Asymmetric reduction of cyclic imines with chiral sodium acyloxyborohydrides

Yamada, Kazuo; Takeda, Mikio; Iwakuma, Takeo

doi:10.1039/p19830000265

Cited by 80 publications

(30 citation statements)

References 3 publications

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“…[7,12,22,33] An explanation lies in the solubility of the active reducing species. In a homogeneous system, both chirally modified and unmodified achiral sodium borohydride may compete for the ketone substrate.…”

Section: Resultsmentioning

confidence: 99%

Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH₄ and TarB‐NO₂: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System

et al. 2005

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High enantioselectivities are obtained for the reduction of a series of ketones using the inexpensive and mild reducing agent NaBH4 with TarB‐NO2 (1). This easily prepared tartaric acid‐based reagent combines a Lewis acid with carboxylic acids in a single bifunctional reagent. When combined with NaBH4, the resulting chiral acyloxyborohydride mediates the reduction of aromatic ketones to provide the product alcohols in enantiomeric excesses of 93–98 %. Several aliphatic ketones were also reduced with moderate to excellent enantioselectivity. A unique mechanism is provided with supporting calculations for the proposed active species and transition state. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Section: Resultsmentioning

confidence: 99%

Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH₄ and TarB‐NO₂: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System

et al. 2005

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“…The ratio of 93:7 ( 18A / 18B ) is in good accordance with the calculated ratio of the diastereomeric iminium salts 17D and 17A (146:7), and this supports the discussed pathway. It is known that TFA and NaBH 4 form trifluoroacetoxyborohydride species in THF,31,32 so these are the probable reducing agents in this reaction. The enammonium salt 17B is more stable than the iminium salt 17D by 12.2 kJ mol –1 ; however, initially formed enammonium species are known to undergo H‐shift towards the iminium tautomer 33…”

Section: Resultsmentioning

confidence: 99%

Stereoselective Synthesis of cis,cis‐Configured Vicinal Triamines

Schulte¹,

Saitō²,

Wünsch³

2014

Eur J Org Chem

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The first stereoselective synthesis of a cis,cis‐configured vicinal triamine was achieved, starting from N‐cyclohexenylpyrrolidone (10). The reaction sequence consists of the stereoselective construction of the trans‐configured 1,3‐diamide 14, trans‐to‐cis isomerization via enols or enamines, and subsequent highly stereoselective reduction of the intermediate imine 17D to the amine 18A. The postulated reaction pathway explains the observed stereoconvergence and is supported by calculation of the heats of formation of its intermediates at the PM3 level. LiAlH4 reduction of 18A yielded the tetracyclic aminal 19, which was converted into the pyrrolidinylquinoxaline 7, which showed low to moderate affinity towards κ and σ1 receptors.

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“…In our hands usual cleavage of the N-borane adduct 7 as described 9) does not give any defined product. Therefore, we used our work-up procedure with simultaneous N-acylation 4 ' 10) , leading to the rotamers of (+)-(R)-N-formylnornicotine (CH3CO)20…”

Section: Enantioselektive Synthese Einiger Nicotiana-alkaloidementioning

confidence: 99%

“…Chiral reductions of imines being part of indol and isoquinoline alkaloids with Iwakuma's reagent 9) are known. In our hands usual cleavage of the N-borane adduct 7 as described 9) does not give any defined product.…”

Section: Enantioselektive Synthese Einiger Nicotiana-alkaloidementioning

confidence: 99%

Enantioselective Synthesis of Some Nicotiana Alkaloids

Mahboobi

Wiegrebe

1988

Archiv der Pharmazie

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A modified approach to myosmine (6) via a silyl enol ether of 3-acetylpyridine (1) is described. Chiral reduction of 6 with A^-(benzyloxycarbonyl)-Lproline/NaBH 4 and formylation leads to (JR)-A r -formylnornicotine (8) (35 % ee) which in turn is converted to (Ä)-nornicotine (11) and ^nico-tine (10). Enantioselektive Synthese einiger Nicotiana-AlkaloideWir beschreiben eine modifizierte Synthese des Myosmins (6)

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Asymmetric reduction of cyclic imines with chiral sodium acyloxyborohydrides

Cited by 80 publications

References 3 publications

Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH₄ and TarB‐NO₂: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System

Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH₄ and TarB‐NO₂: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System

Stereoselective Synthesis of cis,cis‐Configured Vicinal Triamines

Enantioselective Synthesis of Some Nicotiana Alkaloids

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Asymmetric reduction of cyclic imines with chiral sodium acyloxyborohydrides

Cited by 80 publications

References 3 publications

Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH4 and TarB‐NO2: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System

Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH4 and TarB‐NO2: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System

Stereoselective Synthesis of cis,cis‐Configured Vicinal Triamines

Enantioselective Synthesis of Some Nicotiana Alkaloids

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Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH₄ and TarB‐NO₂: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System

Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH₄ and TarB‐NO₂: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System