The First Asymmetric Intramolecular <i>Stetter</i> Reaction. Preliminary Communication

Enders, Dieter; Breuer, K.; Runsink, Jan; Teles, J. Henrique

doi:10.1002/hlca.19960790712

Cited by 294 publications

(121 citation statements)

References 20 publications

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“…To date, experimental umpolung catalysts have enhanced stereoselectivity by increasing steric bulk on one face of the enolamine to promote exclusive reaction on the opposing face, [1,3,5,9,11,24] however the exact conformation of the enolamine has not been considered. Combined, the steric and electronic results herein indicate the balance between the E and Z isomers, which potentially lead to opposite stereochemical products, may not be as straight forward as expected, although tailoring the carbene substituents both electronically and sterically can be used to influence this ratio.…”

Section: Implications From the Model Reactionmentioning

confidence: 98%

“…Originally conceived by Stetter in the 1970's, [8] the first reports of a stereoselective reaction were reported by Enders in 1997 with chiral thiazolylidene based catalysts. [9] Initial yields and stereoselectivity were low, however improvements were quickly made by utilising intramolecular reactions. [10] Recently, Rovis and co-workers have made significant advancements in both the scope and selectivity of the reaction using triazole-based N-heterocyclic carbenes.…”

Section: Introductionmentioning

confidence: 99%

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The Mechanism of the Stetter Reaction – A DFT Study

Hawkes

Yates

2008

Eur J Org Chem

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On the basis of Breslow's mechanism for benzoin condensation, a model asymmetric Stetter reaction has been investigated using DFT methods. In contrast to the concerted benzoin condensation, after formation of the Breslow intermediate the Stetter reaction is found to be a two-step process in which the rate-determining C-C coupling of the Breslow intermediate and the Michael acceptor precedes final proton transfer. In addition, the enolamine is found to play a signifi-

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Section: Implications From the Model Reactionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

The Mechanism of the Stetter Reaction – A DFT Study

Hawkes

Yates

2008

Eur J Org Chem

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“…Initial studies were conducted with a triazolium salt in which the chiral substituent was attached to the nitrogen atom by an exocyclic single bond (up to 86% ee). [15] The same catalyst delivered up to 71% ee in intramolecular Figure 3. The chiral triazolium catalysts 6, [17] 7, [6] and 8 [7]  Stetter reactions (vide infra).…”

Section: Introductionmentioning

confidence: 97%

Preparation of Axially Chiral N,N′‐Diarylimidazolium and N‐Arylthiazolium Salts and Evaluation of Their Catalytic Potential in the Benzoin and in the Intramolecular Stetter Reactions

2004

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N-Aryl-substituted imidazoles 14b, 15b and thiazoles 17−22, 25 were prepared which contain a stereogenic axis and which can occur as atropisomers. The imidazolium salts 15b could be obtained from 2-isopropylaniline (12b) and diacetyl (11) in three steps (19% yield) whereas the synthesis of their tert-butyl analogues failed. The meso-isomer meso-15b prevailed (dr = 90/10). The chiral thiazolium salts rac-17 (53% yield) and rac-22 (49% yield) were prepared in two steps from 2-tert-butylaniline (12a). The enantiomerically pure thiazolium salt 19 was obtained from α-bromomenthone (23) and the aniline 12a (27% overall yield). In contrast to the imidazolium salts 15b, the thiazolium salts proved to be suit-

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“…Because aldehydes RCHO can also react with intermediates 81 and give products of benzoin homo-coupling, 81 must be more reactive toward 98 than RCHO for successful intermolecular Stetter reactions. Thus, intramolecular Stetter reactions have found a faster development than intermolecular Stetter reactions [345][346][347], including asymmetric versions [348][349][350]. Nevertheless, using acylsilanes 87 (Scheme 16) and enones of type 98 in the presence of DBU (base), THF (solvent) and thiazolium salt 100 (catalyst), good yields are obtained for the intermolecular Stetter reaction [351].…”

Section: The Stetter Reaction: Umpolung Of Aldehydementioning

confidence: 99%

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

et al. 2016

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Catalysis fulfills the promise that high-yielding chemical transformations will require little energy and produce no toxic waste. This message is carried by the study of the evolution of molecular catalysis of some of the most important reactions in organic chemistry. After reviewing the conceptual underpinnings of catalysis, we discuss the applications of different catalysts according to the mechanism of the reactions that they catalyze, including acyl group transfers, nucleophilic additions and substitutions, and C-C bond forming reactions that employ umpolung by nucleophilic additions to C=O and C=C double bonds. We highlight the utility of a broad range of organocatalysts other than compounds based on proline, the cinchona alkaloids and binaphthyls, which have been abundantly reviewed elsewhere. The focus is on organocatalysts, although a few examples employing metal complexes and enzymes are also included due to their significance. Classical Brønsted acids have evolved into electrophilic hands, the fingers of which are hydrogen donors (like enzymes) or other electrophilic moieties. Classical Lewis base catalysts have evolved into tridimensional, chiral nucleophiles that are N-(e.g., tertiary amines), P-(e.g., tertiary phosphines) and C-nucleophiles (e.g., N-heterocyclic carbenes). Many efficient organocatalysts bear electrophilic and nucleophilic moieties that interact simultaneously or not with both the electrophilic and nucleophilic reactants. A detailed understanding of the reaction mechanisms permits the design of better catalysts. Their construction represents a molecular science in itself, suggesting that sooner or later chemists will not only imitate Nature but be able to catalyze a much wider range of reactions with high chemo-, regio-, stereo-and enantioselectivity. Man-made organocatalysts are much smaller, cheaper and more stable than enzymes.

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The First Asymmetric Intramolecular Stetter Reaction. Preliminary Communication

Cited by 294 publications

References 20 publications

The Mechanism of the Stetter Reaction – A DFT Study

The Mechanism of the Stetter Reaction – A DFT Study

Preparation of Axially Chiral N,N′‐Diarylimidazolium and N‐Arylthiazolium Salts and Evaluation of Their Catalytic Potential in the Benzoin and in the Intramolecular Stetter Reactions

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

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