Nonracemic Allylic Boronates through Enantiotopic-Group
... organic synthesis. In particular, α-chiral γ,γ-disubstituted allylic boronates are attractive reagents: not only can they be directly converted to chiral γ,γ-disubstituted allylic alcohols and amines by oxidation and amination, but they can also engage in carbonyl allylations that establish chiral a ...
... organic synthesis. In particular, α-chiral γ,γ-disubstituted allylic boronates are attractive reagents: not only can they be directly converted to chiral γ,γ-disubstituted allylic alcohols and amines by oxidation and amination, but they can also engage in carbonyl allylations that establish chiral a ...
CBS Reduction
... • In 1981 Itsuno et al reduced achiral ketones to chiral alcohols using alkoxy-amine-borane complexes in enantioselectivity and in high yield. • In 1987 E.J. Corey, with his co-workers, used oxazaborolidines to rapidlly reduce ketones in the presence of BH3-THF to give 2o alcohol in enantioselectivi ...
... • In 1981 Itsuno et al reduced achiral ketones to chiral alcohols using alkoxy-amine-borane complexes in enantioselectivity and in high yield. • In 1987 E.J. Corey, with his co-workers, used oxazaborolidines to rapidlly reduce ketones in the presence of BH3-THF to give 2o alcohol in enantioselectivi ...
Microsoft Word - Open Access Repository of Indian Theses
... components. Consequently a variety of approaches have been developed for their asymmetric and racemic synthesis. The chapter starts with the introduction and description of the various literature methods for the synthesis of various functionalized -butyrolactones. The approach towards the synthesis ...
... components. Consequently a variety of approaches have been developed for their asymmetric and racemic synthesis. The chapter starts with the introduction and description of the various literature methods for the synthesis of various functionalized -butyrolactones. The approach towards the synthesis ...
couverture these PRES Toulouse M ESCARCEGA 2011
... In 1980s, Schwartz pointed an expanded and better consideration for defining a catalysts as “homogeneous”, relating it to its possessing only a single type of active site and if having many active sites as “heterogeneous” catalysts.10 In particular, homogeneous asymmetric catalysis provides a powerf ...
... In 1980s, Schwartz pointed an expanded and better consideration for defining a catalysts as “homogeneous”, relating it to its possessing only a single type of active site and if having many active sites as “heterogeneous” catalysts.10 In particular, homogeneous asymmetric catalysis provides a powerf ...
Enantioselective Henry Reactions under Dual Lewis Acid/Amine
... selectivity (entry 1), whereas increasing the ligand loading above 45 mol % did not improve the result. The quantity of iPr2EtN was crucial too. Lower loading or absence of iPr2EtN (entries 3 and 4) led to diminished yields and ee values. Interestingly, the absence of iPr2EtN could be partially comp ...
... selectivity (entry 1), whereas increasing the ligand loading above 45 mol % did not improve the result. The quantity of iPr2EtN was crucial too. Lower loading or absence of iPr2EtN (entries 3 and 4) led to diminished yields and ee values. Interestingly, the absence of iPr2EtN could be partially comp ...
Carbohydrates Typical formula: C (H O) , eg glucose: C H O
... aldehydes, aldose, or ketones, ketose. By combination erythrose and threose are aldotetroses. ...
... aldehydes, aldose, or ketones, ketose. By combination erythrose and threose are aldotetroses. ...
Barton Deoxygenation
... Hydrogenation of Alkynes - Mechanism The trans alkene is formed because the vinyl carbanion intermediate that is formed is more stable when the larger R groups are further away from each other to avoid steric interactions. Protonation of this anion leads to the more stable trans adduct. Sodium meta ...
... Hydrogenation of Alkynes - Mechanism The trans alkene is formed because the vinyl carbanion intermediate that is formed is more stable when the larger R groups are further away from each other to avoid steric interactions. Protonation of this anion leads to the more stable trans adduct. Sodium meta ...
info
... i. NaBH4 will reduce an aldehyde, ketone, or acid chloride to the corresponding alcohol. It will not reduce an acid or an ester. ii. LiAlH4 will reduce an aldehyde, ketone, acid, or ester to the corresponding alcohol. iii. LiAlH(OtBu)3 will reduce an acid chloride to an aldehyde. iv. DIBAL will ...
... i. NaBH4 will reduce an aldehyde, ketone, or acid chloride to the corresponding alcohol. It will not reduce an acid or an ester. ii. LiAlH4 will reduce an aldehyde, ketone, acid, or ester to the corresponding alcohol. iii. LiAlH(OtBu)3 will reduce an acid chloride to an aldehyde. iv. DIBAL will ...
Heck Reactions
... sponge, TMEDA, DBU have been used. Silver and thallium salts shift the pathway to the cationic manifold; they often increase the rate of the reaction, lower reaction temperatures, minimize alkene isomerization, modify regioselectivity, and alter enantioselectivity. Halide salts (NaX, KX, LiX, TBAX, ...
... sponge, TMEDA, DBU have been used. Silver and thallium salts shift the pathway to the cationic manifold; they often increase the rate of the reaction, lower reaction temperatures, minimize alkene isomerization, modify regioselectivity, and alter enantioselectivity. Halide salts (NaX, KX, LiX, TBAX, ...
Exam 3 Answer Key
... 6. (2.5) True or False? A molecule with a non-superimposable mirror image must be chiral. 7. (2.5) True or False? A hydrogen attached to a carbon of a triple bond can be abstracted using a base, the conjugate acid of which is stronger than the alkyne. ...
... 6. (2.5) True or False? A molecule with a non-superimposable mirror image must be chiral. 7. (2.5) True or False? A hydrogen attached to a carbon of a triple bond can be abstracted using a base, the conjugate acid of which is stronger than the alkyne. ...
Catalytic, Enantioselective Alkylation of r
... Over the past several years, highly effective methods for enantioselective aldol additions catalyzed by Lewis acids have been developed.1 Analogous alkylations of imines, however, have not been nearly as well studied nor as successful.2 R-Imino esters are almost unstudied in Lewis acid-catalyzed rea ...
... Over the past several years, highly effective methods for enantioselective aldol additions catalyzed by Lewis acids have been developed.1 Analogous alkylations of imines, however, have not been nearly as well studied nor as successful.2 R-Imino esters are almost unstudied in Lewis acid-catalyzed rea ...
Organometallic Chemistry
... • Reactions of crotylmetal (2-butenylmetal) reagents with carbonyl substrates provide access to acyclic stereo- and enantioselective syntheses of β-methyl homoallylic alcohols. ...
... • Reactions of crotylmetal (2-butenylmetal) reagents with carbonyl substrates provide access to acyclic stereo- and enantioselective syntheses of β-methyl homoallylic alcohols. ...
Bifunctional Asymmetric Catalysis: Cooperative Lewis Acid/Base
... how to account for the increased yields observed for ScIII, AlIII, and ZnII when each is known to have slower ligand exchange rates. A plausible explanation is that the ligand exchange between the quinuclidine nitrogen and the imino ester must favor the bidentate binding afforded by the imino ester. ...
... how to account for the increased yields observed for ScIII, AlIII, and ZnII when each is known to have slower ligand exchange rates. A plausible explanation is that the ligand exchange between the quinuclidine nitrogen and the imino ester must favor the bidentate binding afforded by the imino ester. ...
nucleophilic addition on ketones and ketimines - ISI
... Another milestone in this area was published in the same year by the group of Yus who reported the first addition of dialkylzinc reagents to ketones promoted by a hydroxysulfonamide–titanium catalyst.3 This type of titanium-based catalyst was also already well-known for the asymmetric addition of dio ...
... Another milestone in this area was published in the same year by the group of Yus who reported the first addition of dialkylzinc reagents to ketones promoted by a hydroxysulfonamide–titanium catalyst.3 This type of titanium-based catalyst was also already well-known for the asymmetric addition of dio ...
ADVANCED SYNTHESIS Stereochemistry
... • If we use a free hydroxyl group then the peracid hydrogen bonds to the hydroxyl group • Results in a pseudo-intramolecular reaction • If alcohol is protected then epoxidation occurs from least hindered face OH ...
... • If we use a free hydroxyl group then the peracid hydrogen bonds to the hydroxyl group • Results in a pseudo-intramolecular reaction • If alcohol is protected then epoxidation occurs from least hindered face OH ...
Cooperative Lewis Acid/Base Systems
... to be the best cocatalyst across the board; ironically, indiumbased Lewis acids have infrequently been used in organic synthesis, and their coordination chemistry is not well-explored.17 One reason may be that InIII binds to many ligands reversibly and with comparatively low affinity.18 The most str ...
... to be the best cocatalyst across the board; ironically, indiumbased Lewis acids have infrequently been used in organic synthesis, and their coordination chemistry is not well-explored.17 One reason may be that InIII binds to many ligands reversibly and with comparatively low affinity.18 The most str ...
The first practical method for asymmetric epoxidation
... of both Ti(O-i-Pr)4 and diethyl tartrate sufficesI2under otherwise identical reaction conditions. However, for the less-reactive substrates in Table I (5a, 6a, and 7a), the “1-equiv” conditions described above were necessary to achieve reasonable reaction rates. Even under the “1-equiv” conditions, ...
... of both Ti(O-i-Pr)4 and diethyl tartrate sufficesI2under otherwise identical reaction conditions. However, for the less-reactive substrates in Table I (5a, 6a, and 7a), the “1-equiv” conditions described above were necessary to achieve reasonable reaction rates. Even under the “1-equiv” conditions, ...
A convenient method for the preparation of oxazaborolidine catalyst
... become an important area of research for pharmaceutical industries, as often two enantiomers of a chiral drug molecule display different biological activities.1 Asymmetric reduction of prochiral ketones is an extremely important methodology for the synthesis of chiral secondary alcohols. The oxazabor ...
... become an important area of research for pharmaceutical industries, as often two enantiomers of a chiral drug molecule display different biological activities.1 Asymmetric reduction of prochiral ketones is an extremely important methodology for the synthesis of chiral secondary alcohols. The oxazabor ...
Document
... • Dissolving metal reductions always form the more stable trans product preferentially. • The trans alkene is formed because the vinyl carbanion intermediate that is formed is more stable when the larger R groups are further away from each other to avoid steric interactions. Protonation of this anio ...
... • Dissolving metal reductions always form the more stable trans product preferentially. • The trans alkene is formed because the vinyl carbanion intermediate that is formed is more stable when the larger R groups are further away from each other to avoid steric interactions. Protonation of this anio ...
PART 3 Principles and Applications of Organometallics in Catalysis
... The effect of a catalyst is to change the rate of conversion of a substrate into products, but they do not change the position of an equilibrium. The thermodynamics of the reaction concerned have to be favourable at the outset; catalysts can't perform the miracle of pushing a reaction up the thermod ...
... The effect of a catalyst is to change the rate of conversion of a substrate into products, but they do not change the position of an equilibrium. The thermodynamics of the reaction concerned have to be favourable at the outset; catalysts can't perform the miracle of pushing a reaction up the thermod ...
Synthesis of Ligands for the Functionalization of Magnetic
... ligands attached to iron nanoparticles is the best choice for catalyzing the Mukaiyama-Aldol reaction. The synthesis of the ligand portion of the project has faced many problems. For instance, in step 1, the heating required is evaporating the small reaction solution, and NMR analysis has been showi ...
... ligands attached to iron nanoparticles is the best choice for catalyzing the Mukaiyama-Aldol reaction. The synthesis of the ligand portion of the project has faced many problems. For instance, in step 1, the heating required is evaporating the small reaction solution, and NMR analysis has been showi ...
Asymmetric hydrogenation
Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen preferentially to one of two faces of an unsaturated substrate molecule, such as an alkene or ketone. The selectivity derives from the manner that the substrate binds to the chiral catalysts. In jargon, this binding transmits spatial information (what chemists refer to as chirality) from the catalyst to the target, favoring the product as a single enantiomer. This enzyme-like selectivity is particularly applied to bioactive products such as pharmaceutical agents and agrochemicals.