Base Catalyzed Asymmetric Induction of the Reaction of Methyl(phenyl)ketene with 1‐Phenylethanol: Method of Obtaining Hydratropic Acid in High Enantiomeric Purity

Jähme, Joachim; Rüchardt, Christoph

doi:10.1002/anie.198108852

Cited by 22 publications

(5 citation statements)

References 9 publications

(8 reference statements)

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“…One route to optically active arylpropionic acid derivatives involves the stereoselective addition of an alcohol to an arylalkylketene. Nearly all investigations of this process have relied upon the use of a stoichiometric amount of a chiral alcohol, such as ( R )-pantolactone, to induce asymmetry (up to 99.5:0.5; eq 17) …”

Section: 3 Asymmetric Protonations Of Ketenesmentioning

confidence: 99%

Chiral Dialkylaminopyridine Catalysts in Asymmetric Synthesis

2007

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Section: 3 Asymmetric Protonations Of Ketenesmentioning

confidence: 99%

Chiral Dialkylaminopyridine Catalysts in Asymmetric Synthesis

2007

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“…Such cavity is built from interlocking spheres centered on atoms or group of atoms. The radii of these spheres are 1.80 Å for N and O atoms, 2.28 Å for CH or CH 2 group of atoms, 2.4 Å for CH 3 , and 1.44 Å for H atoms of the hydroxyl groups. Within this approach, both the electrostatic and non-electrostatic components of the solvation energy were taken into account.…”

Section: Methodology and Computational Detailsmentioning

confidence: 99%

“…of the final product, being successful only those that use alcohols of limited availability as chiral reagents. [2][3][4] However, in 1989, Larsen et al 5 at Merck developed a synthetic route where naturally occurring a-hydroxy esters were used as chiral inductors, yielding very promising d.e.'s. They had reported that chiral 2-arylpropionic esters were obtained with a diastereoisomeric excess as high as 99% via a reaction of arylmethylketenes generated in situ with a variety of optically active a-hydroxy esters such as (R)-pantolactone.…”

Section: Introductionmentioning

confidence: 99%

An Alternative Mechanism for the 1,4-Asymmetric Induction in the Stereoselective Addition of (R)-Pantolactone to 2-Phenylpropylketene

Silva¹,

Silva²,

Barbosa³

et al. 2011

J. Braz. Chem. Soc.

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Um mecanismo alternativo para a indução assimétrica 1,4, na adição estereosseletiva da (R)-pantolactona ao 2-fenilpropilceteno foi investigado teoricamente. Um mecanismo envolvendo uma transferência de hidrogênio intermolecular foi proposto, que considera a participação ativa da dimetiletilamina e seu íon como agentes de transferência de hidrogênio. No primeiro passo, uma molécula de dimetiletilamina neutra interage com o anel de 7 membros do enol intermediário. Uma interação ácido-base específica é estabelecida entre o grupo hidroxila do enol e o átomo de nitrogênio da amina. A amina neutra é básica o suficiente para remover o hidrogênio. Uma outra molécula de amina protonada doa seu hidrogênio à ligação dupla C=C, para fornecer os produtos desejados. A estereoquímica foi definida pelo modo como as moléculas de amina neutra e protonada aproximam-se do enol. O excesso diasteroisomérico encontrado concorda com o dado experimental [para (S, R) e (R, R) é de 99:1].An alternative mechanism for the 1,4-assymmetric induction in the stereoselective addition of (R)-pantolactone to 2-phenylpropylketene was theoretically investigated. A mechanism involving an intermolecular proton transfer assisted by two amine molecules was proposed, which considered the active participation of the dimethylethylamine and its ion as proton transfer agents. In the first step, a neutral dimethylethylamine interacts with the seven-membered ring of the enol intermediate. A specific acid-base interaction is established between the hydroxyl group of the enol and the nitrogen atom of the dimethylethylamine. The neutral dimethylethylamine is basic enough to remove the proton. Another protonated dimethylethylamine is considered to donate its proton to the C=C double bond to give the desired products. The stereochemical outcome was defined by the way that the neutral and protonated dimethylethylamine approached to the enol. The diastereoisomeric ratio found is in good agreement with experiments [for (S, R) and (R, R) it is 99:1].

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“…The reaction of ketenes with various nucleophiles has been known since the beginning of the century and has been reviewed . Reaction with water generates carboxylic acids, , whereas addition of alcohols , or amines ,, yields esters and amides, respectively. Sulfur and phosphorus nucleophiles have also been shown to add to ketenes. , Most of the kinetic studies of ketene reactivity have focused on its hydration. ,− …”

Section: Introductionmentioning

confidence: 99%

Nucleophilicity toward Ketenes: Rate Constants for Addition of Amines to Aryl Ketenes in Acetonitrile Solution

Lucas

Andraos

et al. 2001

J. Org. Chem.

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Second-order rate constants (k(Nu)) have been measured for the addition of amines to ketenes 4-6 in acetonitrile solution by the laser flash photolysis technique. These ketenes are formed from a photochemical Wolff rearrangement of diazoketones 1-3, respectively. For all diazoketones studied, the presence of amines as nucleophiles in the reaction medium results in the formation of an intermediate that later converts to the amide. The rate of formation of these intermediates is linearly dependent on amine concentration. Various classes of amines, such as primary, secondary, and tertiary, aromatic, and aliphatic, have been used to investigate the ketene reactivity, and rate constants in the range 10(4)-10(9) M(-1) s(-1) have been measured. Reaction rates are dependent upon steric effects in both the ketene and the nucleophile, which is consistent with a reaction mechanism involving nucleophilic attack at Calpha in the molecular plane of the ketene. On the basis of these data, a set of N(+) parameters for the reaction of amines with ketenes was determined.

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Base Catalyzed Asymmetric Induction of the Reaction of Methyl(phenyl)ketene with 1‐Phenylethanol: Method of Obtaining Hydratropic Acid in High Enantiomeric Purity

Cited by 22 publications

References 9 publications

Chiral Dialkylaminopyridine Catalysts in Asymmetric Synthesis

Chiral Dialkylaminopyridine Catalysts in Asymmetric Synthesis

An Alternative Mechanism for the 1,4-Asymmetric Induction in the Stereoselective Addition of (R)-Pantolactone to 2-Phenylpropylketene

Nucleophilicity toward Ketenes: Rate Constants for Addition of Amines to Aryl Ketenes in Acetonitrile Solution

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