Immobilization of asymmetric multifunctional catalysts on an insoluble polymer

Matsunaga, Shigeki; Ohshima, Takashi; Shibasaki, Masakatsu

doi:10.1016/s0040-4039(00)01486-6

Cited by 79 publications

(39 citation statements)

References 9 publications

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“…These efforts resulted in the so-called linkedbinol system 6 b (Scheme 3), which combines all the desired attributes. [14,15] For the synthesis of tertiary stereocenters, this type of catalyst is almost optimal with regard to stereoselectivity, handling, and reuse. However, as exemplified in Scheme 3 for the preparation of 4 f, these expectations cannot be extended to quaternary stereocenters (75 % ee at À30 8C).…”

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confidence: 99%

Construction of Quaternary Stereocenters: New Perspectives through Enantioselective Michael Reactions

2003

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Stereoselective C À C bond-forming reactions are of particular importance for the preparation of enantiopure natural compounds and pharmaceuticals. The wide variety of available chiral auxiliaries, reagents, and catalysts nowadays enables the generation of tertiary stereocenters in most cases without any difficulty. However, the approach to complex compounds with quaternary stereocenters is still a challenge for synthetic organic chemists, and every enantioselective procedure in which a fully substituted carbon center is constructed is of value.[1]The Michael reaction, the conjugated or 1,4-addition of enolates to acceptor-substituted olefins, is a fundamental CÀC-coupling reaction, which is catalyzed not only by Brønsted bases, [2] but also by a number of metal compounds. [3] An important breakthrough in the field of extensively investigated metal-catalyzed, enantioselective Michael reactions [4] was recently reported by Sodeoka and co-workers.[5] For the first time, quaternary stereocenters could be generated with > 90 % ee at a relatively high temperature of À20 8C in a Michael reaction of b-dicarbonyl compounds 1 with enones 2 using palladium(ii) as the catalytically active transition metal. The Pd II -diaquadiphosphane complexes 3 a and 3 b are formed with chiral ligands (R)-tol-binap and (R)-binap, respectively. Scheme 1 shows four typical reaction products 4 a-d as examples.Both cyclic (1 a) and acyclic (1 b) bketoesters react with methyl vinyl ketone (2 a) at À20 8C in a Michael reaction promoted by 3 a to give the corresponding products 4 a and 4 b in moderate to good yields with > 90 % ee. Noteworthy is the use of the sterically demanding tert-butyl and phenyl b-ketoesters. The conversion of b-diketone 1 c (X = CH 2 Ar) in the presence of catalyst 3 b (10 mol %) at À10 8C is an outstanding example of an asymmetric Michael addition to acyclic triketones such as 4 c with very high stereoselectivity, an achievement thus far not reported in the literature. Furthermore, the reaction of 1 d with substituted enone 2 b catalyzed by 3 b at À20 8C affords a mixture of two diastereoisomers (d.r. = 8:1), and an enantiomeric excess of 99 % for the major diastereomer of 4 d.The high efficiency of the method developed by Sodeoka and co-workers is clearly demonstrated in view of the work published so far: In 1975 Wynberg and co-workers applied cinchona alkaloids in base-catalyzed, enantioselective Michael reactions.[6] About 10 years later, the first of these reactions catalyzed by a transition metal, cobalt, was published by Brunner and Hammer.[7] Both methods result in quaternary stereocenters with up to 68 % ee, which was improved in the following years by Desimoni et al. to 75 % ee.

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confidence: 99%

Construction of Quaternary Stereocenters: New Perspectives through Enantioselective Michael Reactions

2003

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“…Beide Arbeitsgruppen setzten auch Cyanformiat-Derivate als alternative Cyanierungsreagentien ein, [41b, 42] Der immobilisierte, Polymer-verankerte Linked-BinolLanthan-Katalysator 36 lieferte mäßige bis gute ee-Werte (bis zu 78 %). [53] Ein weiterer immobilisierter Katalysator, der Poly-Al-Li-Binol-Katalysator 37 von Sasai et al, ergab Michael-Addukte mit hohen ee-Werten (93 % ee für 2-(3-Oxocyclohexyl)malonsäuredibenzylester). [54] Polymer-gebundene Katalysatoren führen jedoch zurzeit noch zu unbefriedigenden Enantioselektivitäten.…”

Section: Asymmetrische Reduktion Von Carbonyl-verbindungen Mit Boranenunclassified

Hoch effiziente asymmetrische Katalyse durch doppelte Aktivierung von Nucleophil und Elektrophil

Ma¹,

Cahard²

2004

Angewandte Chemie

142

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Die Entwicklung neuer Hochleistungs‐Katalysatoren für asymmetrische Katalysereaktionen ist für die Organische Chemie von dauerhaftem Interesse. Eine aktuelle Methode bei der stereoselektiven Synthese ist die Verwendung einer Kombination von Lewis‐Säure und Lewis‐Base. Der Synergieeffekt durch die Aktivierung mithilfe von zwei oder mehr reaktiven Zentren führt zu hohen Reaktionsgeschwindigkeiten und zu einer hervorragenden Übertragung der stereochemischen Information. Obwohl durch die unerwünschte Reaktion der Lewis‐Säure mit der Lewis‐Base der Katalysator inaktiviert werden kann, wird das Konzept der doppelten Aktivierung mit großem Aufwand weiterentwickelt. Das Ziel ist die Herstellung biomimetischer Katalysesysteme auf der Grundlage enzymatischer Prozesse mit cokatalytischen Metallionen. Doppelt aktivierende Katalysatorsysteme erweitern die Zahl bereits bekannter Katalysatoren beträchtlich. Die effektivsten dieser Systeme werden in diesem Aufsatz erörtert und die Wirkungsmechanismen diskutiert.

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“…Although there was a severe decrease in reactivity and selectivity with polymer-supported La-linked-BINOL complex 42, the use of a new polymer-supported LaZn-linked-BINOL complex 43 ( Figure 11) improves reactivity in the Michael reaction. [44] A homogeneous La-Zn-linked-BINOL complex was also effective in the Michael reaction of cyclic enones with malonates to afford products in good enantiomeric excess. [44] In the case of La-Zn-linked-BINOL complex, the Zn-naphthoxide moiety is considered to function as a Br˘nsted base.…”

Section: La-linked-binol Complex: Development Of Stable Storable Andmentioning

confidence: 99%

“…[44] A homogeneous La-Zn-linked-BINOL complex was also effective in the Michael reaction of cyclic enones with malonates to afford products in good enantiomeric excess. [44] In the case of La-Zn-linked-BINOL complex, the Zn-naphthoxide moiety is considered to function as a Br˘nsted base. The use of mild and selective Zn species finally led to the development of a new multifunctional asymmetric catalysis, which will be discussed in the next section.…”

Section: La-linked-binol Complex: Development Of Stable Storable Andmentioning

confidence: 99%

Linked-BINOL: An Approach towards Practical Asymmetric Multifunctional Catalysis

Matsunaga

Ohshima

Shibasaki

2002

Advanced Synthesis & Catalysis

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116

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Immobilization of asymmetric multifunctional catalysts on an insoluble polymer

Cited by 79 publications

References 9 publications

Construction of Quaternary Stereocenters: New Perspectives through Enantioselective Michael Reactions

Construction of Quaternary Stereocenters: New Perspectives through Enantioselective Michael Reactions

Hoch effiziente asymmetrische Katalyse durch doppelte Aktivierung von Nucleophil und Elektrophil

Linked-BINOL: An Approach towards Practical Asymmetric Multifunctional Catalysis

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