Intermolecular Cope‐Type Hydroamination of Alkenes and Alkynes

Beauchemin, André M.; Moran, Joseph; Lebrun, Marie-Eve; Séguin, Catherine; Dimitrijević, Elena; Zhang, Lili; Gorelsky, Serge I.

doi:10.1002/anie.200703495

Cited by 93 publications

(47 citation statements)

References 53 publications

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Section: Professor Dieter Enders Zum 65 Geburtstag Gewidmetunclassified

“…[16] Die Untersuchung des Reaktionsmechanismus dieser NHC-katalysierten Reaktion war aufschlussreich. [17] Zuerst konnte durch ein einfaches Deuterierungsexperiment die direkte Beteiligung der Sauerstoffverbrückung ausgeschlossen werden. [18] Dann wurde in einem Konkurrenzexperiment gezeigt, dass ein Phenylsubstituent am Olefin (R 2 = Ph, Schema 1) die Reaktivität im Vergleich zum nichtsubstituierten Olefin (R 2 = H) leicht erhöht.…”

Section: Professor Dieter Enders Zum 65 Geburtstag Gewidmetunclassified

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Hoch asymmetrische NHC‐katalysierte Hydroacylierung nichtaktivierter Alkene

et al. 2011

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Section: Professor Dieter Enders Zum 65 Geburtstag Gewidmetunclassified

Hoch asymmetrische NHC‐katalysierte Hydroacylierung nichtaktivierter Alkene

et al. 2011

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“…Nach der reversiblen Bildung des Breslow-Intermediats A [12,15] folgt dessen schrittweiser Angriff an das in situ gebildete Arin, wobei zunächst Zwitterion B mit negativer Ladung am aromatischen Ring gebildet wird und schließlich Umprotonierung das Alkoxid-Intermediat D liefert. [16] Alternativ ist auch ein konzertierter Übergangszustand [8,17] C möglich, analog zur Reaktion eines 1,3-Dipols mit einem Arin. [18] Jeder dieser letzteren Schritte scheint dabei schneller zu sein als die Bildung des Breslow-Intermediats.…”

Section: Akkattu T Biju Und Frank Glorius*unclassified

Eine intermolekulare, durch N‐heterocyclische Carbene katalysierte Hydroacylierung von Arinen

Biju

Glorius

2010

Angewandte Chemie

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Immer A‐rin damit! Eine konzeptionell neue, durch N‐heterocyclische Carbene (NHCs) katalysierte formale Insertion von Arinen in die CFormyl‐H‐Bindung von Aldehyden demonstriert die Kompatibilität von NHCs und elektrophilen Arinen. Diese NHC‐katalysierte Hydroacylierung von Arinen ermöglicht die Umsetzung aliphatischer, α,β‐ungesättigter und aromatischer Aldehyde zu Arylketonen. Es werden 27 Beispiele sowie erste mechanistische Experimente beschrieben.

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“…Finally, the NHC is released, thereby destroying the initially generated stereocenter and forming the final product 4. However, C might not be a local energy minimum of this reaction and a concerted conjugate addition/protonation mechanism [22,23] cannot be ruled out. In conclusion, we have developed an NHCcatalyzed enantioselective Stetter reaction with a highly stereoselective proton transfer as the key step that leads to amino acid derivatives.…”

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Highly Enantioselective Synthesis of α‐Amino Acid Derivatives by an NHC‐Catalyzed Intermolecular Stetter Reaction

2011

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Dedicated to Professor Ronald Breslow on the occasion of his 80th birthday a-Amino acids are one of the most important classes of compounds in nature and synthetic chemistry, and, consequently, many approaches have been developed for the synthesis of enantioenriched a-amino acids.[1] Among these synthetic routes, a particularly versatile and challenging method to set up the chirality at the a position of a-amino acids is the formation of a transient enolate through a Michael addition followed by a stereoselective protonation. Enantioselective protonation is important in many biosynthetic sequences, and the development of powerful catalytic processes remains an ongoing challenge. [2,3] Many different approaches for catalyzed enantioselective protonations have been realized; however, the combination of a conjugate addition with the asymmetric protonation of a transiently formed enolate stands out as being especially efficient and atom economic. [4][5][6] In the context of a-amino acid synthesis, this strategy was first explored by Pracejus et al. in 1977 for the synthesis of cysteine derivatives with moderate enantioselectivities (up to 54 % ee) by using methyl 2-phthalimidoacrylate as the Michael acceptor and cinchona alkaloids as the chiral catalysts. [7] More recently, asymmetric approaches based on the use of organocatalysts [4c] or metal-based catalysts [6] have shown improved selectivities, but the scope has remained limited.The cyanide or N-heterocyclic carbene (NHC) catalyzed [8] addition of an aldehyde to a Michael acceptor, the Stetter reaction, [8,9] is a versatile synthetic transformation. Whereas the intramolecular asymmetric Stetter reaction has been investigated extensively by the research groups of Enders, Rovis, and others, [8,10] the more versatile intermolecular asymmetric version has proven to be much more challenging. In the last two years, the first moderately to highly enantioselective intermolecular Stetter reactions were reported by the research groups of Enders [11] and Rovis, [12] and very recently an enzyme-catalyzed variant was reported by Müller and co-workers [13] (Scheme 1). However, selectivities are not yet optimal and the substrate scope seems to be very limited-a general system remains to be found. In addition, a stereocenter is formed in the b position in each of these cases. An asymmetric Stetter reaction that builds up only a stereocenters seems to be even more challenging. The key to success might be a highly stereoselective intramolecular proton transfer that relays the stereochemical information after the initial enantioselective attack of the Breslow intermediate on the Michael acceptor (Scheme 2). Herein we report a highly asymmetric intermolecular Stetter reacScheme 1. Chiral NHC- [11,12] or enzyme-catalyzed [13] intermolecular asymmetric Stetter reactions. EWG = electron-withdrawing group, Ar = aromatic group, Het = heteroaromatic group, R = rest.Scheme 2. Proposed reaction pathway for an intermolecular enantioselective Stetter reaction.

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Intermolecular Cope‐Type Hydroamination of Alkenes and Alkynes

Cited by 93 publications

References 53 publications

Hoch asymmetrische NHC‐katalysierte Hydroacylierung nichtaktivierter Alkene

Hoch asymmetrische NHC‐katalysierte Hydroacylierung nichtaktivierter Alkene

Eine intermolekulare, durch N‐heterocyclische Carbene katalysierte Hydroacylierung von Arinen

Highly Enantioselective Synthesis of α‐Amino Acid Derivatives by an NHC‐Catalyzed Intermolecular Stetter Reaction

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