Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

Schörgenhumer, Johannes; Tiffner, Maximilian; Waser, Mario

doi:10.3762/bjoc.13.170

Cited by 54 publications

(25 citation statements)

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“…We have a strong research interest in asymmetric ammonium salt ion pairing catalysis, [10,11] with a special focus on asymmetric α-heterofunctionalizations of different (pro)-nucleophiles. [12] Considering the general potential of chiral ammonium salt catalysis for stereoselective α-heterofunctionalization reactions, [13] as well as for the asymmetric control of pronucleophiles 1, [8b] we now became interested in the development of new strategies for the synthesis of 3-heterofunctionalized isoindolinones 2 (i. e. CF 3 S-, RS-, F-substituted ones, Scheme 1B). [14,15,16,17,18]…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Bifunctional Ammonium Salt‐Catalyzed Syntheses of 3‐CF₃S‐, 3‐RS‐, and 3‐F‐Substituted Isoindolinones

et al. 2021

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We herein report the ammonium saltcatalyzed synthesis of chiral 3,3-disubstituted isoindolinones bearing a heteroatom functionality in the 3-position. A broad variety of differently substituted CF 3 Sand RS-derivatives were obtained with often high enantioselectivities when using Maruoka's bifunctional chiral ammonium salt catalyst. In addition, a first proof-of-concept for the racemic synthesis of the analogous F-containing products was obtained as well, giving access to one of the rare examples of a fairly stable α-F-α-amino acid derivative.

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Section: Introductionmentioning

confidence: 99%

Enantioselective Bifunctional Ammonium Salt‐Catalyzed Syntheses of 3‐CF₃S‐, 3‐RS‐, and 3‐F‐Substituted Isoindolinones

et al. 2021

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“…Surprisingly, however, the asymmetric α-azidation of commonly-employed β-ketoesters 3 has, to the best of our knowledge, not been systematically investigated using chiral non-covalent organocatalysis so far. Based on our research focus on asymmetric α-heterofunctionalization reactions [ 25 , 26 , 27 , 28 ], as well as our interest in the use of hypervalent iodine reagents under organocatalytic conditions [ 24 ], we have, therefore, now carried out detailed investigations of the α-azidation of ketoesters 3 with the electrophilic azide-transfer reagents 1 and 2 using the chiral organocatalysts C1 – C7 shown in Scheme 1 [ 26 , 29 , 30 , 31 , 32 ].…”

Section: Introductionmentioning

confidence: 99%

Towards an Asymmetric Organocatalytic α-Azidation of β-Ketoesters

et al. 2018

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Detailed investigations concerning the organocatalytic (asymmetric) α-azidation of prochiral β-ketoesters were carried out. It was shown that the racemic version of such a reaction can either be carried out under oxidative conditions using TMSN3 as the azide-source with quaternary ammonium iodides as the catalysts, or by using hypervalent iodine-based electrophilic azide-transfer reagents with different organocatalysts. In addition, the latter strategy could also be carried out with modest enantioselectivities when using simple cinchona alkaloid catalysts, albeit with relatively low yields.

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“…Reaction of acetate 7a with neutral carbon nucleophiles (dimethylamine, thiophenol and primary or secondary alcohols) led to the racemic products 70-72 in 65-95% yield (Scheme 30). 17,86 These products can be considered as further types of glycine cation equivalents.…”

Section: Cationic Glycine: Reactions With Neutral Heteroatom Nucleophmentioning

confidence: 99%

Benzophenone Schiff bases of glycine derivatives: Versatile starting materials for the synthesis of amino acids and their derivatives

O’Donnell

2019

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This review focuses on the introduction and early development, in solution, of phase-transfer catalyzed (PTC) reactions to afford racemic or enantioenriched natural and unnatural amino acids. To form monosubstituted amino acids alkylation reactions are performed on the benzophenone Schiff base of glycine. For α,α-disubstituted amino acids the activated intermediate is an aldimine derivative of the monosubstituted amino acid. Enantioenriched products are produced by organocatalysis using derivatives of Cinchona alkaloids as the phasetransfer catalyst. Selectivity for monoalkylatation and lack of product racemization depend on the acidities of the glycine imines, and dialkylated products are formed from aldimine esters of monoalkyl amino acids. The racemic and catalytic enantioselective reactions of a cationic glycine equivalent with organoboranes, organometallics and malonate anion are discussed as are other reactions of these versatile Schiff bases derivatives. Keywords Amino Acid Synthesis Unnatural Amino Acids Phase-Transfer Catalysis (PTC) Asymmetric Synthesis Benzophenone Schiff Bases Imines of Amino Acid Derivatives Organocatalysis Racemic and Stereoselective Reactions Glycine and Other Amino Acid Anion Equivalents Glycine Cation Equivalents Contents 10 9. Synthesis of α-methyl histidine by two complementary routes 11 10. PTC mono-or dialkylation with potassium carbonate 12 11. Intra-and intermolecular PTC dialkylations of a glycine equivalent 12 12. Acidities (pKa) of imine derivatives of glycine: Insights into alkylations 13 ___________________________________________________________________ This is the author's manuscript of the article published in final edited form as: O'Donnell, M. J. (2019). Benzophenone Schiff bases of glycine derivatives: Versatile starting materials for the synthesis of amino acids and their derivatives. Tetrahedron.

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Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

Cited by 54 publications

References 147 publications

Enantioselective Bifunctional Ammonium Salt‐Catalyzed Syntheses of 3‐CF₃S‐, 3‐RS‐, and 3‐F‐Substituted Isoindolinones

Enantioselective Bifunctional Ammonium Salt‐Catalyzed Syntheses of 3‐CF₃S‐, 3‐RS‐, and 3‐F‐Substituted Isoindolinones

Towards an Asymmetric Organocatalytic α-Azidation of β-Ketoesters

Benzophenone Schiff bases of glycine derivatives: Versatile starting materials for the synthesis of amino acids and their derivatives

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Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

Cited by 54 publications

References 147 publications

Enantioselective Bifunctional Ammonium Salt‐Catalyzed Syntheses of 3‐CF3S‐, 3‐RS‐, and 3‐F‐Substituted Isoindolinones

Enantioselective Bifunctional Ammonium Salt‐Catalyzed Syntheses of 3‐CF3S‐, 3‐RS‐, and 3‐F‐Substituted Isoindolinones

Towards an Asymmetric Organocatalytic α-Azidation of β-Ketoesters

Benzophenone Schiff bases of glycine derivatives: Versatile starting materials for the synthesis of amino acids and their derivatives

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Enantioselective Bifunctional Ammonium Salt‐Catalyzed Syntheses of 3‐CF₃S‐, 3‐RS‐, and 3‐F‐Substituted Isoindolinones

Enantioselective Bifunctional Ammonium Salt‐Catalyzed Syntheses of 3‐CF₃S‐, 3‐RS‐, and 3‐F‐Substituted Isoindolinones