- Diastereoselective conjugate addition of Grignard reagents to a homochiral fumaramide derived from Oppolzer's sultam
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Conjugate addition of Grignard reagents to N,N′-fumaroylbis[(2R)- bornane-10,2-sultam] 1 occurred with moderate to high levels of diastereoselectivity. Diastereomeric excesses were estimated by analysis of the 1H NMR spectra of the succinamide mixtures and enantiomeric excesses from 19F NMR spectra of the bis Mosher esters of the diols produced by reductive cleavage of the succinamides. Saponification of the succinamides gave the corresponding (R)-succinic acids with ees up to 92% showing that addition of the Grignard reagents takes place selectively on the re-face of 1.
- Reid, Gary P.,Brear, Kieron W.,Robins, David J.
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p. 793 - 801
(2007/10/03)
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- Enantioselective synthesis of 2-substituted 4-aminobutanoic acid (GABA) analogues via cyanomethylation of chiral enolates
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Cyanomethylation by bromoacetonitrile of sodium or lithium enolates derived from (4S,5R)-3-acyl-4-methyl-5-phenyl-1,3-oxazolidin-2-ones usually shows good stereoselecrivity; although the reaction of 3-(3-carboxypropanoyl)oxazolidinone 5d is exceptionally
- Azam, Shamim,D'Souza, Alice A.,Wyatt, Peter B.
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p. 621 - 627
(2007/10/03)
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- Asymmetric hydrogenation of prochiral carboxylic acids and functionalized carbonyl compounds catalysed by ruthenium(II)-binap complexes with aryl nitriles (binap=(R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl)
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Complexes RuCl2(ArCN)2(binap), II (binap=(R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl; ArCN=benzonitrile, a; 2-furancarbonitrile, b; pentafluorobenzonitrile, c) were prepared, and their solution properties were investigated by 31P NMR measurements.The catalytic aactivities and enantioselectivities for IIa-c catalysed hydrogenation of some prochiral acids were very similar to those provided by Ru2Cl4(binap)2(NEt3), I.In the hydrogenation of β-functionalized carbonyl compounds, however, IIa-c showed considerably lower activities and/or selectivities, compared with complex I.The differences in IIa-c catalysed reactions are discussed in relation to the coordinating abilities of ArCN in II.
- Shao, Liming,Takeuchi, Kasumi,Ikemoto, Makoto,Kawai, Toshiyasu,Ogasawara, Masamichi,et al.
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p. 133 - 147
(2007/10/02)
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- Asymmetric Synthesis of (R)- and (S)-4-(Substituted Benzyl)dihydrofuran-2(3H)-ones: An Application of the Ruthenium-binap Complex-catalysed Asymmetric Hydrogenation of Alkylidenesuccinic Acids
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A concise synthesis of (S)- or (R)-4-(substituted benzyl)dihydrofuran-2(3H)-ones (1) with high enantiomeric purity is presented. (S)- or (R)-(Substituted benzyl)succinic acids (6) 97percent enantiomeric excess) were first prepared by Ru2Cl4(R)- or (S
- Shao, Liming,Miyata, Shiro,Muramatsu, Hitoshi,Kawano, Hiroyuki,Ishii, Youichi,et al.
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p. 1441 - 1445
(2007/10/02)
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