Zur Stereochemie der Katalyse

Bredig, G.; Fajans, K.

doi:10.1002/cber.190804101138

Cited by 87 publications

(19 citation statements)

References 21 publications

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“…[10] Fajans also reported the first examples of catalytic nonenzymatic KR (in the decarboxylation of camphor-3-carboxylic acid in the presence of chiral alkaloids; s = 1.1-1.5). His kinetic treatment would have shown that the ee value of unconverted substrate continuously increases as the conversion approaches 100 %, but only the product of decarboxylation (camphor) was assayed (with polarimetry).…”

Section: History Of Kinetic Resolutionmentioning

confidence: 95%

Efficiency in Nonenzymatic Kinetic Resolution

2005

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The Walden memorial at the Technical University in Riga is pictured in the frontispiece to mark the recent centennial of the Walden inversion. This is a rare public monument to key events from the first era of exploration in stereocontrolled synthesis, and may be the only such monument to use the language of organic chemistry expressed at the molecular level. The reaction of racemic substrates with chiral nucleophiles is one of many methods currently known to achieve kinetic resolution, a phenomenon that ranks as the oldest and most general approach for the synthesis of highly enantioenriched substances. The first nonenzymatic kinetic resolutions as well as the original forms of the Walden inversion were studied in the 1890s. All of these investigations were conducted within the first generation following the demonstration that carbon is tetrahedral, and provided abundant evidence that the principles and importance of enantiocontrolled syntheses were understood. However, a reliable, rapid technique to quantify results and guide the optimization process was still lacking. Many decades passed before this problem was solved by the advent of HPLC and GLPC assays on chiral supports, which stimulated explosive growth in the synthesis of nonracemic substances by kinetic resolution. The Walden monument is accessible to passers-by for hands-on inspection as well as for contemplation and learning. In a similar way, kinetic resolution is experimentally accessible and can be thought-provoking at several levels. We follow the story of kinetic resolution from the early discoveries through fascinating historical milestones and conceptual developments, and close with a focus on modern techniques that maximize efficiency.

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Section: History Of Kinetic Resolutionmentioning

confidence: 95%

Efficiency in Nonenzymatic Kinetic Resolution

2005

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“…In his early experiments he showed enantiomerical enrichment in the thermal decarboxylation of optically active camphorcarboxylic acid in d and l limonenes, respectively [25]. As an extension of this work he studied this decarboxylation reaction in the presence of chiral alkaloids, such as nicotine or quinidine, and established the basic kinetic equations of this kinetic resolution [26]. The first asymmetric CaC bond forming reaction is attributed also to his name.…”

Section: Historical Backgroundmentioning

confidence: 97%

Asymmetric Organocatalysis: A New Stream in Organic Synthesis

Dalko

2007

Enantioselective Organocatalysis

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In common with metal complexes and enzymes, small organic molecules may promote chemical transformations. Organocatalysis provides a means of accelerating chemical reactions with a substoichiometric amount of organic molecules, which do not contain a metal element [1,2].Despite this rich historical past, the use of small organic molecules as chiral catalysts has only recently been recognized as a valuable addition and/or alternative to existing, well-established, often metal-based methodologies in asymmetric synthesis. Driven both by distinguished scientific interest, which usually accompanies emerging fields, and the recognition of the huge potential of this new area, organocatalysis has finally developed into a practical synthetic paradigm [3][4][5][6][7][8][9][10][11][12][13][14][15]. The question must be asked, however, as to why it has taken so long for chemists to appreciate and exploit the potential of small organic molecules as chiral catalysts. Why was not the imagination of the vast majority of the chemical community captured by the perspectives of asymmetric organocatalysis, when metal complex-derived catalysis underwent steady development for enantioselective reactions?Principally, asymmetric organocatalytic reactions were, for a long time, considered to be inefficient and limited in scope. In parallel, organometallic catalysts provided a flexible ground for all types of reaction, and thus received disproportionate emphasis. Although today the vast majority of reactions in asymmetric catalysis continue to rely on organometallic complexes, this picture is changing, and organic catalysis is becoming an increasingly important segment of organic chemistry, offering a number of advantages over metal-based and bioorganic methods.Today, reactions can be performed under an aerobic atmosphere, with wet solvents; indeed, the presence of water is often beneficial to the rate and selectivity of the reaction. The operational simplicity and ready availability of these mostly inexpensive bench-stable catalysts -which are incomparably more robust than

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“…This reaction is generally enormously accelerated by amines [128,119] and proceeds at a variable rate with antipodes of optically active acids, when an optically active amine is used. Thus, Dcamphocarboxylic acid decomposes 13 % faster than the L-acid in the presence of L-nicotine [128]. This effect is even greater with (-)-threo-1 -p-nitrophenyl-2-aminopropanediol as catalyst, while on the other hand, the (+)-threo-isomer promotes the decomposition of the Lacid [ 1291.…”

Section: (16)mentioning

confidence: 99%