Synthesis of α-<scp>d</scp>-galactose-based azacrown ethers and their application as enantioselective catalysts in Michael reactions

Rapi, Zsolt; Grűn, Alajos; Keglevich, György; Stirling, András; Bakó, Péter

doi:10.1039/c6nj02030e

Cited by 24 publications

(26 citation statements)

References 55 publications

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“…Absolute configuration was assigned by comparison of specific rotations with literature value. 26 The (+)-(R) enantiomer was formed in excess in every case.…”

Section: Application Of the Macrocycles In Asymmetric Synthesesmentioning

confidence: 98%

“…Michael addition of diethyl acetoxymalonate(10) to trans-chalcone(9) in the presence of mannitol-based crown ethers (isolation by preparative thin-layer chromatography (TLC). Absolute configuration was assigned by comparison of specific rotations with literature value 26. Absolute configuration was assigned by comparison of specific rotations with literature value 26.…”

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confidence: 99%

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Synthesis of d‐mannitol‐based crown ethers and their application as catalyst in asymmetric phase transfer reactions

et al. 2017

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A few new d-mannitol-based monoaza-15-crown-5 type chiral lariat ethers and 18-crown-6 type macrocycles were synthesized. These crown compounds were used as phase transfer catalysts in asymmetric Michael addititons and in a Darzens condensation under mild conditions to afford the corresponding products in a few cases in good to excellent enantioselectivities. In the Michael addition of diethyl acetoxymalonate to trans-chalcone, in the addition of diethyl acetamidomalonate to ß-nitrostyrene, in the reaction of diethyl bromomalonate with benzylidene malononitriles, in the cyclopropanation reaction of diethyl bromomalonate and 2-benzylidene-1,3-indandione, and in the Darzens condensation of α-chloroacetophenone with benzaldehyde, maximum enantioselectivities of 39%, 65%, 99%, 56%, and 62%, respectively, were obtained in the presence of the d-mannitol-based macrocycles as the catalysts.

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“…Absolute configuration was assigned by comparison of specific rotations with literature value. 26 The (+)-(R) enantiomer was formed in excess in every case.…”

Section: Application Of the Macrocycles In Asymmetric Synthesesmentioning

confidence: 98%

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confidence: 99%

Synthesis of d‐mannitol‐based crown ethers and their application as catalyst in asymmetric phase transfer reactions

et al. 2017

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“…The crude product was purified by preparative TLC using silica gel and hexane-EtOAc (10:1) as the eluent. The enantioselectivity was determined by 1 H NMR spectroscopy in the presence of Eu(hfc) 3 2.6 | General procedure for asymmetric model reactions using malonates [46][47][48] Unsaturated compound (1 mmol), substituted malonate (1.5 mmol) and the crown ether (0.15 mmol) were dissolved in a mixture of anhydrous THF (0.6 ml) and Et 2 O (2.4 ml) and dry Na 2 CO 3 (0.22 g, 2 mmol) was added. The reaction mixture was stirred at RT.…”

Section: General Procedures For Preparation Of Bisiodo Compoundsmentioning

confidence: 99%

Synthesis of l‐threitol‐based crown ethers and their application as enantioselective phase transfer catalyst in Michael additions

et al. 2017

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A few new l-threitol-based lariat ethers incorporating a monoaza-15-crown-5 unit were synthesized starting from diethyl l-tartrate. These macrocycles were used as phase transfer catalysts in asymmetric Michael addition reactions under mild conditions to afford the adducts in a few cases in good to excellent enantioselectivities. The addition of 2-nitropropane to trans-chalcone, and the reaction of diethyl acetamidomalonate with β-nitrostyrene resulted in the chiral Michael adducts in good enantioselectivities (90% and 95%, respectively). The substituents of chalcone had a significant impact on the yield and enantioselectivity in the reaction of diethyl acetoxymalonate. The highest enantiomeric excess (ee) values (99% ee) were measured in the case of 4-chloro- and 4-methoxychalcone. The phase transfer catalyzed cyclopropanation reaction of chalcone and benzylidene-malononitriles using diethyl bromomalonate as the nucleophile (MIRC reaction) was also developed. The corresponding chiral cyclopropane diesters were obtained in moderate to good (up to 99%) enantioselectivities in the presence of the threitol-based crown ethers.

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“…In our group, monoaza-15-crown-5-type lariat ethers incorporating a carbohydrate unit were synthesized [32,33]. These macrocycles generated high asymmetric induction in certain model reactions [34][35][36][37]. Although chiral crown compounds have been widely used as phase transfer catalysts, to the best of our knowledge, none of these catalysts were reusable.…”

Section: Introductionmentioning

confidence: 99%

The Synthesis of Hydrobenzoin-Based Monoaza Crown Ethers and Their Application as Recyclable Enantioselective Catalysts

et al. 2019

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New recyclable monoaza-15-crown ethers have been synthesized starting from (R,R)-(+)-and (S,S)-(−)-hydrobenzoin. These macrocycles proved to be efficient and reusable phase transfer catalysts in a few asymmetric reactions under mild conditions. The asymmetric epoxidation of trans-chalcone took place with up to 81% ee, while using other chalcone derivatives, the products were formed with 68-88% ee. The hydrobenzoin-based lariat ethers were also tested in the cyclopropanation of a few electron deficient olefins using diethyl bromomalonate to afford the product with good enantioselectivities (54-75% ee). The catalysts were recovered by salt formation, followed by extraction, and were reused without the loss of the activity and effect on the enantioselectivity.

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Synthesis of α-d-galactose-based azacrown ethers and their application as enantioselective catalysts in Michael reactions

Abstract: Crown ethers derived from d-galactose generated good to excellent enantioselectivities in a few Michael reactions under solid–liquid phase transfer conditions.

Cited by 24 publications

References 55 publications

Synthesis of d‐mannitol‐based crown ethers and their application as catalyst in asymmetric phase transfer reactions

Synthesis of d‐mannitol‐based crown ethers and their application as catalyst in asymmetric phase transfer reactions

Synthesis of l‐threitol‐based crown ethers and their application as enantioselective phase transfer catalyst in Michael additions

The Synthesis of Hydrobenzoin-Based Monoaza Crown Ethers and Their Application as Recyclable Enantioselective Catalysts

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