- Metal-free transfer hydrogenation catalysis by B(C6F 5)3
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The activation of amines by B(C6F5)3 is shown to effect the catalytic racemization of a chiral amine. Extending this strategy to a bimolecular process, catalytic transfer hydrogenation of imines, enamines, and N-heterocycles is demonstrated using iPr2NH as the source of hydrogen and a catalytic amount of the Lewis acid B(C 6F5)3.
- Farrell, Jeffrey M.,Heiden, Zachariah M.,Stephan, Douglas W.
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body text
p. 4497 - 4500
(2011/11/04)
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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 54
(2010/12/31)
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- Development of new HPLC chiral stationary phases based on native and derivatized cyclofructans
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An unusual class of chiral selectors, cyclofructans, is introduced for the first time as bonded chiral stationary phases. Compared to native cyclofructans (CFs), which have rather limited capabilities as chiral selectors, aliphatic-and aromatic-functionalized CF6s possess unique and very different enantiomeric selectivities. Indeed, they are shown to separate a very broad range of racemic compounds. In particular, aliphatic-derivatized CF6s with a low substitution degree baseline separate all tested chiral primary amines. It appears that partial derivatization on the CF6 molecule disrupts the molecular internal hydrogen bonding, thereby making the core of the molecule more accessible. In contrast, highly aromaticfunctionalized CF6 stationary phases lose most of the enantioselective capabilities toward primary amines, however they gain broad selectivity for most other types of analytes. This class of stationary phases also demonstrates high "loadability" and therefore has great potential for preparative separations. The variations in enantiomeric selectivity often can be correlated with distinct structural features of the selector. The separations occur predominantly in the presence of organic solvents.
- Sun, Ping,Wang, Chunlei,Breitbach, Zachary S.,Zhang, Ying,Armstrong, Daniel W.
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experimental part
p. 10215 - 10226
(2010/05/01)
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- Synthesis of α-methyl kainic acid by stereospecific lithiation-dearomatizing cyclization of a chiral benzamide
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Stereospecific lithiation of N-α-methylbenzyl benzamides gives configurationally stable tertiary benzyllithiums which undergo a stereospecific dearomatizing cyclization with >99% retention of stereochemistry. The products are partially saturated isoindolinones which carry a new fully-substituted stereogenic centre. A ten-step sequence converts one of these products to the α-methyl analogue of kainic acid.
- Clayden, Jonathan,Knowles, Faye E.,Menet, Christel J.
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p. 3397 - 3400
(2007/10/03)
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- Stereospecific Symthesis of N-(1-Phenylethyl)-2,4,5-triphenyloxazolidines
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Treatment of the diastereoisomeric N-(1-phenylethyl)-1,2-diphenyl-2-aminoethanols with benzaldehyde yields stereospecifically N-(1-phenylethyl)-2,4,5-triphenyloxazolidines with four chiral centers.The cofigurations of these oxazolidines are established th
- Alcaide, Benito,Lopez-Mardomingo, Carmen,Perez-Ossorio, Rafael,Plumet, Joaquin
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