- Controlled Reduction of Carboxamides to Alcohols or Amines by Zinc Hydrides
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New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH-ZnI2 system delivers alcohols and NaH-ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2)∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H?Zn?Cl)2 is the key species for the production of amines.
- Ong, Derek Yiren,Yen, Zhihao,Yoshii, Asami,Revillo Imbernon, Julia,Takita, Ryo,Chiba, Shunsuke
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supporting information
p. 4992 - 4997
(2019/03/13)
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- Chasing ChEs-MAO B Multi-Targeting 4-Aminomethyl-7-Benzyloxy-2H-Chromen-2-ones
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A series of 4-aminomethyl-7-benzyloxy-2H-chromen-2-ones was investigated with the aim of identifying multiple inhibitors of cholinesterases (acetyl- and butyryl-, AChE and BChE) and monoamine oxidase B (MAO B) as potential anti-Alzheimer molecules. Starting from a previously reported potent MAO B inhibitor (3), we studied single-point modifications at the benzyloxy or at the basic moiety. The in vitro screening highlighted triple-acting compounds (6, 8, 9, 16, 20) showing nanomolar and selective MAO B inhibition along with IC50 against ChEs at the low micromolar level. Enzyme kinetics analysis toward AChE and docking simulations on the target enzymes were run in order to get insight into the mechanism of action and plausible binding modes.
- Rullo, Mariagrazia,Catto, Marco,Carrieri, Antonio,de Candia, Modesto,Altomare, Cosimo Damiano,Pisani, Leonardo
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- Photochemical Cleavage of Benzylic C-O Bond Facilitated by an Ortho or Meta Amino Group
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The excited state meta effect, also known as the meta-ortho effect, results from selective electron transmission from an electron-donating group to the meta and ortho sites on an aromatic ring in its first excited singlet state. This effect facilitates photochemical cleavage of benzylic C-O or C-N bond to release the corresponding alcohol, carboxylic acid, or amine when an electron-donating amino group is at the meta position, as demonstrated in our recent work of using a 3-diethylaminobenzyl (DEABn) group as an effective photolabile protecting group (PPG). Herein, we demonstrate that an ortho amino group can also facilitate benzylic C-O bond cleavage to release an alcohol or carboxylic acid. However, an amino group at the meta position results in a PPG with better overall chemical and photochemical properties.
- Ding, Xiong,Wang, Pengfei
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p. 7309 - 7316
(2017/07/26)
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- Structurally Simple Benzylidene-Type Photolabile Diol Protecting Groups
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Two structurally simple photolabile protecting groups for releasing 1,2- and 1,3-diols have been developed. The diols can be protected in high yields and released from their corresponding acetals with high chemical efficiency.
- Ding, Xiong,Devalankar, Dattatray A.,Wang, Pengfei
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supporting information
p. 5396 - 5399
(2016/11/06)
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- Electrophilicity and nucleophilicity of commonly used aldehydes
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The present approach for determining the electrophilicity (E) and nucleophilicity (N) of aldehydes includes a kinetic study of KMNO4 oxidation and NaBH4 reduction of aldehydes. A transition state analysis of the KMNO4 promoted aldehyde oxidation reaction has been performed, which shows a very good correlation with experimental results. The validity of the experimental method has been tested using the experimental activation parameters of the two reactions. The utility of the present approach is further demonstrated by the theoretical versus experimental relationship, which provides easy access to E and N values for various aldehydes and offers an at-a-glance assessment of the chemical reactivity of aldehydes in various reactions. the Partner Organisations 2014.
- Pratihar, Sanjay
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p. 5781 - 5788
(2014/07/22)
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- Design, synthesis and evaluation of novel HDAC inhibitors as potential antitumor agents
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Phenyl imidazolidin-2-one was introduced as the linker for novel HDAC inhibitors. A focused library of 20 compounds was designed and synthesized, among which eight compounds showed equivalent or higher potencies against HDAC1 as compared to vorinostat. In vitro antitumor activity assays in HCT-116, PC-3 and HL-60 cancer cells revealed six compounds with potent antitumor activities, and compound 1o showed 6- to 9-fold higher potencies compared to vorinostat. In an HCT-116 nude mice xenograft model, compound 1o displayed significant antitumor activity in both continuous and intermittent dosing schedules.
- Cheng, Jianjun,Qin, Jihong,Guo, Sihua,Qiu, Hangdeng,Zhong, Yun
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p. 4768 - 4772
(2015/01/09)
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- Solvent-free reduction of carboxylic acids to alcohols with NaBH4 promoted by 2,4,6-trichloro-1,3,5-triazine and PPh3 in the presence of K2CO3
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A simple, rapid, and eco-friendly method for NaBH4 reduction of carboxylic acids to alcohols under solvent-free conditions was developed using a combination of 2,4,6-trichloro-1,3,5-triazine (TCT) with a catalytic amount of triphenylphosphine as an acid activator. With the 1 : 0.2 : 1.5 : 2 mole ratio of TCT : PPh3 : K2CO3 : NaBH4, carboxylic acids including aromatic acids, aliphatic acids, and N-protected α-amino acids (Fmoc, Z) could readily undergo reduction to give the corresponding alcohols in good to excellent yields within 10 min.
- Jaita, Subin,Kaewkum, Pantitra,Duangkamol, Chuthamat,Phakhodee, Wong,Pattarawarapan, Mookda
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p. 46947 - 46950
(2014/12/10)
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- Intriguing substituent effect in modified Hoveyda-Grubbs metathesis catalysts incorporating a chelating iodo-benzylidene ligand
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A series of modified Hoveyda-Grubbs catalysts incorporating a chelating iodo-benzylidene ligand were prepared and characterized. The presence of electron-withdrawing ring substituents in the para position to the iodide was found to decrease the catalytic activity, revealing that dissociation of the Ru...I-Ar bond is not the rate-determining step.
- Barbasiewicz, Michal,Blocki, Krzysztof,Malinska, Maura,Pawlowski, Robert
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supporting information
p. 355 - 358
(2013/02/22)
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- A new family of halogen-chelated hoveyda-grubbs-type metathesis catalysts
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Coordination, not insertion: New ruthenium benzylidenes with a chelating halogen atom were easily prepared and showed excellent stability and activity as metathesis catalysts (see figure). Structure-activity studies reveal that strength of the ruthenium-halogen interaction can be tuned across a wide range to set up a family of latent to active catalysts. Copyright
- Barbasiewicz, Michal,Michalak, Michal,Grela, Karol
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supporting information
p. 14237 - 14241,5
(2020/09/16)
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- Synthesis of photosynthesis-inhibiting nostoclide analogues
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A series of 34 3-benzyl-5-(arylmethylene)furan-2(5H)-ones, designed using the naturally occurring toxins nostoclides as a lead structure, was synthesized as potential inhibitors of the photosynthetic electron transport. All compounds were fully characterized by IR, NMR (1H and 13C), and MS spectrometry. HMBC and HSQC bidimensional experiments allowed 13C and 1H assignments. Their biological activities were evaluated in vitro as the ability to interfere with light-driven reduction of ferricyanide by isolated spinach chloroplasts. About two-thirds of the compounds exhibited inhibitory properties in the micromolar range against the basal electron flow from water to K3[Fe(CN)6]. The inhibitory potential of these 3-benzyl-5-(arylmethylene)furan-2(5H)-one lactones is higher than that of other nostoclide analogues previously synthesized in the same laboratories.
- Teixeira, Robson R.,Barbosa, Luiz C. A.,Forlani, Giuseppe,Pilo-Veloso, Dorila,Carneiro, Jose Walkimar De Mesquita
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experimental part
p. 2321 - 2329
(2009/12/29)
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- HYDROGENATION OF ESTERS WITH RU/BIDENTATE LIGANDS COMPLEXES
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The present invention relates to the field of catalytic hydrogenation and, more particularly, to the use of Ru complexes with bidentate ligands, having one amino or imino coordinating group and one phosphino coordinating group, in hydrogenation processes for the reduction of esters or lactones into the corresponding alcohol or diol respectively.
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Page/Page column 13
(2008/06/13)
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- HYDROGENATION OF ESTERS WITH RU/BIDENTATE LIGANDS COMPLEXES
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The present invention relates to the field of catalytic hydrogenation and, more particularly, to the use of Ru complexes with bidentate ligands, having one amino or imino coordinating group and one phosphino coordinating group, in hydrogenation processes for the reduction of esters or lactones into the corresponding alcohol or diol respectively.
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Page/Page column 26-29
(2008/06/13)
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- Fluorescence sensing based on cation-induced conformational switching: Copper-selective modulation of the photoinduced intramolecular charge transfer of a donor-acceptor biphenyl fluorophore
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The fluorescence emission energy of donor-acceptor substituted biphenyls is highly sensitive towards conformational changes of the interannular twist angle. By integrating 4-dimethylamino-4′-cyano-biphenyl into the ligand backbone of a thioether-rich metal receptor we designed a fluorescence sensor that exhibits high selectivity towards copper. Upon metal binding the ligand undergoes a significant conformational change, which induces a strong hypsochromic shift of the photoinduced charge-transfer emission. Steady-state absorption and fluorescence spectroscopy revealed a high affinity towards Cu(I) with a well-defined 1:1 metal-ligand complex stoichiometry. The nature of the conformational changes upon Cu(I) coordination were analyzed in detail by 1H NMR and 2D NOESY experiments. The spectroscopic data provide a coherent picture, which is consistent with a Boltzmann ground-state distribution of several rotamers that are locked into a more flattened geometry upon coordination of Cu(I).
- Cody, John,Fahrni, Christoph J.
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p. 11099 - 11107
(2007/10/03)
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- Controlled photochemical release of nitric oxide from O2-benzyl-substituted diazeniumdiolates
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An investigation of potential photosensitive protecting groups for diazeniumdiolates (R2N-N(O)=NO-) has been initiated, and here the effect of meta electron-donating groups on the photochemistry of O2-benzyl-substituted diazeniumdiolates (R2N-N(O)=NOCH2Ar) is reported. Photolysis of the parent benzyl derivative (Ar = Ph) results almost exclusively in undesired photochemistry-the formation of nitrosamine and an oxynitrene intermediate with very little, if any, photorelease of the diazeniumdiolate. We have been able to use meta substitution to tune the photochemistry of these benzylic systems. The desired diazeniumdiolate photorelease has been shown to become more substantial with stronger π-donating meta substituents. This effect has been verified by direct observation of the photoreleased diazeniumdiolate with 1H NMR spectroscopy and by NO quantification measurements conducted in high- and low-ph solutions. In addition, the observed rates of NO release are consistent with that expected for normal thermal decomposition of the diazeniumdiolate in aqueous solutions and also show the same pH dependence.
- Ruane, Patrick H.,Bushan, K. Mani,Pavlos, Christopher M.,D'Sa, Raechelle A.,Toscano, John P.
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p. 9806 - 9811
(2007/10/03)
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- Photochemically removable protecting groups based on covalently linked electron donor - Acceptor systems
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Photoremovable protecting groups based on intramolecular electron transfer have been synthesized and studied. One molecule contains a N,N-dimethylaniline chromophore covalently linked to a phenacyl ester of acetic acid. UV photolysis of this molecule results in the release of acetic acid. Laser flash photolysis experiments show that photolysis creates an intramolecular charge-transfer state that has a lifetime of approximately 500 ns. This charge-transfer state partitions between a bond scission pathway leading to elimination of acetic acid and a charge-recombination pathway leading back to ground-state reactants. An analogous system, using an anthracene chromophore, was also synthesized. This did not release the carboxylic acid upon UV pbotolysis. Instead, laser flash photolysis experiments showed rapid formation of an anthracene-localized triplet excited state.
- Lee, Kwangjoo,Falvey, Daniel E.
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p. 9361 - 9366
(2007/10/03)
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- Design, preparation, and electronic structure of high-spin cation diradicals derived from amine-based spin-polarized donors
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Amine-based donor radicals, such as dimethylamino-, diethylamino-and morpholinonitronyl nitroxides, were synthesized, and their donor abilities were examined by cyclic voltammetry. ESR spectra of the singly oxidized donor radicals showed ground state triplet signals derived from the cation radicals of these donor radicals. The result was interpreted by the presence of the ferromagnetic coupling between the generated π-spin and the localized unpaired electron on the radical unit. According to the molecular orbital calculations, the ferromagnetic coupling between these two spins is originated from the space-sharing nature between SOMO which is localized on the radical unit and SOMO' which is derived from HOMO of the donor radical upon one-electron oxidation. Therefore, the cation-radicals of these donor radicals can be regarded as a heteroanalogue of trimethylenemethane. p-and m-dimethylaminophenyl nitronyl nitroxides were synthesized in order to expand the π-electronic structure of the donor unit, and the singly oxidized species were also found to afford triplet ESR signals. The origin of the ferromagnetic coupling of these aminophenyl nitronyl nitroxides was discussed on the same basis. Charge transfer complexes of some of the donor radicals with chloranil or 2,3-dichloro5,6-dicyano-1,4-benzoquinone were prepared, and the conducting and magnetic properties were examined.
- Sakurai, Hiromi,Izuoka, Akira,Sugawara, Tadashi
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p. 9723 - 9734
(2007/10/03)
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