- Organocatalytic Deuteration Induced by the Dynamic Covalent Interaction of Imidazolium Cations with Ketones
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In this article, we suggest a new organocatalytic approach based on the dynamic covalent interaction of imidazolium cations with ketones. A reaction of N-alkyl imidazolium salts with acetone-d6 in the presence of oxygenated bases generates a dynamic organocatalytic system with a mixture of protonated carbene/ketone adducts acting as H/D exchange catalysts. The developed methodology of the pH-dependent deuteration showed high selectivity of labeling and good chiral functional group tolerance. Here we report a unique methodology for efficient metal-free deuteration, which enables labeling of various types of α-acidic compounds without trace metal contamination. (Figure presented.).
- Ananikov, Valentine P.,Galkin, Konstantin I.,Gordeev, Evgeniy G.
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supporting information
p. 1368 - 1378
(2021/01/18)
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- Manganese-Pincer-Catalyzed Nitrile Hydration, α-Deuteration, and α-Deuterated Amide Formation via Metal Ligand Cooperation
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A simple and efficient system for the hydration and α-deuteration of nitriles to form amides, α-deuterated nitriles, and α-deuterated amides catalyzed by a single pincer complex of the earth-abundant manganese capable of metal-ligand cooperation is reported. The reaction is selective and tolerates a wide range of functional groups, giving the corresponding amides in moderate to good yields. Changing the solvent from tert-butanol to toluene and using D2O results in formation of α-deuterated nitriles in high selectivity. Moreover, α-deuterated amides can be obtained in one step directly from nitriles and D2O in THF. Preliminary mechanistic studies suggest the transformations contributing toward activation of the nitriles via a metal-ligand cooperative pathway, generating the manganese ketimido and enamido pincer complexes as the key intermediates for further transformations.
- Ben-David, Yehoshoa,Diskin-Posner, Yael,Kar, Sayan,Milstein, David,Zhou, Quan-Quan,Zou, You-Quan
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p. 10239 - 10245
(2021/08/24)
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- Ruthenium-catalyzed selective α-deuteration of aliphatic nitriles using D2O
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Selective catalytic α-deuteration of aliphatic nitriles using deuterium oxide as a deuterium source is reported. A PNP-ruthenium pincer complex catalyzed the α-deuteration of aliphatic nitriles including acetonitrile. Efficient deuteration occurred with a low catalyst load (0.2 to 0.5 mol%) and under mild conditions. A [2+2] cycloadduct formation from nitrile functionality and a deprotonated catalytic intermediate, followed by an imine-enamine tautomerization and a H/D exchange between the enamine intermediate and deuterium oxide leading to the selective deuteration at the α-position of the nitrile, is proposed as a plausible reaction mechanism.
- Krishnakumar, Varadhan,Gunanathan, Chidambaram
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supporting information
p. 8705 - 8708
(2018/08/07)
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- The Ionic Hydrogen Bond and Ion Solvation. 7. Interaction Energies of Carbanions with Solvent Molecules
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The bonding energy of a water molecule to carbanions range from 11.0 kcal/mol for c-C5H5- to 13 - 15 kcal/mol for CH2CN-, CH2CHO-, and CH2COCH3- and to 16.2 kcal/mol for HCC-.Alcohols bond to c-C5H5- more strongly, by up to 20.6 kcal/mol for the strongly acidic CF3CH2OH, and the attachment energies show an inverse linear correlation with the acidities of the alcohols.The c-C5H5- ion exhibits unusual behavior in that it bonds to the hydrogen donor H2O more weakly (11.0 kcal/mol) than to CH3CN (15.5 kcal/mol).In contrast, the more localized pyrrolide ion c-C4H4N- bonds to the two solvents by comparable strength, 15.8 and 15.7 kcal/mol, respectively.These observations indicate a specific N-*OH hydrogen bonding contribution in c-C4H4N-*H2O, and/or an unusual C-*HC type hydrogen bonding contribution in c-C5H5-*CH3CN.As to structures, correlations between ΔHoD and ΔHoacid suggest that ligands may hydrogen bond to the ? system of c-C5H5-, and to the oxygen atoms in CH2CHO- and CH3COCH2-.The latter is supported by solvent shell effects in CH3COCH2-*nH2O.
- Meot-Ner (Mautner), Michael
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p. 3858 - 3862
(2007/10/02)
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- ON THE EXCHANGE OF CYANIDE WITH ACETONITRILE. A TEST OF THEORETICAL CALCULATIONS
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The theoretically predicted formation of an adduct between cyanide and anhydrous acetonitrile was tested experimentally; no evidence for such a complex was found.The previously reported radioactivity loss in the reactions of cyanide - 14C in acetonitrile solutions was possibly due to the protonation and loss of the hydrogen cyanide, since no exchange between cyanide and acetonitrile was evidenced within the sensitivity limits of 13C labelling.Potassium cyanide and carbonate in the presence of 18-crown-6 ether catalyze the H/D exchange between acetonitrile and trideuteroacetonitrile.
- Farcasiu, D.,Marino, G.,Rose, K. D.,Digenis, G. A.,Jay, M.
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p. 1487 - 1490
(2007/10/02)
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- Thermoneutral Isotope Exchange Reactions of Cations in the Gas Phase
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Rate constants have been measured for reactions of the type AD2+ + MH --> MD + ADH+, where AD2+ is CD3CND+, CD3CDOD+, (CD3COCD3)D+, or (C2D5)2OD+ and the MH molecules are alcohols, acids, mercaptanes, H2S, AsH3, PH3, or aromatic molecules.Rate constants are also presented for the reactions ArHD+ + D2O --> ArDD+ + HDO, where ArHD+ is a deuteronated aromatic molecule and ArDD+ is the same species with a D atom incorporated on the ring.In all but two cases, the competing deuteron transfer is sufficiently endothermic that it cannot be observed under the conditions of the ICR experiments at 320 - 420 K.The efficiencies of the isotope exchange reactions are interpreted in terms of estimated potential surface cross sections for the reactions AD2+ + MH --> 2+*MH> --> +> --> +*MD> --> ADH+ + MD.When the formation of the +> complex is estimated to be thermoneutral or slightly endothermic, the isotope exchange process is inefficient (probability of a reactive collision 2+*MH> --> +> is exothermic.For most of the systems, trends in reaction efficiency appear to be related to factors such as dipole moments of reactant species (or for aromatic compounds, the electron-donating or -withdrawing properties of ring substituents) which influence the relative orientation of the two reactant species in the complex.
- Ausloos, P.,Lias, S. G.
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p. 3641 - 3647
(2007/10/02)
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