Enantioselective catalysis XXIII. Aminoalcohol assisted decarboxylation of 2-carboxy-2-methyl-1-tetralone leading to enantioenriched 2-methyl-1-tetralone

Hénin, Françoise; Мuzart, Jacques; Nedjma, Mustapha; Rau, Hermann

doi:10.1007/bf00807568

Cited by 16 publications

(13 citation statements)

References 18 publications

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“…[27,35] 2-Methyl-1-tetralone-2-carboxylic acid benzyl ester (1) was prepared by acylation of 1-tetralone with diethyl carbonate and sodium hydride followed by methylation with methyl iodide under PTC conditions and transesterification with benzyl alcohol catalysed by titanium isopropoxide. Later, we used a procedure with the last two steps exchanged: transesterification of 1-tetralone-2-carboxylic acid ethyl ester was carried out first to provide 1-tetralone-2-carboxylic acid benzyl ester, which was subsequently methylated.…”

Section: Methodsmentioning

confidence: 99%

“…Keywords: b-keto esters · alkaloids · asymmetric catalysis · kinetic resolution · palladium lective protonation of enol intermediates formed by photochemical irradiation of a-disubstituted ketones. [35][36][37] The first enantioselective decarboxylation reaction was reported in 1904 by Marckwald. [38,39] Decarboxylation of malonic acid derivatives with copper salts and cinchona alkaloids was studied, [40][41][42] but it was shown later that the reaction is not copper-but base-catalysed.…”

Section: Introductionmentioning

confidence: 99%

“…[55] Here we report kinetic and spectroscopic studies using the transformation of 1 into 4 in the presence of ephedrine and the four major cinchona alkaloids as chiral bases in a frequently used test reaction (Scheme 1). [27,28,31,32,35] Results and Discussion General features of the domino reaction: We first analysed the influence of some key reaction parameters on the overall reaction rate and enantioselectivity in the transformation of rac-1 into 4. Five different alkaloids (1,2-amino alcohols) were tested in combination with a Pd/C catalyst ( Table 1).…”

Section: Introductionmentioning

confidence: 99%

“…[32] Only a small amount of a chiral amino alcohol (0.1-0.3 equiv) is required to provide a chiral product when starting from a benzyl b-keto ester, [26,35] and so the reaction was assumed to be catalytic. [24][25][26][27]35] Similarly, only catalytic amounts of amino alcohols are required for the enantioseAbstract: The kinetics and mechanisms of one-pot cascade reactions of racemic b-keto esters to give chiral ketones in the presence of Pd/C-chiral amino alcohol catalyst systems were studied. Transformation of 2-methyl-1-tetralone-2-carboxylic acid benzyl ester (1) into 2-methyl-1-tetralone (4) in the presence of Pd/C and cinchona alkaloids or ephedrine was chosen as a model reaction.…”

Section: Introductionmentioning

confidence: 99%

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Enantioselective Decarboxylation of β‐Keto Esters with Pd/Amino Alcohol Systems: Successive Metal Catalysis and Organocatalysis

Kukula

Matoušek

Mallát

et al. 2008

Chemistry A European J

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The kinetics and mechanisms of one-pot cascade reactions of racemic beta-keto esters to give chiral ketones in the presence of Pd/C-chiral amino alcohol catalyst systems were studied. Transformation of 2-methyl-1-tetralone-2-carboxylic acid benzyl ester (1) into 2-methyl-1-tetralone (4) in the presence of Pd/C and cinchona alkaloids or ephedrine was chosen as a model reaction. After the first reaction step, the Pd-catalysed debenzylation of 1 to afford the corresponding beta-keto acid (2), there are two possible reaction routes that may be catalysed by the chiral amino alcohol in solution or by Pd(0) sites on the metal surface in cooperation with the adsorbed amino alcohol. The reaction intermediate 2 was synthesized, and the kinetics of decarboxylation were followed by NMR, UV and IR spectroscopy. The studies revealed that the role of Pd is to trigger the reaction series by deprotection of 1. The subsequent dominant reaction route from the racemic beta-keto acid 2 to the chiral ketone 4 is catalysed by the chiral amino alcohol in the liquid phase. It is shown that kinetic resolution of the diastereomeric salt of rac-2 and the chiral amino alcohol plays a key role in the enantioselection. High enantioselectivity necessitates an amino alcohol/rac-2 ratio of at least 2. A high ratio favours the formation of 1:1 amino alcohol/acid diastereomeric complexes, and the second amino alcohol molecule may be responsible for the enantioselective protonation of 2 in the diastereomeric complex.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Enantioselective Decarboxylation of β‐Keto Esters with Pd/Amino Alcohol Systems: Successive Metal Catalysis and Organocatalysis

Kukula

Matoušek

Mallát

et al. 2008

Chemistry A European J

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“…[23] After the role of copper(I) in the decarboxylation of malonic acids had been minimized, [23,24,25] further investigations proved that the reaction is not copper(I)-catalyzed, but is induced by bases. [26,27] Thus, decarboxylations with CuCl are much slower than those with Cu 2 O, which contains the more basic oxide anion. Alkaloids as bases without any additives were able to initiate the decarboxylation.…”

Section: Decarboxylation Of Malonic Acids Their Monoesters and Cyanomentioning

confidence: 99%

Naproxen Derivatives by Enantioselective Decarboxylation

Brunner

Schmidt

2000

Eur. J. Org. Chem.

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Catalysed Asymmetric Protonation of Simple Linear Keto-Enolic Species − A Route to Chiral α-Arylpropionic Acids

et al. 2002

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The reaction cascade consisting of deprotection/decarboxylation/asymmetric protonation of enolic species, starting from open-chain benzyl β-oxo esters, has been studied. When carried out in the presence of catalytic amounts of cinchonine, the reaction gave optically active α-aryl ketonesThe enantioselective protonation of prostereogenic enol derivatives is conceptually simple, but the development of catalytic methods remains a challenge, especially in terms of rational design. [1] The methodologies currently in use are largely empirical and numerous parameters need to be considered. One general approach involves the generation of an enolate, which is protonated by a catalytic chiral protic source, which is in turn regenerated by an achiral stoichiometric proton donor. The generation of ketone enolates mainly makes use either of cleavage of enol ether derivatives by organometallic compounds, [2] or of nucleophilic addition to ketenes. [3] Under these conditions, high enantioselectivities can be achieved by the use of a great variety of chiral proton donors in association with achiral sources of moderate acidity. [4] The creation of two contiguous chiral centres by a sequence of asymmetric conjugated addition/protonation reactions between enones and thiols, catalysed by a chiral lithium complex, has recently been reported. [5] Another catalytic strategy utilises a transition metal with a chiral ligand for the formation of the enolic species, which can be protonated [6] or arylated [7] enantioselectively. We have used different methodologies (a photochemical activation [8,9] and a palladium-induced cascade reaction [10,11] ) to produce enolic species. The common feature of our procedures is the presence of a chiral amino alcohol in the key step, which interacts with the enolic species and promotes its enantioselective protonation. Thanks to the enol itself, the amino alcohol is regenerated, allowing its use in catalytic amounts, without any other proton source. Our preparation of optically active ketones, which starts from racemic β-oxo acids protected as benzyl β-oxo esters, corresponds to a cascade reaction involving deprotection, de- [a] with up to 75% ee. Enantio-enriched (S)-3-phenyl-2-butanone can be converted into 2-phenylpropionic acid without racemisation.carboxylation and final asymmetric protonation of the resulting enolic species. [10,11] The key step under these conditions is probably analogous to that observed with malonic acid derivative starting materials (Scheme 1). Advances in the field of asymmetric decarboxylation since the pioneering work of Marckwald [12] have been reviewed by Brunner. [13] The reaction is generally assisted by an alkaloid base (B*), allowing the formation of an ammonium carboxylate, which on decarboxylation affords an enolate, which is protonated by the ammonium group. [12Ϫ14] Naproxen derivatives can thus be prepared with ees up to 72% by use of a catalytic amount of an amide synthesised from cinchonine. [13,15] Scheme 1. Asymmetric decarboxylation of malonic derivati...

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Enantioselective catalysis XXIII. Aminoalcohol assisted decarboxylation of 2-carboxy-2-methyl-1-tetralone leading to enantioenriched 2-methyl-1-tetralone

Cited by 16 publications

References 18 publications

Enantioselective Decarboxylation of β‐Keto Esters with Pd/Amino Alcohol Systems: Successive Metal Catalysis and Organocatalysis

Enantioselective Decarboxylation of β‐Keto Esters with Pd/Amino Alcohol Systems: Successive Metal Catalysis and Organocatalysis

Naproxen Derivatives by Enantioselective Decarboxylation

Catalysed Asymmetric Protonation of Simple Linear Keto-Enolic Species − A Route to Chiral α-Arylpropionic Acids

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