High Regio-, Chemo-, and Stereoselectivity via Low-Temperature 4 + 3 Cycloadditions. Convergent Synthesis of Multifunctionalized Vinylmetals (M = Si, Sn) and <i>S</i>-Vinyl Benzenecarbothioates

Beck, Hartmut; Stark, A.; Hoffmann, H. M. R.

doi:10.1021/ol991386p

Cited by 46 publications

(9 citation statements)

References 29 publications

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“…11 Hoffmann studied the asymmetric (4+3) cycloadditions of oxygen-stabilized oxyallyl cations generated from 10 by treatment with TMSOTf; their cycloadditions with 3-substituted furans led predominantly to anti-I adducts. 12 These results have recently been shown to conform to a CH–π mode of stereoinduction similar to that proposed for our oxyallyls 2 . 13 …”

Section: Introductionsupporting

confidence: 83%

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Stereoselectivities and Regioselectivities of (4 + 3) Cycloadditions Between Allenamide-Derived Chiral Oxazolidinone-Stabilized Oxyallyls and Furans: Experiment and Theory

et al. 2011

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A systematic investigation of the regioselectivities and stereoselectivities of (4+3) cycloadditions between unsymmetrical furans and a chiral oxazolidinone-substituted oxyallyl is presented. Cycloadditions were performed using an oxyallyl containing a (R)-4-phenyl-2-oxazolidinone auxiliary (2Ph), under either thermal or ZnCl2-catalyzed conditions. Reactions of 2Ph with 2-substituted furans gave syn cycloadducts selectively, while cycloadditions with 3-substituted furans gave selectively anti cycloadducts. The stereoselectivities were in favor of a single diastereoisomer (I) in all but one case (2-CO2R). Density functional theory calculations were performed to explain the selectivities. The results support a mechanism in which all cycloadducts are formed from the E isomer of the oxyallyl (in which the oxazolidinone C=O and oxyallyl oxygen are anti to each other) or the corresponding E ZnCl2 complex. The major diastereomer is derived from addition of the furan to the more crowded face of the oxyallyl. Crowded transition states are favored because they possess a stabilizing CH–π interaction between the furan and the Ph group.

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Section: Introductionsupporting

confidence: 83%

“…Similar anti-I selectivity was reported by Hoffmann for the cycloadditions of 3-substituted furans with related oxygen-substituted oxyallyl cations (Scheme 6). 12 …”

Section: Resultsmentioning

confidence: 99%

Stereoselectivities and Regioselectivities of (4 + 3) Cycloadditions Between Allenamide-Derived Chiral Oxazolidinone-Stabilized Oxyallyls and Furans: Experiment and Theory

et al. 2011

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“…The reaction of 2,5‐dimethylfuran with silyl enol ethers 15 and 18 a resulted in an almost 1:1 diastereomeric mixture of cycloadducts 25. In contrast, high regioselectivities and diastereoselectivities were achieved in cycloadditions with C3‐substituted furans (Scheme ).…”

Section: Asymmetric [4+3] Cycloaddition Reactionsmentioning

confidence: 99%

8‐Oxabicyclo[3.2.1]oct‐6‐en‐3‐ones: Application to the Asymmetric Synthesis of Polyoxygenated Building Blocks

2004

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The development and design of reliable and efficient methods for the construction of chiral building blocks are crucial in modern natural product synthesis. 8-Oxabicyclo[3.2.1]oct-6-en-3-ones are readily accessible scaffolds with defined stereochemical features which have been exploited for non-aldol approaches to the preparation of chiral building blocks. Strategies for their enantioselective synthesis, including asymmetric cycloaddition methods, desymmetrization protocols, and "racemic switch operations", are presented and evaluated.

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“…The use of nitrogen‐stabilized oxyallyl cations with unsymmetrical dienes in (4+3) cycloadditions has been reported to provide high levels of regioselectivity in many cases 16. 23, 24 However, there have been few systematic studies concerning the regioselectivity of oxyallyls and the influence of substituents on the diene 3e. 23 Furthermore, there had not been any coherent let alone predictive model reported for the regioselectivities in (4+3) cycloadditions.…”

Section: First Regiochemical Models In Oxyallyl Cation (4+3) Cycloaddmentioning

confidence: 99%

(4+3) Cycloaddition Reactions of Nitrogen‐Stabilized Oxyallyl Cations

Lohse

Hsung

2011

Chemistry A European J

208

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The use of heteroatom-substituted oxyallyl cations in (4 + 3) cycloadditions has had a tremendous impact on the development of cycloaddition chemistry. Extensive efforts have been exerted toward investigating the effect of oxygen-, sulfur-, and halogen-substituents on the reactivity of oxyallyl cations. Most recently, the use of nitrogen-stabilized oxyallyl cations has gained prominence in the area of (4 + 3) cycloadditions. The following article will provide an overview of this concept utilizing nitrogen-stabilized oxyallyl cations.

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High Regio-, Chemo-, and Stereoselectivity via Low-Temperature 4 + 3 Cycloadditions. Convergent Synthesis of Multifunctionalized Vinylmetals (M = Si, Sn) and S-Vinyl Benzenecarbothioates

Cited by 46 publications

References 29 publications

Stereoselectivities and Regioselectivities of (4 + 3) Cycloadditions Between Allenamide-Derived Chiral Oxazolidinone-Stabilized Oxyallyls and Furans: Experiment and Theory

Stereoselectivities and Regioselectivities of (4 + 3) Cycloadditions Between Allenamide-Derived Chiral Oxazolidinone-Stabilized Oxyallyls and Furans: Experiment and Theory

8‐Oxabicyclo[3.2.1]oct‐6‐en‐3‐ones: Application to the Asymmetric Synthesis of Polyoxygenated Building Blocks

(4+3) Cycloaddition Reactions of Nitrogen‐Stabilized Oxyallyl Cations

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