Nonenzymatic Dynamic Kinetic Resolution of α‐(Arylthio)‐ and α‐(Alkylthio)alkanoic Acids

Yang, Xing; Birman, Vladimir B.

doi:10.1002/anie.201007860

Cited by 50 publications

(11 citation statements)

References 40 publications

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“…Such processes, in fact, though rarely reported, have been observed by others. 157–159 We suspect that this unusual DKR is more common than is currently recognized.…”

Section: Resultsmentioning

confidence: 88%

Catalytic kinetic resolution of a dynamic racemate: highly stereoselective β-lactone formation by N-heterocyclic carbene catalysis

et al. 2014

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This study describes the combined experimental and computational elucidation of the mechanism and origins of stereoselectivities in the NHC-catalyzed dynamic kinetic resolution (DKR) of α-substituted-β-ketoesters. Density functional theory computations reveal that the NHC-catalyzed DKR proceeds by two mechanisms, depending on the stereochemistry around the forming bond: 1) a concerted, asynchronous formal (2+2) aldol-lactonization process, or 2) a stepwise spiro-lactonization mechanism where the alkoxide is trapped by the NHC-catalyst. These mechanisms contrast significantly from mechanisms found and postulated in other related transformations. Conjugative stabilization of the electrophile and non-classical hydrogen bonds are key in controlling the stereoselectivity. This reaction constitutes an interesting class of DKRs in which the catalyst is responsible for the kinetic resolution to selectively and irreversibly capture an enantiomer of a substrate undergoing rapid racemization with the help of an exogenous base.

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“…Such processes, in fact, though rarely reported, have been observed by others. 157–159 We suspect that this unusual DKR is more common than is currently recognized.…”

Section: Resultsmentioning

confidence: 88%

Catalytic kinetic resolution of a dynamic racemate: highly stereoselective β-lactone formation by N-heterocyclic carbene catalysis

et al. 2014

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“…DKR of aryl‐ and alkylthioalkanoic acids was developed through a similar process using benzoic anhydride to form the mixed anhydride with the substrate and DIPEA to promote the racemization of the stereocenter at room temperature (Scheme ).…”

Section: Itu‐catalyzed Reactions Involving Chiral Acylisothiouronimentioning

confidence: 99%

Enantioselective Catalysis by Chiral Isothioureas

et al. 2016

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International audienceThis review covers recent developments relating to organocatalyzed transformations by chiral isothioureas (ITUs) since their original introduction by Birman in 2006. This class of nucleophilic heterocycles was first involved in anhydride activation in enantioselective acyl transfer reactions, but it was more recently shown that activation of other reagents was possible, considerably enlarging their number of catalytic enantioselective transformations. Four main modes of activation as Lewis bases can currently be listed: (1) acylisothiouronium intermediates involved in acyl transfer, (2) silylisothiouronium species involved in silyl transfer, (3) acylisothiouronium enolates involved in several concerted and formal pericyclic transformations, and (4) α,_-unsaturated acylisothiouronium species involved in domino transformations. This review is organized according to these different modes of activation of chiral isothioureas

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“…a-Thio-substituted alkanoic acids: [31][32] In the course of our original study, [18] we explored the behavior of a-(phenylthio)propionic acid 36 under our standard conditions (at 0 8C) and produced the ester and the recovered starting material with 93 % ee and 41 % ee, respectively (Scheme 6 and Table 7, entry 1). This result, which translated into a selectivity factor of 39 at 31 % conversion, according to Kagans equation, [3a] was in reasonable agreement with that obtained with a-(phenoxy)propionic acid 13 ( Table 4, entry 1).…”

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confidence: 99%

Kinetic Resolution of α‐Substituted Alkanoic Acids Promoted by Homobenzotetramisole

Yang

Birman

2011

Chemistry A European J

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A new method for catalytic nonenzymatic kinetic resolution of α-substituted alkanoic acids has been developed, which relies on their activation with DCC followed by enantioselective alcoholysis of the intermediate symm-anhydrides in the presence of the amidine-based catalyst homobenzotetramisole (HBTM). Moderate to excellent selectivity factors (s=5-96) have been obtained in the case of several classes of substrates, namely, α-aryl-, α-aryloxy/alkoxy-, α-halo-, α-azido-, and α-phthalimido-alkanoic acids. Under similar conditions, α-(arylthio/alkylthio)-alkanoic acids undergo dynamic kinetic resolution providing corresponding esters in up to 92% ee and up to 93% yield.

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Nonenzymatic Dynamic Kinetic Resolution of α‐(Arylthio)‐ and α‐(Alkylthio)alkanoic Acids

Cited by 50 publications

References 40 publications

Catalytic kinetic resolution of a dynamic racemate: highly stereoselective β-lactone formation by N-heterocyclic carbene catalysis

Catalytic kinetic resolution of a dynamic racemate: highly stereoselective β-lactone formation by N-heterocyclic carbene catalysis

Enantioselective Catalysis by Chiral Isothioureas

Kinetic Resolution of α‐Substituted Alkanoic Acids Promoted by Homobenzotetramisole

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