- SN2 Reactions in Hydrocarbon Solvents Using Ammonium-Terminated Polyisobutylene Oligomers as Phase-Solubilizing Agents and Catalysts
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Although SN2 reactions have been thoroughly studied in polar aprotic and protic solvents, not many studies have been done to study the rate of SN2 reaction in nonpolar solvents like alkanes due to the insolubility of anionic nucleophiles in these solvents. In this study, we investigated the use of N,N-diethyl-N-methylammonium-terminated polyisobutylene oligomers as phase-solubilizing agents for nucleophilic anions that could react with hydrocarbon-soluble substrates in alkanes. The results of these kinetic studies showed alkanes were comparable to MeCN as solvents in many reactions. Based on these studies, we developed a solid/liquid catalytic process using insoluble alkali metal carboxylate salts and a recyclable soluble polyisobutylene-bound catalyst that can be used to carry out SN2 reactions both in heptane and in hydrocarbon oligomeric solvents known as poly(α-olefins) (PAOs).
- Samunual, Peerada,Bergbreiter, David E.
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- Superfast and Water-Insensitive Polymerization on α-Amino Acid N-Carboxyanhydrides to Prepare Polypeptides Using Tetraalkylammonium Carboxylate as the Initiator
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We design the tetraalkylammonium carboxylate-initiated superfast polymerization on α-amino acid N-carboxyanhydrides (NCA) for efficient synthesis of polypeptides. Carboxylates, as a new class of initiator for NCA polymerization, can initiate the superfast NCA polymerization without the need of extra catalysts and the polymerization can be operated in open vessels at ambient condition without the use of glove box. Tetraalkylammonium carboxylate-initiated polymerization on NCA easily affords block copolymers with at least 15 blocks. Moreover, this method avoids tedious purification steps and enables direct polymerization on crude NCAs in aqueous environments to prepare polypeptides and one-pot synthesis of polypeptide nanoparticles. These advantages and the mild polymerization condition of tetraalkylammonium carboxylate-initiated NCA polymerization imply its great potential in functional exploration and application of polypeptides.
- Chen, Jiacheng,Chen, Kang,Ding, Yun,Ji, Zhemin,Liu, Longqiang,Liu, Runhui,Liu, Shiqi,Shao, Ning,Wu, Xue,Wu, Yueming,Zhang, Weiwei,Zhou, Min,Zhu, Minghui
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supporting information
p. 26063 - 26071
(2021/11/12)
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- Fluorescent Supramolecular Organic Frameworks Constructed by Amidinium-Carboxylate Salt Bridges
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We report here a set of fluorescent supramolecular organic frameworks (SOFs) that incorporate aggregation-induced emission (AIE) units within their frameworks. The fluorescent SOFs of this study were constructed by linking the tetraphenylethylene (TPE)-ba
- Jiang, Hongqin,Xie, Linhuang,Duan, Zhiming,Lin, Kunhua,He, Qing,Lynch, Vincent M.,Sessler, Jonathan L.,Wang, Hongyu
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supporting information
p. 15006 - 15012
(2021/09/25)
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- Lewis Acidity Scale of Diaryliodonium Ions toward Oxygen, Nitrogen, and Halogen Lewis Bases
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Equilibrium constants for the associations of 17 diaryliodonium salts Ar2I+X- with 11 different Lewis bases (halide ions, carboxylates, p-nitrophenolate, amines, and tris(p-anisyl)phosphine) have been investigated by titrations followed by photometric or conductometric methods as well as by isothermal titration calorimetry (ITC) in acetonitrile at 20 °C. The resulting set of equilibrium constants KI covers 6 orders of magnitude and can be expressed by the linear free-energy relationship lg KI = sI LAI + LBI, which characterizes iodonium ions by the Lewis acidity parameter LAI, as well as the iodonium-specific affinities of Lewis bases by the Lewis basicity parameter LBI and the susceptibility sI. Least squares minimization with the definition LAI = 0 for Ph2I+ and sI = 1.00 for the benzoate ion provides Lewis acidities LAI for 17 iodonium ions and Lewis basicities LBI and sI for 10 Lewis bases. The lack of a general correlation between the Lewis basicities LBI (with respect to Ar2I+) and LB (with respect to Ar2CH+) indicates that different factors control the thermodynamics of Lewis adduct formation for iodonium ions and carbenium ions. Analysis of temperature-dependent equilibrium measurements as well as ITC experiments reveal a large entropic contribution to the observed Gibbs reaction energies for the Lewis adduct formations from iodonium ions and Lewis bases originating from solvation effects. The kinetics of the benzoate transfer from the bis(4-dimethylamino)-substituted benzhydryl benzoate Ar2CH-OBz to the phenyl(perfluorophenyl)iodonium ion was found to follow a first-order rate law. The first-order rate constant kobs was not affected by the concentration of Ph(C6F5)I+ indicating that the benzoate release from Ar2CH-OBz proceeds via an unassisted SN1-type mechanism followed by interception of the released benzoate ions by Ph(C6F5)I+ ions.
- Legault, Claude Y.,Mayer, Robert J.,Mayr, Herbert,Ofial, Armin R.
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supporting information
(2020/03/13)
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- Development and Elucidation of a Pd-Based Cyclization–Oxygenation Sequence for Natural Product Synthesis
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Pd-catalyzed sequences involving oxidative addition, cyclization, and termination through intermolecular nucleophile capture have tremendous utility. Indeed, they can generate a plethora of different polycyclic structures possessing a diverse range of fun
- Yi, Heng,Hu, Pengfei,Snyder, Scott A.
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supporting information
p. 2674 - 2678
(2020/01/24)
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- Chiral recognition of carboxylate anions by (R)-BiNoL-based macrocyclic receptors
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Three (R)-BINOL-based macrocyclic receptors obtained via double-amidation reaction were used for chiral recognition of four anions derived from α-hydroxy and α-amino acids. The structural factors of hosts and guests that affect chiral recognition processes were also investigated, indicating that the proper geometry of both receptor and guest molecules plays a crucial role in effective enantio-discrimination.
- Tyszka-Gumkowska, Agata,Pikus, Grzegorz,Jurczak, Janusz
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supporting information
(2019/08/01)
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- Lanthanide Complexes Supported by a Trizinc Crown Ether as Catalysts for Alternating Copolymerization of Epoxide and CO2: Telomerization Controlled by Carboxylate Anions
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A new family of heterometallic catalysts based on trimetalated macrocyclic tris(salen) ligands and rare-earth metals was prepared and structurally characterized. The LaZn3 system containing anionic ligands such as acetate plays a critical role in catalyzing the alternating copolymerization of cyclohexene oxide (CHO) and CO2 with a high proportion of carbonate linkages. Among the lanthanide metals, the CeZn3 system exhibits high catalytic activity with a turnover frequency (TOF) of over 370 h?1. NMR analysis of the complex and end-group analysis of the polymer suggest that the acetate ligands are rapidly exchanged, not only among coordinated acetates, but also between coordinated acetates and added carboxylate anions. These unique properties make this the first example of telomerization for the copolymerization of CHO and CO2.
- Nagae, Haruki,Aoki, Ryota,Akutagawa, Shin-Nosuke,Kleemann, Julian,Tagawa, Risa,Schindler, Tobias,Choi, Gyeongshin,Spaniol, Thomas P.,Tsurugi, Hayato,Okuda, Jun,Mashima, Kazushi
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supporting information
p. 2492 - 2496
(2018/01/27)
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- Electrocatalytic Reduction of Dioxygen to Hydrogen Peroxide by a Molecular Manganese Complex with a Bipyridine-Containing Schiff Base Ligand
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The synthesis and electrocatalytic reduction of dioxygen by a molecular manganese(III) complex with a tetradentate dianionic bipyridine-based ligand is reported. Electrochemical characterization indicates a Nernstian dependence on the added proton source for the reduction of Mn(III) to Mn(II). The resultant species is competent for the reduction of dioxygen to H2O2 with 81 ± 4% Faradaic efficiency. Mechanistic studies suggest that the catalytically active species has been generated through the interaction of the added proton donor and the parent Mn complex, resulting in the protonation of a coordinated phenolate moiety following the single-electron reduction, generating a neutral species with a vacant coordination site at the metal center. As a consequence, the active catalyst has a pendent proton source in close proximity to the active site for subsequent intramolecular reactions.
- Hooe, Shelby L.,Rheingold, Arnold L.,MacHan, Charles W.
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supporting information
p. 3232 - 3241
(2018/03/13)
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- Synthesis, spectroscopic, and analyte-responsive behavior of a polymerizable naphthalimide-based carboxylate probe and molecularly imprinted polymers prepared thereof
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A naphthalimide-based fluorescent indicator monomer 1 for the integration into chromo- and fluorogenic molecularly imprinted polymers (MIPs) was synthesized and characterized. The monomer was equipped with a urea binding site to respond to carboxylate-containing guests with absorption and fluorescence changes, namely a bathochromic shift in absorption and fluorescence quenching. Detailed spectroscopic analyses of the title compound and various models revealed the signaling mechanism. Titration studies employing benzoate and Z-l-phenylalanine (Z-l-Phe) suggest that indicator monomers such as the title compound undergo a mixture of deprotonation and complex formation in the presence of benzoate but yield hydrogen-bonded complexes, which are desirable for the molecular imprinting process, with weakly basic guests like Z-l-Phe. Compound 1 could be successfully employed in the synthesis of monolithic and thin-film MIPs against Z-l-Phe, Z-l-glutamic acid, and penicillin G. Chromatographic assessment of the selectivity features of the monoliths revealed enantioselective discrimination and clear imprinting effects. Immobilized on glass coverslips, the thin-film MIPs of 1 displayed a clear signaling behavior with a pronounced enantioselective fluorescence quenching dependence and a promising discrimination against cross-analytes.
- Wagner, Ricarda,Wan, Wei,Biyikal, Mustafa,Benito-Pe?a, Elena,Moreno-Bondi, María Cruz,Lazraq, Issam,Rurack, Knut,Sellergren, B?rje
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p. 1377 - 1389
(2013/03/28)
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- Influence of the size and geometry of the anion binding pocket of sugar-urea anion receptors on chiral recognition
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Three new chiral urea-type anion receptors were synthesized from aromatic diamines and 1-amino-1-deoxyglucose. The anion binding properties of these receptors were studied using chiral carboxylates derived from mandelic acid and three α-amino acids. We found that the size of the anion binding pocket played an important role in chiral recognition processes. The best results were obtained for 1,8-diaminoanthracene and α-amino acid anions.
- Hamankiewicz, Paulina,Granda, Jaros?aw M.,Jurczak, Janusz
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p. 5608 - 5611
(2013/09/23)
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- Evaluation of the binding ability of tetraaza[2]arene[2]triazine receptors anchoring l-alanine units for aromatic carboxylate anions
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The binding affinities of three new tetraaza[2]arene[2]triazine based macrocycles anchoring one (AC1A) and two (AC2A and Me4AC2A) l-alanine amino acid units for five aromatic carboxylate anions (bz-, ph 2-, iph2-, tph2- and btc3-) were investigated in DMSO-d6. 1H NMR titrations revealed that the AC1A and AC2A receptors exhibit comparable anion affinities, suggesting that the two l-alanine binding units in AC2A are not simultaneously involved in the anion recognition as indicated by molecular dynamics simulations carried out for selected AC1A and AC2A associations using the AMBER force field (GAFF). New force field parameters were developed in order to mimic the structural singularity derived from the N-H macrocyclic bridges.
- Vicente, Ana I.,Caio, Jo?o M.,Sardinha, Jo?o,Moiteiro, Cristina,Delgado, Rita,Félix, Vítor
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experimental part
p. 670 - 680
(2012/02/13)
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- Meta-Substituted benzamide oligomers that complex mono-, di- and tricarboxylates: Folding-induced selectivity and chirality
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meta-Substituted arylamide trimer, pentamer and heptamer have been prepared from simple benzene-1,3-diamine, benzene-1,3-dicarboxylic acid, and 3-aminobenzoic acid units. 2D NOESY 1H NMR experiments reveal that these flexible oligomers form fol
- Shi, Zhu-Ming,Chen, Shi-Gui,Zhao, Xin,Jiang, Xi-Kui,Li, Zhan-Ting
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experimental part
p. 8122 - 8129
(2012/01/04)
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- POSITIVE RESIST COMPOSITION AND PATTERNING PROCESS
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A positive resist composition comprises (A) a resin component which becomes soluble in an alkaline developer under the action of an acid and (B) an acid generator. The resin (A) is a polymer comprising recurring units containing a non-leaving hydroxyl group represented by formula (1) wherein R1 is H, methyl or trifluoromethyl, X is a single bond or methylene, m is 1 or 2, and the hydroxyl group attaches to a secondary carbon atom. The composition is improved in resolution when processed by lithography.
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- Encapsulated binding sites - Synthetically simple receptors for the binding and transport of HCl
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We report a receptor with an encapsulated amine/amide binding site, which binds HCl with high affinity in organic media - the rate of HCl transport through an apolar phase is controlled by the degree of encapsulation of the HCl binding site.
- Winstanley, Keith J.,Allen, Sarah J.,Smith, David K.
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scheme or table
p. 4299 - 4301
(2011/03/19)
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- Direct observation of the ionization step in solvolysis reactions: Electrophilicity versus electrofugality of carbocations
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Rates and equilibria of the reactions of highly stabilized amino-substituted benzhydrylium ions (Ar2CH+) with carboxylate ions have been determined photometrically in acetone and acetonitrile solutions. Treatment of covalent benzhydryl carboxylates (Ar 2CH-O2CR) with aqueous acetone or acetonitrile leads to the regeneration of the colored amino-substituted benzhydrylium ions Ar 2CH+, which do not undergo subsequent reactions with the solvent. One can, therefore, directly measure the first step of SN1 reactions. The electrofugality order, i.e., the relative ionization rates of benzhydryl esters Ar2CH-O2CR with the same anionic leaving group, does not correlate with the corresponding electrophilicity order, i.e., the relative reactivities of the corresponding benzhydrylium ions Ar 2CH+ toward a common nucleophile. Thus, benzhydrylium ions which are produced with equal rates by ionization of the corresponding covalent esters may differ by more than 2 orders of magnitude in their reactivities toward nucleophiles, e.g., carboxylate ions. Variable intrinsic barriers account for the breakdown of the rate-equilibrium relationships. Complete free-energy profiles for the ionization of benzhydryl carboxylates Ar2CH-O 2CR are constructed, which demonstrate that the transition states of these ionizations are not carbocation-like. As a consequence, variation of the solvent-ionizing power Y has only a small effect on the ionization rate constant (m = 0.35 to 0.55) indicating that small values of m in the Winstein-Grunwald equation do not necessarily imply an SN2 type mechanism.
- Schaller, Heike F.,Tishkov, Alexander A.,Feng, Xinliang,Mayr, Herbert
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p. 3012 - 3022
(2008/09/20)
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- The chemistry of acylals. Part I. The reactivity of acylals towards Grignard and organolithium reagents
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Aldehyde acylals have been prepared and reacted with Grignard and alkyllithium reagents. Acylals from formaldehyde furnished complex reaction mixtures when reacted with both reagents. Acylals of other aldehydes gave reaction mixtures that consisted mainly of an ester, generated by replacing one of the carboxy groups with the organic part of the organometallic reagent, and regenerated aldehyde. The esters were formed in the highest yields. Yields above 90% were experienced when the acylals were reacted with Grignard reagents under Barbier conditions.
- Sydnes, Leiv K.,Sandberg, Marcel
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p. 12679 - 12690
(2007/10/03)
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- Process for the preparation of 1,3-dioxane derivatives useful in the preparation of HMG-COA reductase inhibitors
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A novel, overall process for the preparation of a compound of the formula I: STR1 where R1 and R2 are each independently hydrogen, an alkyl group, a cycloalkyl group, an aryl group or, taken together with the carbon atom to which they are attached, form a cycloalkyl group; and R3 is hydrogen, an alkyl group, or an aryl group, or salts thereof, useful as intermediates in the preparation of HMG-CoA reductase inhibitors; novel methods within the overall process; and novel intermediates produced by those methods.
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- Glycosylation using a one-electron-transfer, homogeneous reagent. Application to an efficient synthesis of the trimannosyl core of N-glycosylproteins
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Double glycosylation of methyl 2,4-di-O-benzyl-β-D-mannopyranoside with ethyl 2-O-benzoyl-3,4,6-tri-O-benzyl-1-thio-α-D-mannopyranoside using as promoter tris(4-bromophenyl)ammoniumyl hexachloroantimonate, a stable, commercial, and crystalline radical cat
- Zhang, Yong-Min,Mallet, Jean-Maurice,Sinay, Pierre
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