Chiral Dirhodium(II) Carboxamidate-Catalyzed [2+2]-Cycloaddition of TMS-Ketene and Ethyl Glyoxylate

Forslund, Raymond E.; Cain, J. R.; Colyer, John; Doyle, Michael P.

doi:10.1002/adsc.200404245

Cited by 46 publications

(18 citation statements)

References 13 publications

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“…Rh 2 (1 0 R,2 0 S,5 0 R,4S-MNACIM) 4 (6) has been previously described [26]. The synthesis of the diastereomer of 5, Rh 2 (1 0 S,2 0 R,5 0 S,4S-MNACIM) 4 (5), proceeded in an identical fashion (Scheme 4).…”

Section: Resultsmentioning

confidence: 99%

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Stereoselectivity in metal carbene and Lewis acid-catalyzed reactions from diastereomeric dirhodium(II) carboxamidates: Menthyl N-acetyl-2-oxoimidazolidine-4(S)-carboxylates

Doyle

Morgan

Colyer

2005

Journal of Organometallic Chemistry

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Section: Resultsmentioning

confidence: 99%

“…Configurational depictions of ''matched'' (A, complex 5) and ''mismatched'' (B, complex 6) dirhodium(II) 1-N-acetyl-2-oxaimidazolidine-4(S)-carboxylates, together with the front view of 6 showing only the attachments that are closest to the front rhodium[26].…”

mentioning

confidence: 99%

Stereoselectivity in metal carbene and Lewis acid-catalyzed reactions from diastereomeric dirhodium(II) carboxamidates: Menthyl N-acetyl-2-oxoimidazolidine-4(S)-carboxylates

Doyle

Morgan

Colyer

2005

Journal of Organometallic Chemistry

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“…As has already been demonstrated for the hetero-Diels-Alder reaction (Scheme 1) [1,2] and for trimethylsilylketene/glyoxal cycloaddition, [3] the chiral environment around the axial coordination site strongly influences enantiocontrol and also pushes the product off the rhodium axial coordination site to provide turnover numbers (TON) as high as 10 000. However, the Lewis acidity for dirhodium(II) carboxamidates is low compared to that of many other catalysts for these reactions.…”

mentioning

confidence: 89%

Cationic Chiral Dirhodium Carboxamidates Are Activated for Lewis Acid Catalysis

Wang¹,

Wolf²,

Zavalij³

et al. 2008

Angew Chem Int Ed

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Dedicated to Professor Henri Brunner on the occasion of his 72nd birthday Chiral dirhodium(II) carboxamidates have high potential for enantioselective Lewis acid catalyzed reactions because they hold the Lewis base, which is activated for reaction, at the axial coordination site in close proximity to the ligand attachments for chiral differentiation. As has already been demonstrated for the hetero-Diels-Alder reaction (Scheme 1) [1,2] and for trimethylsilylketene/glyoxal cycloaddition, [3] the chiral environment around the axial coordination site strongly influences enantiocontrol and also pushes the product off the rhodium axial coordination site to provide turnover numbers (TON) as high as 10 000. However, the Lewis acidity for dirhodium(II) carboxamidates is low compared to that of many other catalysts for these reactions.[4] Suitable Diels-Alder, ene, and dipolar cycloaddition reactions, for example, show no catalytic activity with chiral dirhodium(II) carboxamidates, even with a,adifluoro analogues of the mepy and meaz catalysts that were developed to enhance Lewis acid association with Lewis bases.[5] We have prepared cationic Rh II /Rh III counterparts to the moderately active chiral dirhodium(II) carboxamidates to enhance the Lewis acidity of these chiral dirhodium catalysts. Cationic metal complexes are now commonly used to achieve rate and selectivity enhancements for those transformations suitable to catalysis by the cationic metal complex.[6] We anticipated that cationic chiral Rh II /Rh III compounds could increase the closeness of association of the catalyst with Lewis bases, increase the rate of reaction with selected substrates, and enhance enantiocontrol.Oxidation of dirhodium(II) (Rh 2 4+ ) compounds is well known ,[6] but their Rh 2 5+ counterparts have been produced in the presence of either a less labile ligand such as halide [7] or by using another transition metal such as Ag I , Ce IV , or Cu II for the oxidation, [6,8] none of which are amenable to the use of Rh 2 5+ complexes as catalysts without laborious separation or further catalyst manipulation. However, we have recently discovered that nitrosonium salts effect facile oxidation of dirhodium(II) carboxamidates at room temperature to form the corresponding Rh II /Rh III salts quantitatively, evolving nitric oxide in the process. These complexes exhibit a characteristic electronic absorption near 1000 cm À1 . A crystal structure for the bis(acetonitrile) complex of [Rh 2 {(4S)-meox} 4 ]BF 4 is shown in Figure 1.To test the ability of chiral Rh 2 5+ carboxamidates to enhance selectivity in Lewis acid catalyzed transformations we turned our attention to the hetero-Diels-Alder reaction and to [Rh 2 (mepy) 4 ] as the catalyst. As has been reported, [1a] the use of 1.0 mol % [Rh 2 (mepy) 4 ] with p-nitrobenzaldehyde and the Danishefsky diene (see Scheme 1) resulted in the corresponding hetero-Diels-Alder product (53 % yield) in 73 % ee; use of the corresponding Rh 2 5+ complex, [Rh 2 {(5S)-mepy} 4 ]BF 4 , produced the same product in 93 %...

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“…Quite recently, Doyle and coworkers found that dirhodium(II) complexes such as rhodium(II) acetate and Rh 2 (4S-MEAZ) 4 (14) alsoact as highly active Lewis acidcatalysts (1 mol%) for the reaction of trimethylsilylketene and ethyl glyoxalate, affording the b-lactone15(Table4.6) [42].However, theuseofthechiralRh-complex, Rh 2 (4S-MEAZ) 4 , alone afforded almost no asymmetric induction (5% ee for (S)-isomer) (entry 2). The use of quinine (10 mol%) as a cobase catalyst to activate the ketene simultaneously provided exceptional enantiocontrol (99% ee) and enhanced reactivity (entry 5).…”

Section: Reactions Of Chiral Ammonium Ketene Enolates As Nucleophilesmentioning

confidence: 99%

“…Norbornene was reacted with various terminal alkynes in the presence of quinine-N-oxide (41) to afford the corresponding cyclopentenone derivatives (42) in low yields (27-68%) and ee values (2-30% ee) (Table 4.7) [62]. From the results listed in Table 4.7, hydrogen bonding between the alkyne and N-oxide plays an important role in controlling the enantioselectivity (Figure 4.4).…”

Section: Pauson-khand Reactionmentioning

confidence: 99%

Cinchona Alkaloids and their Derivatives as Chirality Inducers in Metal‐Promoted Enantioselective Carbon–Carbon and Carbon–Heteroatom Bond Forming Reactions

Deshmukh

Ryu

Song

2009

Cinchona Alkaloids in Synthesis and Catalysis

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Chiral Dirhodium(II) Carboxamidate-Catalyzed [2+2]-Cycloaddition of TMS-Ketene and Ethyl Glyoxylate

Cited by 46 publications

References 13 publications

Stereoselectivity in metal carbene and Lewis acid-catalyzed reactions from diastereomeric dirhodium(II) carboxamidates: Menthyl N-acetyl-2-oxoimidazolidine-4(S)-carboxylates

Stereoselectivity in metal carbene and Lewis acid-catalyzed reactions from diastereomeric dirhodium(II) carboxamidates: Menthyl N-acetyl-2-oxoimidazolidine-4(S)-carboxylates

Cationic Chiral Dirhodium Carboxamidates Are Activated for Lewis Acid Catalysis

Cinchona Alkaloids and their Derivatives as Chirality Inducers in Metal‐Promoted Enantioselective Carbon–Carbon and Carbon–Heteroatom Bond Forming Reactions

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