- Synthesis of spirocyclic azacycles from the cyclization of furan tethered N-acyliminium ions
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The protic and Lewis acid promoted cyclization reactions of tethered furan-4,5-dihydroxypiperid-2-ones, furan-4,5-diacetoxypiperid-2-ones and furan-3,4-diacetoxypyrrolid-2-ones, via their corresponding N-acyliminium ion intermediates, have been studied. I
- Shengule, Sudhir R.,Willis, Anthony,Pyne, Stephen G.
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experimental part
p. 1207 - 1215
(2012/02/16)
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- Monoalkylation of acetonitrile by primary alcohols catalyzed by iridium complexes
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The monoalkylation of acetonitrile by primary alcohols was achieved in a one-pot sequence in the presence of iridium catalysts. A diversity of nitriles has been obtained from aryl- and alkyl-methanols in excellent yield.
- Anxionnat, Bruno,Gomez Pardo, Domingo,Ricci, Gino,Cossy, Janine
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supporting information; experimental part
p. 4084 - 4087
(2011/09/21)
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- C-H activation reactions of ruthenium N-heterocyclic carbene complexes: Application in a catalytic tandem reaction involving C-C bond formation from alcohols
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A series of ruthenium hydride N-alkyl heterocyclic carbene complexes has been investigated as catalysts for a tandem oxidation/Wittig/reduction reaction to give C-C bonds from alcohols. The C-H-activated carbene complex Ru(I iPr2Me2)′(PPh3) 2(CO)H (9) proves to be the most active precursor catalyzing the reaction of PhCH2OH and Ph3P=CHCN in 3 h at 70 °C. These results provide (a) a rare case in which N-alkyl carbenes afford higher catalytic activity than their N-aryl counterparts and (b) a novel example of the importance of NHC C-H activation in a catalytic cycle.
- Burling, Suzanne,Paine, Belinda M.,Nama, Devendrababu,Brown, Victoria S.,Mahon, Mary F.,Prior, Timothy J.,Pregosin, Paul S.,Whittlesey, Michael K.,Williams, Jonathan M. J.
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p. 1987 - 1995
(2007/10/03)
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- Borrowing hydrogen: Indirect "Wittig" olefination for the formation of C-C bonds from alcohols
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The successful development of an indirect three-step domino sequence for the formation of C-C bonds from alcohol substrates is described. An iridium-catalysed dehydrogenation of alcohol 1 affords the intermediate aldehyde 2. The desired C-C bond can then be formed by a facile Wittig olefination, yielding the intermediate alkene 3. In the final step the alkene is hydrogenated to afford the indirect Wittig product, the alkane 4. The key to this process is the concept of borrowing hydrogen; hydrogen removed in the initial dehydrogenation step is simply borrowed by the iridium catalyst. Functioning as a hydrogen reservoir, the catalyst facilitates C-C bond formation before subsequently returning the borrowed hydrogen in the final step. Herein we present full details of our examination into both the substrate and reaction scope and the limitations of the catalytic cycle. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Black, Phillip J.,Edwards, Michael G.,Williams, Jonathan M. J.
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p. 4367 - 4378
(2007/10/03)
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- A new alternative to Stryker's reagent in hydrosilylation: Synthesis, structure, and reactivity of a well-defined carbene-copper(II) acetate complex
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A new, air stable and well-defined carbene-copper(II) complex has been prepared, which is an efficient precatalyst for the 1,2- and 1,4-reduction of carbonyl compounds under hydrosilylation conditions. The Royal Society of Chemistry 2005.
- Yun, Jaesook,Kim, Daesung,Yun, Hoseop
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p. 5181 - 5183
(2007/10/03)
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- Highly efficient conjugate reduction of α,β-unsaturated nitriles catalyzed by copper/xanthene-type bisphosphine complexes
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α,β-Unsaturated nitriles are chemoselectively reduced to the corresponding saturated nitriles in high yields using a copper-DPEphos or Xantphos complex as catalyst in the presence of polymethylhydrosiloxane (PMHS) as the stoichiometric reducing agent and t-butanol as additive. The Royal Society of Chemistry 2005.
- Kim, Daesung,Park, Bu-Mahn,Yun, Jaesook
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p. 1755 - 1757
(2007/10/03)
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- Fluorescent ionophoric compounds with a cryptand/crown-ether portion and a coumarin portion, their preparation and their use for measuring metal cation concentrations
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A fluorescent ionophoric compound, comprising: a complexing moiety for selective binding of an ion; and a fluorescing moiety that contains close-lying n?*and ??* excited states, wherein the compound has a wavelength of maximum absorbance of at least about
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- Structure-based design of inhibitors of purine nucleoside phosphorylase. 1. 9-(Arylmethyl) derivatives of 9-deazaguanine
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Purine nucleoside phosphorylase (PNP, EC 2.4.2.1) is a salvage enzyme important to the T-cell-mediated part of the immune system and as such is an important therapeutic target. This paper describes the design, synthesis, and enzymatic evaluation of potent, competitive inhibitors of PNP. Potential inhibitors were designed using the three-dimensional structure of the enzyme in an iterative process that involved interactive computer graphics to model the native enzyme and complexes of it with the inhibitors, Monte Carlo-based conformational searching, and energy minimization. Studies of the enzyme/inhibitor complexes were used to determine priorities of the synthetic efforts. The resulting compounds were then evaluated by determination of their IC50 values and by X-ray diffraction analysis using difference Fourier maps. In this manner, we have developed a series of 9-(arylmethyl)- 9-deazapurines (2-amino-7-(arylmethyl)-4H-pyrrolo[3,2-d]-pyrimidin-4-ones) that are potent, membrane-permeable inhibitors of the enzyme. The IC50 values of these compounds range from 17 to 270 nM (in 1 mM phosphate), with 9-(3,4-dichlorobenzyl)-9-deazaguanine being the most potent inhibitor. X-ray analysis explained the role of the aryl groups and revealed the rearrangement of hydrogen bonds in the binding of the 9-deazaguanines in the active site of PNP relative to the binding of the 8-aminoguanines that results in more potent inhibition of the enzyme.
- Montgomery,Niwas,Rose,Secrist III,Babu,Bugg,Erion,Guida,Ealick
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