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Hitesh J Sanganee - One of the best experts on this subject based on the ideXlab platform.
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synthesis and utility of the 3 3 dimethyl 5 substituted 2 pyrrolidinone quat Chiral Auxiliary
Tetrahedron-asymmetry, 2002Co-Authors: Stephen G Davies, Gilles J M Doisneau, Jeremy C. Prodger, Darren J. Dixon, Hitesh J SanganeeAbstract:Abstract The synthesis and utility of the 3,3-dimethyl-5-substituted-2-pyrrolidinone ‘Quat’ Chiral Auxiliary in stereoselective enolate reactions of attached N -acyl side chains combined with the mild and non-racemising conditions required for the ultimate removal of the Chiral side chain is described.
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the superquat r 4 phenyl 5 5 dimethyl oxazolidin 2 one as an effective Chiral Auxiliary for conjugate additions asymmetric synthesis of aplysillamide b
Tetrahedron, 1999Co-Authors: Stephen G Davies, Hitesh J Sanganee, Peter SzolcsanyiAbstract:Abstract (R)-4-Phenyl-5,5-dimethyl-oxazolidin-2-one, readily available from d -phenylglycine, is shown to be an effective Chiral Auxiliary for stereoselective conjugate additions to attached α,β-unsaturated N-acyl moieties. Its utility is demonstrated by the asymmetric synthesis of the antifungal, antibacterial (−)-Aplysillamide B.
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asymmetric aldol and alkylation reactions mediated by the quat Chiral Auxiliary r 5 methyl 3 3 dimethyl 2 pyrrolidinone
Tetrahedron Letters, 1994Co-Authors: Stephen G Davies, Gilles J M Doisneau, Jeremy C. Prodger, Hitesh J SanganeeAbstract:Abstract Enolates derived from the N -propionoyl derivative of the “quat” Chiral Auxiliary ( R )-(−)-5-methyl-3,3-dimethyl-2-pyrrolidinone undergo highly stereoselective aldol and alkylation reactions. Removal of the Auxiliary has been demonstrated with LiOH, PhCH 2 OLi, MeOMgBr and LiAlH 4 to generate respectively (2 R ,3 R )-3-hydroxy-2-methyl-3-phenylpropionic acid in homoChiral form, and with 96% e.e. ( S )-2-methyl-3-phenylpropionic acid and derived methyl and benzyl esters and with >94% e.e. ( S )-2-methyl-3-phenylpropanol.
Junqi Nie - One of the best experts on this subject based on the ideXlab platform.
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diastereoselective alkylation reactions employing a new camphor based 2 phenylimino 2 oxazolidine Chiral Auxiliary
ChemInform, 2015Co-Authors: Longduo Zhang, Zuxing Chen, Guichun Yang, Junqi NieAbstract:A new camphor-based Chiral Auxiliary (I) is synthesized, which displays great potential for asymmetric alkylation reactions [ (V)].
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investigation of the diastereoselective mannich reaction using imidazolidin 2 thione as a Chiral Auxiliary
Tetrahedron-asymmetry, 2015Co-Authors: Liang Zhu, Zuxing Chen, Guichun Yang, Junqi NieAbstract:Abstracts Titanium mediated asymmetric Mannich reactions using imidazolidin-2-thione as a Chiral Auxiliary proceeded in good yields and with high diastereoselectivity to afford the anti -products in the presence of PPh 3 additive. A non-chelated transition state with the PPh 3 -bound titanium enolate was proposed to explain the stereochemistry of the product. Alcoholysis of the adducts with methanol cleaved the imidazolidin-2-thione Auxiliary to give the methyl esters in good yields and with excellent ee values.
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diastereoselective alkylation reactions employing a new camphor based 2 phenylimino 2 oxazolidine Chiral Auxiliary
Chinese Chemical Letters, 2014Co-Authors: Longduo Zhang, Zuxing Chen, Guichun Yang, Junqi NieAbstract:Abstract A new camphor-based 2-phenylimino-2-oxazolidine Chiral Auxiliary was prepared and it was shown to be a particularly effective Chiral Auxiliary for asymmetric alkylations affording high yields and diastereoselectivities. The alkylation products were readily cleaved by simple alkaline hydrolysis to give α -alkylated carboxylic acids in good yield and in almost enatiomerically pure form.
Guichun Yang - One of the best experts on this subject based on the ideXlab platform.
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diastereoselective alkylation reactions employing a new camphor based 2 phenylimino 2 oxazolidine Chiral Auxiliary
ChemInform, 2015Co-Authors: Longduo Zhang, Zuxing Chen, Guichun Yang, Junqi NieAbstract:A new camphor-based Chiral Auxiliary (I) is synthesized, which displays great potential for asymmetric alkylation reactions [ (V)].
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investigation of the diastereoselective mannich reaction using imidazolidin 2 thione as a Chiral Auxiliary
Tetrahedron-asymmetry, 2015Co-Authors: Liang Zhu, Zuxing Chen, Guichun Yang, Junqi NieAbstract:Abstracts Titanium mediated asymmetric Mannich reactions using imidazolidin-2-thione as a Chiral Auxiliary proceeded in good yields and with high diastereoselectivity to afford the anti -products in the presence of PPh 3 additive. A non-chelated transition state with the PPh 3 -bound titanium enolate was proposed to explain the stereochemistry of the product. Alcoholysis of the adducts with methanol cleaved the imidazolidin-2-thione Auxiliary to give the methyl esters in good yields and with excellent ee values.
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diastereoselective alkylation reactions employing a new camphor based 2 phenylimino 2 oxazolidine Chiral Auxiliary
Chinese Chemical Letters, 2014Co-Authors: Longduo Zhang, Zuxing Chen, Guichun Yang, Junqi NieAbstract:Abstract A new camphor-based 2-phenylimino-2-oxazolidine Chiral Auxiliary was prepared and it was shown to be a particularly effective Chiral Auxiliary for asymmetric alkylations affording high yields and diastereoselectivities. The alkylation products were readily cleaved by simple alkaline hydrolysis to give α -alkylated carboxylic acids in good yield and in almost enatiomerically pure form.
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boron enolates of a hydantoin Chiral Auxiliary derived from l phenylalanine a versatile tool for asymmetric aldol reactions
Tetrahedron-asymmetry, 2012Co-Authors: Jishu Zhang, Zuxing Chen, Guichun YangAbstract:Abstract The aldol reactions of boron enolates derived from a hydantoin Chiral Auxiliary derived from l -phenylalanine occur in good yields with high syn diastereoselectivity. Aldol adduct 4a is readily cleaved by hydrolysis to afford (2 S ,3 S )-3-hydroxy-2-methyl-3-phenylpropionic acid 5a in good yield and in almost enantiomerically pure form.
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stereoselective synthesis of an alarm pheromone of grematogaster ants using 4s 4 benzyloxazolidinone as Chiral Auxiliary
Chemistry of Natural Compounds, 2010Co-Authors: F Y Zhou, Zuxing Chen, Guichun YangAbstract:(S)-6-Methyl-3-octanone, a component of the alarm pheromone of Grematogaster ants, was synthesized through a key step of stereoselective Michael addition reaction using (4S)-4-benzyloxazolidinone as Chiral Auxiliary. The target product was obtained with an overall yield of 43.0% over six steps in high enantiomeric purity.
Alejandra G Suarez - One of the best experts on this subject based on the ideXlab platform.
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highly diastereoselective diels alder reaction using a Chiral Auxiliary derived from levoglucosenone
Organic Letters, 2006Co-Authors: Ariel M Sarotti, Rolando A Spanevello, Alejandra G SuarezAbstract:[reaction: see text] A new Chiral Auxiliary derived from levoglucosenone is reported. The compound is obtained by a cycloaddition reaction with 9-methoxy methylanthracene followed by a diastereoselective reduction of the C-2 keto function. The Auxiliary has been used as a Chiral template in an asymmetric Diels-Alder reaction of the corresponding acrylic ester derivative with cyclopentadiene. The results showed excellent diastereomeric excess even at room temperature when the reaction was promoted by Et(2)AlCl as the Lewis acid.
Stephen G Davies - One of the best experts on this subject based on the ideXlab platform.
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Direct asymmetric syntheses of Chiral aldehydes and ketones via N-acyl Chiral Auxiliary derivatives including Chiral Weinreb amide equivalents.
Chemical communications (Cambridge England), 2013Co-Authors: Stephen G Davies, Ai M. Fletcher, James E. ThomsonAbstract:This article covers N-acyl Chiral Auxiliary-based approaches to the asymmetric synthesis of enantiopure aldehydes and ketones. The use of diastereoisomerically pure N-acyl derivatives of Chiral auxiliaries (including Chiral Weinreb amide equivalents) and their conversion to the corresponding enantiopure aldehydes and ketones in a single synthetic operation by treatment with a hydride reducing agent or an organometallic reagent, respectively, are highlighted.
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the Chiral Auxiliary n 1 1 naphthyl ethyl o tert butylhydroxylamine a Chiral weinreb amide equivalent
Organic Letters, 2009Co-Authors: Alexander N Chernega, Stephen G Davies, Christopher J Goodwin, David Hepworth, Wataru Kurosawa, Paul M Roberts, James E. ThomsonAbstract:The Chiral Auxiliary N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxylamine is readily prepared from N-hydroxyphthalimide in four steps, with resolution giving access to both enantiomers in >98% ee, on a multigram (>25 g) scale. Conversion to a range of N-acyl derivatives, followed by highly diastereoselective alkylation (≥94% de) gives the corresponding Chiral, 2-substituted derivatives as single diastereoisomers (>98% de) after chromatography. Reductive cleavage with LiAlH4 allows direct access to Chiral aldehydes, and treatment with MeLi gives Chiral methyl ketones in excellent enantiopurity (≥94% ee). The Auxiliary can be recovered in >98% ee and recycled.
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synthesis and utility of the 3 3 dimethyl 5 substituted 2 pyrrolidinone quat Chiral Auxiliary
Tetrahedron-asymmetry, 2002Co-Authors: Stephen G Davies, Gilles J M Doisneau, Jeremy C. Prodger, Darren J. Dixon, Hitesh J SanganeeAbstract:Abstract The synthesis and utility of the 3,3-dimethyl-5-substituted-2-pyrrolidinone ‘Quat’ Chiral Auxiliary in stereoselective enolate reactions of attached N -acyl side chains combined with the mild and non-racemising conditions required for the ultimate removal of the Chiral side chain is described.
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the superquat r 4 phenyl 5 5 dimethyl oxazolidin 2 one as an effective Chiral Auxiliary for conjugate additions asymmetric synthesis of aplysillamide b
Tetrahedron, 1999Co-Authors: Stephen G Davies, Hitesh J Sanganee, Peter SzolcsanyiAbstract:Abstract (R)-4-Phenyl-5,5-dimethyl-oxazolidin-2-one, readily available from d -phenylglycine, is shown to be an effective Chiral Auxiliary for stereoselective conjugate additions to attached α,β-unsaturated N-acyl moieties. Its utility is demonstrated by the asymmetric synthesis of the antifungal, antibacterial (−)-Aplysillamide B.
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asymmetric aldol and alkylation reactions mediated by the quat Chiral Auxiliary r 5 methyl 3 3 dimethyl 2 pyrrolidinone
Tetrahedron Letters, 1994Co-Authors: Stephen G Davies, Gilles J M Doisneau, Jeremy C. Prodger, Hitesh J SanganeeAbstract:Abstract Enolates derived from the N -propionoyl derivative of the “quat” Chiral Auxiliary ( R )-(−)-5-methyl-3,3-dimethyl-2-pyrrolidinone undergo highly stereoselective aldol and alkylation reactions. Removal of the Auxiliary has been demonstrated with LiOH, PhCH 2 OLi, MeOMgBr and LiAlH 4 to generate respectively (2 R ,3 R )-3-hydroxy-2-methyl-3-phenylpropionic acid in homoChiral form, and with 96% e.e. ( S )-2-methyl-3-phenylpropionic acid and derived methyl and benzyl esters and with >94% e.e. ( S )-2-methyl-3-phenylpropanol.