- Synthesis of the first water-soluble chiral tetrahydroxy diphosphine Rh(I) catalyst for enantioselective hydrogenation
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The synthesis of the first chiral polyhydroxy diphosphine-Rh(I) catalyst for asymmetric hydrogenation is described. Based on a simple synthetic pathway starting from D-mannitol the new metal complex is constructed. A special feature of the approach is the protection of the air-sensitive phosphinegroups by the catalytically active metal in the final synthetic steps. Therefore, tedious P-protection-deprotection procedures could be advantageously avoided. The new water-soluble catalyst hydrogenates functionalized olefins by up to 99.6% ee in water as solvent.
- Holz, Jens,Heller, Detlef,Stuermer, Rainer,Boerner, Armin
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- Divalent activation in temporary phosphate tethers: Highly selective cuprate displacement reactions
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(Chemical Equation Presented) Desymmetrization of a readily derived psuedo-C2-symmetric monocyclic phosphate via highly diastereoselective anti-SN2′ allylic displacement reactions is reported. This method utilizes of a wide variety o
- Whitehead, Alan,McParland, James P.,Hanson, Paul R.
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p. 5025 - 5028
(2007/10/03)
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- Production of optically active phospholanes
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Phospolanes and diphospholanes of the general formula I where: is H, C1-C6-aryl, alkylaryl, SiR32, R2is alkyl or aryl, A is H, C1-C6-alkyl, aryl, Cl or B is a linker with 1-5 C a
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- Asymmetric hydrogenation of β-keto esters
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Enantiomerically pure β-hydroxy esters are prepared by a process in which β-keto esters are reacted with hydrogen in the presence of catalysts of the formula LRuX2where X is halogen, acetate, allyl, methallyl, 2-phenylallyl, perchlorate, trifluoroacetate, tetrafluoroborate, hexafluoroantimonate, hexafluorophosphate, hexafluoroarsenate or trichloroacetate, L is a bidentate phospholane of the formula I ?where B=a bridging link with 1-5 carbon atoms between the two phosphorus atoms, R1=H, C1-C6-alkyl, aryl, alkylaryl or SiR23, R2=alkyl or aryl, m=0 or 1, R3=H or OR4, and R4=R1, with the proviso that if m=1 then R3=H and if m=0 then R3≠ H.
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Page column 6
(2008/06/13)
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- Synthesis of C2-symmetric analogues of 4-(pyrrolidino)pyridine: New chiral nucleophilic catalysts
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The syntheses of a series of enantiomerically pure C2-symmetric 4-(pyrrolidino)pyridine (PP Y) derivatives by SNAr of 4-halo-/4-phenoxypyridines and by cyclocondensation from 4-aminopyridine are described. Preliminary results pertaining to their use as catalysts for acylative kinetic resolution of 1-phenylethanol are also presented. A single-crystal X-ray analysis of PPY If is reported. The Royal Society of Chemistry 2000.
- Spivey, Alan C.,Maddaford, Adrian,Fekner, Tomasz,Redgrave, Alison J.,Frampton, Christopher S.
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p. 3460 - 3468
(2007/10/03)
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- Synthesis of Enantiomerically Pure (2R,5R) Disubstituted Pyrrolidines from D-Mannitol
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Pyrrolidines 1 and 2 are obtained from D-Mannitol, giving good total yields and in an enantiomerically pure form.Some comments and studies regarding pyrrolidine ring closure (key step) are also reported.
- Marzi, M.,Minetti, P.,Misiti, D.
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p. 10127 - 10132
(2007/10/02)
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- Improved syntheses of both enantiomers of 1,2,5,6-diepoxyhexane from (2S,5S)-1,2,5,6-hexanetetrol
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Several methods for the preparation of (2R,5R)- and (2S,5S)-1,2,5,6-diepoxyhexane (2) from 3,4-dideoxy-D-threo-hexitol [(2S,5S)-1,2,5,6-hexanetetrol (1)] as a single common chiral synthon are described. Among these methods, the methods via (2S,5S)-1,6-bis(pivaloyloxy)-2,5-hexanediol and (2S,5S)-2,5-bis(benzoyloxy)-1,6-dibromohexane, both derived from 1, provide the best results in terms of the selectivity, yield, and optical purity for the preparation of (R,R)-2 and (S,S)-2, respectively.
- Machinaga,Kibayashi
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p. 989 - 994
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF TRANS-(2R,5R)-BIS(BENZYLOXYMETHYL)PYRROLIDINE
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Trans-(2R,5R)-bis(benzyloxymethyl)-pyrrolidine (1) was prepared from 1,2:5,6-diisopropylidene mannitol.Key transformations included the selective protection of primary hydroxy groups and stereocontrolled cyclization.
- Marzi, M.,Misiti, D.
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p. 6075 - 6076
(2007/10/02)
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