Enantioselective Catalysis by Chiral Solids: Approaches and Results.

Blaser, Hans‐Ulrich; Müller, Manfred

doi:10.1016/s0167-2991(08)61108-8

Cited by 100 publications

(19 citation statements)

References 47 publications

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“…The other ligands tested have a less rigid backbone (PROPHOS) or form larger and more flexible chelates (e.g., DIOP or BPPM). This rather empirical analysis does of course not explain why ethyl benzoylformate 3 and the a-keto acid 4 are unsuitable substrates for the [Rh(NBD)C12/(2S,3S)-NORPHOS catalyst because in principle both could form similar catalyst substrate complexes as the aliphatic a-keto esters. It also does not explain the observed solvent effect.…”

Section: Discussionmentioning

confidence: 96%

A highly enantioselective rhodium catalyst for the hydrogenation of aliphatic α‐keto esters

1991

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The enantioselective hydrogenation of several a-keto acid derivatives with rhodium diphosphine catalysts has been investigated using a random screening approach. The neutral rhodium catalyst prepared in situ from bis(2,5-norbornadiene rhodium chloride) and NORPHOS has been found to be an excellent catalyst for preparing aliphatic a-hydroxy esters in high optical purities. The reaction parameters for the hydrogenation of ethyl 2-0~0-4-phenyl-butyrate, an intermediate for the ACE inhibitor Benazepril, were optimized and the best optical yields obtained were 96%.

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Section: Discussionmentioning

confidence: 96%

A highly enantioselective rhodium catalyst for the hydrogenation of aliphatic α‐keto esters

1991

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“…31 Opposite to aforementioned results the N1 alkyl derivatives of cinchonas completely lost the enantiodifferentiation ability in the hydrogenation of a-ketoesters. 21,23,32 In the hydrogenation of racemic 2-fluorocyclohexanone the N-methyl salt of cinchonidine has also resulted in racemic products, 31 similarly to most of the studied activated ketones. 33,34 The only exception of substrates is ketopantolactone, 35 which has been successfully hydrogenated over Pt/Al 2 O 3 in the presence of N-alkylated cinchonidine derivatives such as N-methyl-cinchonidine-chloride, N-benzyl-cinchonidine-chloride and 1-methyl-9-methoxy-cinchonidine-chloride (see Fig.…”

Section: Flexible Cinchona Derivativesmentioning

confidence: 94%

“…It was concluded that the configuration of C8 or C8 and C9 atoms of the template molecule determine the product distribution. [23][24][25] This statement has widely been accepted but it is necessary to refine this picture according to the latest results. Upon using epicinchona alkaloids as chiral templates in the hydrogenation of ethyl pyruvate epiquinine [C8(S), C9(S)] resulted in 42% ee [(R)-lactate], whereas epiquinidine [(C8(R), 9(R)] gave 22% ee [(S)-lactate] at a conversion of 97%.…”

Section: Flexible Cinchona Alkaloidsmentioning

confidence: 99%

Natural alkaloids and synthetic relatives as chiral templates of the Orito's reaction

Tálas¹,

Margitfalvi²

2009

Chirality

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The enantioselective hydrogenation of methyl or ethyl pyruvate over cinchona-platinum catalyst system (Orito's reaction) is one of the most intensively studied heterogeneous catalytic asymmetric hydrogenation reactions. Studies aiming at systematic changes of the chiral template have played a crucial role in creating hypotheses for the mechanism of Orito's reaction. It is very important to clarify which structural unit of the alkaloid takes part in the enantiodifferentiation, and learn about the role of the different structural units of chiral templates. In this article, we made an attempt to describe the behavior of natural alkaloids, their synthetic derivatives, and analogues as chiral templates in the heterogeneous catalytic asymmetric hydrogenation of activated ketones.

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“…Until recently, only two families of heterogeneous, asymmetric catalytic systems existed: (i) a Raney-Ni catalyst modified with tartrate/NaBr and (ii) Pt (or Pd) catalysts modified with cinchona alkaloids. These two systems show low enantiomeric excesses (88's) relative to homogeneous systems and work on only small classes of chemical compounds (Blaser and Muller, 1991).…”

Section: Asymmetric Catalysismentioning

confidence: 99%

Catalysis for Environmentally Benign Processing

Dartt¹,

Davis²

1994

Ind. Eng. Chem. Res.

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A short overview of the types of catalytic processes that have shown progress in creating clean technology and are likely through continued material improvements to lead to new environmentally benign processing is presented. Chemistries involving solid acidhase catalysis, clean oxidation catalysis, catalysis in water, and asymmetric catalysis are discussed. Suggested reactions and catalytic materials for future clean processing are enumerated and unifying concepts for implementing catalysis for environmentally benign technologies are outlined.

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Enantioselective Catalysis by Chiral Solids: Approaches and Results.

Cited by 100 publications

References 47 publications

A highly enantioselective rhodium catalyst for the hydrogenation of aliphatic α‐keto esters

A highly enantioselective rhodium catalyst for the hydrogenation of aliphatic α‐keto esters

Natural alkaloids and synthetic relatives as chiral templates of the Orito's reaction

Catalysis for Environmentally Benign Processing

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