,Rana, Kalyan Kumar,Maiti, Gourhari
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p. 6941 - 6942
(2007/10/03)
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