Synthesis of novel chiral bis(2-oxazolinyl)xanthene (xabox) ligands and their evaluation in catalytic asymmetric 1,3-dipolar cycloaddition reactions of nitrones with 3-crotonoyl-2-oxazolidinone

Iwasa, Seiji; Ishima, Yosuke; Widagdo, Herman Setyo; Aoki, Katsuyuki; Nishiyama, Hisao

doi:10.1016/j.tetlet.2004.01.043

Cited by 33 publications

(10 citation statements)

References 35 publications

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“…148,149 Diastereoselectivities of 96:4 to 98:2 were achieved with enantiomeric excesses of 91-95% ee. …”

Section: Manganese Catalystsmentioning

confidence: 97%

“…Nishiyama and co-workers have developed a series of tridentate oxazoline-derived chiral ligands having a xanthene backbone, and have studied the cycloaddition of nitrones such as 78 to the oxazolidinone 75 in the presence of these ligands. 148,149 The xabox-Bn-Mg(II) complex 65 yielded diastereoselectivities of up to >99:1 with % ee's of the endo-isomer ranging from 85-96% (entries 13 and 14, Table 3). A transition state similar to that outlined in Figure 27 can be envisioned, with the diastereofacial selectivity due to the endo attack of the nitrone 78 on the Re face of the alkene 75.…”

Section: Figure 27mentioning

confidence: 99%

“…164 Nishiyama and co-workers have developed a series of tridentate oxazoline-derived chiral ligands having a xanthene backbone, and have studied the cycloaddition of nitrones such as 78 to the oxazolidinone 75 in the presence of these ligands. 148,149 The xabox-Bn-Mg(II) complex 65 yielded 158 Pr Ph Yb(OTf) 3 92 : 8 -32 158 Me Ph Sc(OTf) 3 93 : 7 -33 158 Pr Ph Sc(OTf) 3 82 : 18 -34 158 Me Ph Yb(III)-Pybox 73 95 : 5 67 35 159 Me diastereoselectivities of up to >99 : 1 with % ee's of the endoisomer ranging from 85 to 96% (entries 13 and 14, Table 3).…”

Section: Titanium Catalystsmentioning

confidence: 99%

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Asymmetric 1,3-dipolar cycloadditions of acrylamides

2010

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This critical review, which is relevant to researchers in synthetic organic chemistry, focuses on asymmetric 1,3-dipolar cycloadditions with acrylamides. The use of chiral acrylamides as dipolarophiles leads to high levels of stereocontrol, due to conformational constraint in the acrylamides. Employment of chiral tertiary acrylamides containing nitrogen heterocycles is particularly effective in controlling the stereoselectivity. Following a general overview of 1,3-dipolar cycloadditions, the main body of the review focuses on asymmetric 1,3-dipolar cycloadditions of acrylamides with nitrile oxides, nitrones, diazoalkanes and azomethine ylides, with particular emphasis on the rationale for the observed stereocontrol (215 references)

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“…148,149 Diastereoselectivities of 96:4 to 98:2 were achieved with enantiomeric excesses of 91-95% ee. …”

Section: Manganese Catalystsmentioning

confidence: 97%

Section: Figure 27mentioning

confidence: 99%

Section: Titanium Catalystsmentioning

confidence: 99%

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Asymmetric 1,3-dipolar cycloadditions of acrylamides

2010

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“…(136)). Recently, this research group introduced the chiral bis(2-oxazolinyl)xanthene (xabox) as another group of chiral ligands that showed applicability to the catalytic asymmetric cycloaddition of nitrones [373]. Recently, this research group introduced the chiral bis(2-oxazolinyl)xanthene (xabox) as another group of chiral ligands that showed applicability to the catalytic asymmetric cycloaddition of nitrones [373].…”

Section: Five-membered Heterocyclesmentioning

confidence: 99%

Recent Advances in Catalytic Asymmetric Addition to Imines and Related C=N Systems

Vilaivan¹,

Bhanthumnavin²,

Sritana-anant

2005

COC

150

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Addition reactions to imines are relatively less developed compared to those of carbonyl compounds due to low electrophilicity and ease of α-deprotonation. With the use of an appropriate activator, which can coordinate to the imine nitrogen atom, the electrophilicity of the imine can be enhanced and a range of nucleophilic addition reactions becomes possible. When the activator is chiral, it will also create chiral environment and will direct the approach of the nucleophile to one face of the imine over the other resulting in enantioselectivity. The potential of catalytic asymmetric addition to imines in organic synthesis is enormous, but is relatively underused. With the development of many highly effective chiral catalysts for imine additions, the situation will soon be changed. The present review will cover selected literature on catalytic asymmetric additions to aldimines, ketimines and related compounds including hydrazones, oximes and nitrones from 1999 to 2004. The reactions of interest include hydrogenation, alkylation, Mannich and related reactions such as aza-Baylis-Hillman and aza-Henry reaction, Strecker reaction, hydrophosphonylation, and 3-6 membered ring forming reactions from imines. Some applications of these methodologies in synthesis of nitrogen-containing biologically active compounds will also be presented.

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“…In this report, we disclose a new type of xanthene-based N,O,N-ligand, 4,5-bis(2-oxazolinyl)xanthene (Xabox) with a facial configuration and its rhodium complexes obtained by stereoselective oxidative additions with chloroacetate and diynes. In this context, we have already reported chiral Xabox derivatives and the application for the asymmetric catalytic 1,3-dipolar cycloaddition of nitrones and enones with nickel-salt catalysts [6] (Chart 1).…”

Section: Introductionmentioning

confidence: 99%