Use of Chiral Quaternary Salts in Asymmetric Synthesis

Shioiri, Takayuki; Andõ, Akira; Masui, Masao; Miura, Toshio; Tatematsu, Toshiaki; Bohsako, Akemi; Higashiyama, M.; Asakura, Chiharu

doi:10.1021/bk-1997-0659.ch011

Cited by 19 publications

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“…Phase-transfer catalysis (PTC, Scheme 2B) was developed as a practical synthetic procedure by Makosza, 21 Dehmlow, 22 Starks 23 and others. 24 The first PTC alkylation of…”

Section: Phase-transfer Alkylations Of the Schiff Base Esters Of Glycmentioning

confidence: 99%

“…QX; 5B, 10% QX) (Scheme 5B). 8,[21][22][23][24] The Schiff base 4b from 4-chlorobenzaldehyde and glycine ethyl ester was chosen over the Schiff base of benzaldehyde and glycine ethyl ester (4a) because the former is crystalline. The ion-pair extractive alkylation of 5a resulted in good to excellent yields of both active (benzylic, 91-94%, allylic, 76%) and less reactive alkyl (EtI, 76%) halides except when an alkyl iodide (nOctBr) was used.…”

Section: Monoalkylation: Ketimine (Ipe) Vs Aldimine (Ptc) Glycine Etmentioning

confidence: 99%

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

O’Donnell

2019

Tetrahedron

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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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“…Phase-transfer catalysis (PTC, Scheme 2B) was developed as a practical synthetic procedure by Makosza, 21 Dehmlow, 22 Starks 23 and others. 24 The first PTC alkylation of…”

Section: Phase-transfer Alkylations Of the Schiff Base Esters Of Glycmentioning

confidence: 99%

Section: Monoalkylation: Ketimine (Ipe) Vs Aldimine (Ptc) Glycine Etmentioning

confidence: 99%

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

O’Donnell

2019

Tetrahedron

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“…The reaction gave aldol product 11 in low yield and stereoselectivity. 9 Lectka and coworkers applied the tol-BINAP-derived bis-phosphonium fluoride catalyst 9 to highly diastereoselective synthesis of β-lactam 14 via cycloaddition with ketene silyl acetal 12 and imine 13. 10 Although high diastereoselectivity was reported in this reaction, the enantioselectivity of product 14 was not mentioned in this report.…”

Section: Methodsmentioning

confidence: 99%

Chiral quaternary phosphonium salts as phase-transfer catalysts for environmentally benign asymmetric transformations

2016

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“…In 1997, Shioiri et al. communicated the first report on a phosphonium salt (binaphthylphosphonium hydrogen difluoride, 1 ) as an asymmetric catalyst for the asymmetric aldol reaction of benzaldehyde 2 and 2‐methyltetralone enol silyl ether 3 . In the search for an efficient catalyst, they prepared several catalysts carrying different R 1 and R 2 groups (R 1 =R 2 =H, Me, n‐ Bu and Bn).…”

Section: Previous Work (1997–2007)mentioning

confidence: 99%

Phosphonium Salts in Asymmetric Catalysis: A Journey in a Decade's Extensive Research Work

2017

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Use of Chiral Quaternary Salts in Asymmetric Synthesis

Cited by 19 publications

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

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

Chiral quaternary phosphonium salts as phase-transfer catalysts for environmentally benign asymmetric transformations

Phosphonium Salts in Asymmetric Catalysis: A Journey in a Decade's Extensive Research Work

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