Memory of Chirality Approach to the Enantiodivergent Synthesis of Chiral Benzo[<i>d</i>]sultams

Foschi, Francesca; Tagliabue, Aaron; Mihali, Voichiţa; Pilati, Tullio; Pecnikaj, Ilir; Penso, Michele

doi:10.1021/ol401557v

Cited by 28 publications

(18 citation statements)

References 33 publications

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“…[17][18][19][20][21][22]34] Theo nly method currently available for the asymmetric arylation of amino acids with electron-rich rings requires stoichiometric [g] Attempted rearrangement of 7 returned acomplex mixture of products. [17][18][19][20][21][22]34] Theo nly method currently available for the asymmetric arylation of amino acids with electron-rich rings requires stoichiometric [g] Attempted rearrangement of 7 returned acomplex mixture of products.…”

Section: Methodsmentioning

confidence: 99%

“…[2] Ar ange of methods for the asymmetric a-alkylation of readily available amino acids makes simple quaternary amino acids bearing a-alkyl groups readily accessible. [16] Electron-deficient rings may be introduced intra- [17][18][19][20] or intermolecularly [21][22][23] by stereoselective aryne or S N Ar chemistry.Maruoka et al [24] achieved an asymmetric phase-transfer arylation with Cr complexes of electron-rich arenes.We previously reported [25] ar acemic approach to the synthesis of a-aryl amino acids that makes use of the rearrangement of N-aryl urea derivatives [26][27][28][29][30] of amino acid enolates with migration of an aromatic ring from NtoC.The reaction formally involves an intramolecular nucleophilic aromatic substitution reaction, [31,32] but is much more general with regard to ring electronics than atypical S N Ar reaction. [16] Electron-deficient rings may be introduced intra- [17][18][19][20] or intermolecularly [21][22][23] by stereoselective aryne or S N Ar chemistry.Maruoka et al [24] achieved an asymmetric phase-transfer arylation with Cr complexes of electron-rich arenes.…”

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confidence: 99%

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confidence: 99%

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Pseudoephedrine‐Directed Asymmetric α‐Arylation of α‐Amino Acid Derivatives

Atkinson¹,

Fernández‐Nieto²,

Roselló³

et al. 2015

Angew Chem Int Ed

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Available α-amino acids undergo arylation at their α position in an enantioselective manner on treatment with base of N'-aryl urea derivatives ligated to pseudoephedrine as a chiral auxiliary. In situ silylation and enolization induces diastereoselective migration of the N'-aryl group to the α position of the amino acid, followed by ring closure to a hydantoin with concomitant explulsion of the recyclable auxiliary. The hydrolysis of the hydantoin products provides derivatives of quaternary amino acids. The arylation avoids the use of heavy-metal additives, and is successful with a range of amino acids and with aryl rings of varying electronic character.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Pseudoephedrine‐Directed Asymmetric α‐Arylation of α‐Amino Acid Derivatives

Atkinson¹,

Fernández‐Nieto²,

Roselló³

et al. 2015

Angew Chem Int Ed

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“…A series of highly substituted five‐membered chiral benzosultams was prepared through base‐promoted intramolecular S N Ar of chiral aryl sulfonamides 46.1 with high enantiomeric excesses (Scheme ) . The configurations of the obtained sultams depended on the reaction conditions.…”

Section: Metal‐free Synthesis Of Sultamsmentioning

confidence: 99%

Sultams: Recent Syntheses and Applications

Debnath¹,

Mondal²

2018

Eur J Org Chem

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Sultams are very important scaffolds both in medicinal chemistry and in synthetic organic chemistry. Very important methodologies for the asymmetric and non‐asymmetric synthesis of sultams, including asymmetric synthesis with memory of chirality (MOC), have recently been developed. Nowadays sultams are tremendously widely applied both in the medicinal field and in the synthetic field for the synthesis of different natural and non‐natural heterocycles. This review covers the recent development (2011–June 2017) of powerful methodologies for the synthesis of sultams and their applications in various fields during this period. A critical view of the mechanisms of the developed methodologies together with the scope and limitations of these methods add an extra dimension to the text.

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“…The asymmetric synthesis proceeds via the transient chiral species with limited half-lives of racemization. [1][2][3][4][5][6][7][8][9][10][11][12][13] We have developed strategy for asymmetric induction via enolate intermediate A with a chiral C-C axis in 1991 1) (Chart 1, Eq. 1).…”

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confidence: 99%

Asymmetric Synthesis of Multisubstituted Dihydrobenzofurans by Intramolecular Conjugate Addition of Short-Lived C–O Axially Chiral Enolates

Tomohara

Kasamatsu

Yoshimura

et al. 2016

CHEMICAL & PHARMACEUTICAL BULLETIN

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Enantioselective intramolecular conjugate addition reactions of short-lived C-O axially chiral enolates have been developed. The reactions proceeded with inversion of the configuration and provided dihydrobenzofurans with contiguous tetra-and trisubstituted carbon centers in up to 96% enantiomeric excess (ee).Key words axially chiral enolate; asymmetric synthesis; chiral C-O axis; dihydrobenzofuran; conjugate addition; restricted bond rotation Asymmetric synthesis had been classified into three categories: 1) optical resolution of the racemate by diastereomer formation, 2) diastereoselective synthesis using chiral auxiliaries, and 3) enantioselective synthesis using chiral catalysts or chiral reagents. On the other hand, we have studied asymmetric reactions that proceed via enolate intermediates with intrinsic axial chirality (MOC: memory of chirality).1-6) This strategy does not belong to any of above three categories. We believe that MOC strategy created the forth category of asymmetric synthesis. The characteristic feature of the asymmetric reactions based on MOC strategy is asymmetric reactions take place at the original stereogenic center of the starting material in the absence of external chiral sources. Accordingly, when the optically active starting materials are abundant and ubiquitous α-amino acids, asymmetric synthesis based on MOC strategy is especially advantageous. MOC strategy also has salient feature in the mechanistic point of view. The asymmetric synthesis proceeds via the transient chiral species with limited half-lives of racemization. [1][2][3][4][5][6][7][8][9][10][11][12][13] We have developed strategy for asymmetric induction via enolate intermediate A with a chiral C-C axis in 1991 1) (Chart 1, Eq. 1). The half-life of racemization of the axially chiral enolate A at the reaction temperature (−20°C) was estimated to be ca. 24 d. 1) We then developed a method for asymmetric induction via enolate intermediate B with a chiral C-N axis in 20002) (Chart 1, Eq. 2). The half-life of racemization of the axially chiral enolate B was determined to be 22 h at the reaction temperature (−78°C) by the measurement of the time-dependent racemization of enolate B. As logical possibility, the asymmetric induction might take place via configurationally stable carbanion B′ (Chart 1, Eq. 4). However, this possibility was eliminated because diBoc derivative 2a (>99% enantiomeric excess (ee)) gave the racemic product by the same treatment for 2 (Chart 1, Eq. 5). Since the enolate B″ generated from 2a cannot to be axially chiral along the C-N axis even through rotation of the C-N bond is restricted, racemate formation is a reasonable consequence. We finally succeeded to develop asymmetric synthesis via short-lived C-O axially chiral enolates with the supposed half-life of racemization as short as ca. 1 s at −78°C 6) (Chart 1, Eq. 3). The reaction shown in Eq. 3 was the first example of asymmetric reaction that proceeds via an axially chiral enolate with the restricted rotation of the C-O axis as the sole source ...

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Memory of Chirality Approach to the Enantiodivergent Synthesis of Chiral Benzo[d]sultams

Cited by 28 publications

References 33 publications

Pseudoephedrine‐Directed Asymmetric α‐Arylation of α‐Amino Acid Derivatives

Pseudoephedrine‐Directed Asymmetric α‐Arylation of α‐Amino Acid Derivatives

Sultams: Recent Syntheses and Applications

Asymmetric Synthesis of Multisubstituted Dihydrobenzofurans by Intramolecular Conjugate Addition of Short-Lived C–O Axially Chiral Enolates

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