First intramolecular enantioselective iridium-catalysed allylic aminations

Welter, Carolin; Koch, Oliver; Lipowsky, Gunter; Helmchen, Günter

doi:10.1039/b400023d

Cited by 114 publications

(49 citation statements)

References 14 publications

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“…[279] Cyclic amines 298 can be prepared in an analogous manner by the reaction of aminoallyl acetate 296 or aminoallyl carbonate 297 (Scheme 97). [280] Compared to the palladium-catalyzed allylation reaction, the iridium-or molybdenum-catalyzed allylation occurred at the more substituted end to afford the sterically and electronically preferred alkene-metal complexes, which may explain the preferred formation of the branched products. [281] 5.…”

Section: Intramolecular Reactionsmentioning

confidence: 99%

Metal‐Catalyzed Enantioselective Allylation in Asymmetric Synthesis

2007

Angew Chem Int Ed

1,358

431

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Metal-catalyzed enantioselective allylation, which involves the substitution of allylic metal intermediates with a diverse range of different nucleophiles or S(N)2'-type allylic substitution, leads to the formation of C-H, -C, -O, -N, -S, and other bonds with very high levels of asymmetric induction. The reaction may tolerate a broad range of functional groups and has been applied successfully to the synthesis of many natural products and new chiral compounds.

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Section: Intramolecular Reactionsmentioning

confidence: 99%

Metal‐Catalyzed Enantioselective Allylation in Asymmetric Synthesis

2007

Angew Chem Int Ed

1,358

431

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“…So wurden durch intramolekulare asymmetrische Aminierung der Benzylaminsubstituierten Allylcarbonate 186 die a-vinylsubstituierten Pyrrolidine, Piperidine und Azepane 187 synthetisiert (Schema 62 a). [315,316] Eine Totalsynthese von Centrolobin enthält eine Iridium/ Phosphoramidit-katalysierte Veretherung als einen der Schlüsselschritte. [325] In einer ähnlichen Anwendung entstehen durch Ir-katalysierte allylische Aminierung in Kombination mit einer Ringschlussmetathese cyclische b-Aminoalkoholderivate.…”

Section: Weitere Anwendungen Der Iridiumkatalysierten Asymmetrischen unclassified

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

2010

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Die asymmetrische Katalyse mit Übergangsmetallkomplexen ist die Grundlage unzähliger stereoselektiver Umwandlungen und hat damit das Bild der modernen Synthesechemie gewandelt. Der Schlüssel zum Erfolg war die Entwicklung chiraler Liganden zur Kontrolle der Regio‐, Diastereo‐ und Enantioselektivität. Dabei haben sich Phosphoramidite als eine äußerst vielseitige und leicht zugängliche Klasse von chiralen Liganden erwiesen. Ihre modulare Struktur ermöglicht die Herstellung von Ligandenbibliotheken und erleichtert die Feinabstimmung für eine bestimmte katalytische Reaktion. Phosphoramidite bewirken oft außerordentlich hohe Stereoselektivitäten, und ihre einzähnige Natur ist in der kombinatorischen Katalyse, die gemischte Liganden verwendet, unverzichtbar. In diesem Aufsatz werden neue Entwicklungen in der asymmetrischen Katalyse mit Phosphoramiditen diskutiert, wobei der Schwerpunkt auf der Bildung von Kohlenstoff‐ Kohlenstoff‐ und Kohlenstoff‐Heteroatom‐Bindungen liegt.

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“…Herein we report two convenient methods to generate the active catalyst in situ and the use of this catalyst to develop a general reaction of allylic carbonates with aromatic amines. [24] These reactions occur with a broad range of achiral, linear allylic carbonates to give branched chiral allyl aryl amines in excellent yields and with high regioand enantioselectivities (Scheme 2).…”

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confidence: 99%

Enantioselective Allylation of Aromatic Amines after In Situ Generation of an Activated Cyclometalated Iridium Catalyst

2004

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Aromatic amines with a stereocenter a to the nitrogen atom are important structural motifs in a number of biologically active compounds.[1] Many of approaches to such structures have been investigated, but each method has limitations. Thus, a highly enantioselective procedure to prepare optically active aromatic amines would be valuable, and an enantioselective route to N-aryl allylic amines would be particularly useful because of the dual functionality in these compounds.Allylic substitution catalyzed by transition metals has emerged as a powerful tool for enantioselective formation of CÀC, CÀN, and CÀO bonds. [2][3][4] However, aromatic amines have not been used commonly in allylic amination, [5][6][7] presumably because they are less nucleophilic than the more commonly used benzylamine or stabilized anionic nitrogen nucleophiles. A general and highly enantioselective reaction between an aromatic amine without an activating group on the nitrogen atom and an achiral allylic ester or a racemic branched allylic electrophile has not been reported.Catalysts based on metals other than palladium [8][9][10][11][12][13][14][15][16] and its congeners often form the more hindered, branched product from nucleophilic substitution with unsymmetrical monosubstituted allylic esters. [17][18][19][20] This reactivity complements the regioselectivity of palladium catalysts, which tend to form the linear products. We previously reported asymmetric allylic substitution of achiral allylic carbonates with aliphatic amines and phenoxides to form branched allylic amines and ethers with high regio-and enantioselectivities in the presence of an iridium complex with a phosphoramidite ligand. [21,22] Reactions of aromatic amines did not occur under the conditions developed originally.Our mechanistic studies have shown that the cyclometalated complex 1, generated in situ by treatment of [{Ir(cod)Cl} 2 ] (cod = cycloocta-1,5-diene) and the ligand L 1 with an alkylamine base (Scheme 1), is likely to be the true catalyst in the allylic amination.[23] Reactions conducted with the isolated complex 1 as catalyst occurred faster and with broader scope than those with the combination of [{Ir(cod)Cl} 2 ] and L 1 .We proposed that the initial system failed to catalyze reactions of anilines because aromatic amines are not basic enough to induce cyclometalation, not because aromatic amines are too weakly nucleophilic to react with the iridium allyl intermediate. [23] If so, then the reactions of aniline should occur with a catalyst generated in situ by the action of a separate additive. Herein we report two convenient methods to generate the active catalyst in situ and the use of this catalyst to develop a general reaction of allylic carbonates with aromatic amines.[24] These reactions occur with a broad range of achiral, linear allylic carbonates to give branched chiral allyl aryl amines in excellent yields and with high regioand enantioselectivities (Scheme 2).The cyclometalated complex 1 was generated in pure form by reaction of [{Ir(cod)Cl} 2 ] and...

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First intramolecular enantioselective iridium-catalysed allylic aminations

Abstract: Enantioselective iridium-catalysed intramolecular allylic aminations, using phosphinooxazolines or phosphorus amidites as ligands, provided ee values of >90%, at a catalyst loading of <0.5 mol-%, and displayed a marked preference for intra- over corresponding intermolecular reactions.

Cited by 114 publications

References 14 publications

Metal‐Catalyzed Enantioselective Allylation in Asymmetric Synthesis

Metal‐Catalyzed Enantioselective Allylation in Asymmetric Synthesis

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

Enantioselective Allylation of Aromatic Amines after In Situ Generation of an Activated Cyclometalated Iridium Catalyst

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