Anti-aldol Reaction Research Articles

Highly Diastereoselective Boron-Mediated anti-Aldol Reactions of 4-Silyl Substituted 2,2-Dimethyl-1,3-dioxan-5-one. Diastereo- and Enantioselective Synthesis of Protected Oxopolyols

The boron enolate of 4-silylated 2,2-dimethyl-1,3-dioxan-5-one (S)-3 reacts with representative aldehydes in a highly anti diastereoselective aldol reaction to give the corresponding adducts (S,S,S)-4 in 78-93% yield with diastereoisomeric excesses of de = 96-98%. The removal of the silyl group via the triethylamine-trihydrofluoride complex leads to protected oxopolyols (S,S)-5 in good yields (64-79%) with excellent diastereomeric and enantiomeric excesses (de,ee = 96-98%). The absolute configuration was determined by X-ray structure analysis of (S,S)-5c.

Kinetic resolution in asymmetric anti aldol reactions of branched and straight chain racemic 2-phenylsulfanyl aldehydes: asymmetric synthesis of cyclic ethers and lactones by phenylsulfanyl migration

The kinetic resolution of branched and straight chain 2-phenylsulfanyl aldehydes by the Lewis acid-catalysed asymmetric anti aldol reaction followed by reduction to single enantiomers of 1,3-diols and/or acid-catalysed cyclisation with PhS migration provides a route to enantiomerically pure cyclic ethers and lactones with full stereochemical control.

ChemInform Abstract: anti Aldol Reactions of Lactate‐Derived Ketones: Application to the Total Synthesis of (‐)‐ACRL Toxin IIIB.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Anti aldol reactions of lactate-derived ketones: Application to the total synthesis of (-)-ACRL toxin IIIB

The fungal polyketide derivative (-)-ACRL toxin IIIB ( 4) has been prepared in 15 steps (21 % yield) from ketone ( S)- 7 with 88% overall ds. The boron-mediated anti aldol reaction of ( S)- 7 is used twice in the synthesis, controlling the stereochemistry at C 8 / C 9 and C 12 / C 13.

Studies in polypropionate synthesis: High π-face selectivity in syn and anti aldol reactions of chiral boron enolates of lactate-derived ketones

Use of c Hex 2BCl / Me 2NEt in the aldol reactions of the α′-benzoyloxy ketone 7 with aldehydes leads to high stereoselectivity (97–99.5% ds) for the crystalline anti adducts 11. Under similar conditions, the corresponding benzyl ether 6 favours formation of the syn adducts 9.

High π-face selectivity in anti aldol reactions of E-enol borinates from chiral alkoxymethyl ketones: stereocontrolled synthesis of a C24-C32 polyol subunit of rapamycin

Using (c-C 6 H 11 ) 2 BCl/Et 3 N, the aldol reactions of the α-chiral alkoxymethyl ketones 5 and 6 with achiral aldehydes given the 1,2-anti-2,4-anti adducts 7 and 8 in 83-95% yield with ≥95% diastreoselectivity. This novel aldol reaction was applied to a concise and highly stereocontrolled synthesis of the C 24 -C 32 subunit 9 of rapamycin (10)

ChemInform Abstract: Kinetic Resolutions in Anti Aldol Reactions: Asymmetric Synthesis of Heterocycles with Phenylthio Migration

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: The Rational Design of Highly Stereoselective Boron Enolates Using Transition‐State Computer Modeling: A Novel, Asymmetric Anti Aldol Reaction for Ketones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Kinetic Resolutions in Anti Aldol Reactions: Asymmetric Synthesis of Heterocycles with Phenylthio Migration

Abstract Kinetic resolutions in Lewis acid catalysed asymmetric anti aldol reactions of the boron enolate of imide (2) with racemic 2-phenylthio aldehydes (3) give good yields of Felkin anti, anti aldols (6). The synthesis of homochiral cyclic ethers (4) and a simple novel route to homochiral lactones (5) are described.

The rational design of highly stereoselective boron enolates using transition-state computer modeling: a novel, asymmetric anti aldol reaction for ketones

The design and development of highly enantioselective anti aldol reactions based on computer-aided transition-state modeling is reported. The new chiral boron ligand L=6 was conceived based on its conformational preferences and on minimization of (±) double gauche pentane interactions. Modeling the transition structures for the aldol reaction of Z enolates 1 (L=6) predicted a selectivity which is equal to or slightly lower than that calculated and experimentally tested with L=Ipc (isopinocampheyl) (see Table I)

ChemInform Abstract: Diastereoselective anti Aldol Reactions of Chiral Ethyl Ketones. Enantioselective Processes for the Synthesis of Polypropionate Natural Products.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Kinetic resolutions in anti aldol reactions with racemic 2-phenylthio aldehydes: asymmetric synthesis of cyclic ethers and lactones with phenylthio migration

Kinetic resolutions in Lewis acid catalysed asymmetric anti aldol reactions of the boron enolate of imide ( 2) with racemic 2-phenylthio aldehydes ( 3a) – ( 3c) give good yields of anti,anti aldols ( 7). Synthesis of homochiral cyclic ethers ( 4a) – ( 4c) and ( 5a) – ( 5c), and a simple novel route to homochiral lactones ( 6a) – ( 6c) are described.

Diastereoselective Anti Aldol Reactions of Chiral Ethyl Ketones. Enantioselective Processes for the Synthesis of Polypropionate Natural Products.

The diastereoselective anti aldol reactions of the β-keto imide 3a, the related ethyl ketone 20b, and its diastereomer 22b have been studied. In these aldol reactions, the chiral ethyl ketones 3a and 20b were found to exhibit the opposite sense of asymmetric induction in the analogous anti aldol bond constructions from the derived ( E) boron enolates. The relevance of this study to the synthesis of polypropionate natural products is discussed.

A stereoselective synthesis of hydroxyethylene and erythro-dihydroxyethylene dipeptide isosteres: a facial selective anti-Aldol reaction

A Lewis-acid catalyzed anti-aldol reaction of aldehyde 4 afforded diol 6a (95% de). Aminolysis of the corresponding β-lactone provided erythro-dihydroxyethylene dipeptide isostere 2 while the lactone-protected hydroxyethylene dipeptide isostere 3 was obtained through selective deoxygenation and acidic deprotection.