Catalytic Enantioselective Silylation of <i>N</i>-Sulfonylimines: Asymmetric Synthesis of α-Amino Acids from CO<sub>2</sub> via Stereospecific Carboxylation of α-Amino Silanes

Mita, Tsuyoshi; Sugawara, Masayoshi; Saito, Keisuke; Sato, Yoshihiro

doi:10.1021/ol501143c

Cited by 102 publications

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References 71 publications

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“…[9,10] The starting enantioenriched N-tert-butylsulfonyl--amido silanes 1 can be synthesized either from Ellman's chiral sulfinyl imines by diastereoselective silylation [11] followed by oxidation or from sulfonyl imines by Cu(I)-catalyzed enantioselective silylation recently developed by our group. [10] In contrast, the use of NBoc--amido silanes 1b under the same conditions gave racemic compounds, [12] suggesting that the Boc substitution enhances carbanion generation, whereas the sulfonyl group might stabilize a fluorosilicate intermediate in the stereoretentive transformation.…”

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confidence: 99%

“…[16] This result suggested that the present nucleophilic addition proceeded in a retentive manner similar to the case of carboxylation of 1a. [10] One of the diastereomers of 2a (more polar product on silica gel column chromatography) derived from benzaldehyde as well as 2c (less polar product on silica gel column chromatography) derived from cyclohexanecarboxaldehyde For internal use, please do not delete. Submitted_Manuscript were both (S,S)-syn-diastereomers based on comparison of their NMR spectra and optical rotation values with the reported data ( Figure 6).…”

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“…Submitted_Manuscript were both (S,S)-syn-diastereomers based on comparison of their NMR spectra and optical rotation values with the reported data ( Figure 6). [17] In addition, the sulfonyl group of the other diastereomer of 2a was removed according to the reported methods, [10,18] giving the corresponding free amino alcohol 8 in 73% yield. Its optical rotation value and NMR spectra perfectly matched those of (S,R)-anti-diastereomer.…”

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Stereoretentive Addition of N‐tert‐Butylsulfonyl‐α‐Amido Silanes to Aldehydes, Ketones, α,β‐Unsaturated Esters, and Imines

Mita

Saito

Sugawara

et al. 2016

Chemistry An Asian Journal

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Abstract:Enantioenriched N-tert-butylsulfonyl--amido silanes were successfully reacted with aldehydes, ketones, imines, and ,-unsaturated esters in the presence of a sub-stoichiometric amount of CsF (0.5 equiv) in DME at -20 o C to afford the corresponding coupling products with up to 89% enantiospecificity in a retentive manner.The construction of C-C bonds with preservation of the optical purity of nucleophiles is a formidable challenge in organic synthesis. [1] Although transition-metal-catalyzed stereospecific cross-coupling reactions have been actively studied in this field, [2] much attention is still being paid to non-catalytic processes using highly reactive nucleophiles. [3][4][5][6] Among the latter examples, stereospecific additions of secondary and tertiary alkyllithium species have been extensively studied over the past three decades. [3] For instance, enantioenriched organolithium species, which are prepared by tin-lithium exchange from the corresponding optically active organostannanes and n-or s-BuLi, [4] deprotonation of enantioenriched carbamate-protected derivatives with BuLi and TMEDA, [5] or asymmetric deprotonation of achiral substrates using BuLi and (-)-sparteine as a chiral ligand, [6] reacted with a range of electrophiles in a stereoretentive/invertive manner. However, a very low temperature (below -78 o C) was often required in order to maintain their optical purities as much as possible. Moreover, the use of highly nucleophilic BuLi attenuates the synthetic utility due to the low functional group tolerability and the need for strictly anhydrous conditions. On the other hand, less reactive alkylboron [7] and silane [8] reagents were also employed for the stereospecific addition in combination with an appropriate activator. Although -addition of enantioenriched allylborons/silanes has already been established, [7a-d,8a-c] stereospecific transformation of C(sp 3 )-B/Si into C(sp 3 )-C bonds is still challenging, and this has motivated us to develop a new method with a high level of enantiospecificity for versatile electrophiles under mild conditions.Our research group already reported a stereoretentive carboxylation of -amino silanes 1 with CO 2 in the presence of CsF in DMF solvent at -20 o C, affording the corresponding -amino acids with up to 86% enantiospecificity (Figure 1). [9,10] The starting enantioenriched N-tert-butylsulfonyl--amido silanes 1 can be synthesized either from Ellman's chiral sulfinyl imines by diastereoselective silylation [11] followed by oxidation or from sulfonyl imines by Cu(I)-catalyzed enantioselective silylation recently developed by our group. [10] In contrast, the use of NBoc--amido silanes 1b under the same conditions gave racemic compounds, [12] suggesting that the Boc substitution enhances carbanion generation, whereas the sulfonyl group might stabilize a fluorosilicate intermediate in the stereoretentive transformation. We herein disclose the detection of a fluorosilicate species using 19 F-29 Si 2D NMR spectroscopy in addition to other p...

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Stereoretentive Addition of N‐tert‐Butylsulfonyl‐α‐Amido Silanes to Aldehydes, Ketones, α,β‐Unsaturated Esters, and Imines

Mita

Saito

Sugawara

et al. 2016

Chemistry An Asian Journal

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“…α-Halonitriles and sulfonyl halides are fast radical generators which have much faster initiation rate than propagation. They have been employed in the ATRP of acrylonitrile 15 , styrene 16 and acrylates 17 . …”

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confidence: 99%

“…The polymerization had a controlled manner and the PDI is less than 1.5. In the same year, Percec et al also published the ATRP of styrene using the same catalytic system, and the initiator was changed to arylsulfonyl chloride 16 . ATRP of MMA was achieved by using the 2-pyridinecarbaldehyde imine copper(I) complexes and an alkyl bromide as the initiator 28 .…”

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New Catalysts for Stereoselective Living Radical Polymerization of Functional α-Olefins

Nian

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New Catalysts for Stereoselective Living Radical Polymerization of Functional α-OlefinThe stereostructure of polymeric chains can greatly influence their physical and chemical properties. Therefore, controlling the stereostructures (tacticity) of polymers is very important in materials chemistry. There have been numerous studies on how to control the tacticity of polymer during a radical polymerization process. However, only a few monomers can be applied to stereospecific living radical polymerization.A Lewis acid-mediated stereocontrolled atom transfer radical polymerization (ATRP) of various acrylamide monomers was successfully achieved by using the newly had an isotacticity as high as 89% and a PDI of 1.12. It is the first time that the coppermediated stereocontrolled ATRP of N-isopropylacrylamide was successfully achieved.ii Acknowledgement I would like to give my deepest appreciation to my graduate advisor, Prof. Lin Pu, for his continuous guidance and help during my studies.

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Reactions of Aldehydes and Ketones and their Derivatives

Murray

2017

Organic Reaction Mechanisms · 2014

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Catalytic Enantioselective Silylation of N-Sulfonylimines: Asymmetric Synthesis of α-Amino Acids from CO₂ via Stereospecific Carboxylation of α-Amino Silanes

Cited by 102 publications

References 71 publications

Stereoretentive Addition of N‐tert‐Butylsulfonyl‐α‐Amido Silanes to Aldehydes, Ketones, α,β‐Unsaturated Esters, and Imines

Stereoretentive Addition of N‐tert‐Butylsulfonyl‐α‐Amido Silanes to Aldehydes, Ketones, α,β‐Unsaturated Esters, and Imines

New Catalysts for Stereoselective Living Radical Polymerization of Functional α-Olefins

Reactions of Aldehydes and Ketones and their Derivatives

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Catalytic Enantioselective Silylation of N-Sulfonylimines: Asymmetric Synthesis of α-Amino Acids from CO2 via Stereospecific Carboxylation of α-Amino Silanes

Cited by 102 publications

References 71 publications

Stereoretentive Addition of N‐tert‐Butylsulfonyl‐α‐Amido Silanes to Aldehydes, Ketones, α,β‐Unsaturated Esters, and Imines

Stereoretentive Addition of N‐tert‐Butylsulfonyl‐α‐Amido Silanes to Aldehydes, Ketones, α,β‐Unsaturated Esters, and Imines

New Catalysts for Stereoselective Living Radical Polymerization of Functional α-Olefins

Reactions of Aldehydes and Ketones and their Derivatives

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Catalytic Enantioselective Silylation of N-Sulfonylimines: Asymmetric Synthesis of α-Amino Acids from CO₂ via Stereospecific Carboxylation of α-Amino Silanes