Trialkyl Phosphite Borines. A New Type of Phosphorus-boron Compound

Reetz, Theodor

doi:10.1021/ja01504a007

Cited by 42 publications

(10 citation statements)

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“…[16,17,34,35,36] The identity of the dominant acyloxyborohydride reducing species depends largely on the molar ratio between carboxylic acid and the borohydride, though exact determination of the dominant species is difficult. [16,17,[37][38][39] Generally, triacyloxyborohydrides are the most easily prepared and characterized, though other stable mono- [37,38] and diacyloxyborohy- dride [39] species have been reported. In our procedure, TarB-NO 2 and NaBH 4 are used in equimolar amounts, which would tend to favor the formation of a single monoacyloxyborohydride moiety per TarB-NO 2 molecule (Scheme 2).…”

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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“…Besides phosphorus, other heteroatom bearing functional groups also form dative bonds with BH 3 , depending on their property to act as a Lewis base. The following order of stability was suggested by displacement reactions: 36 Me 3 P-BH 3 , (Me 2 N) 3 P-BH 3 > Me 3 N-BH 3 > (RO) 3 P-BH 3…”

Section: Reaction Of Bh 3 With Phosphines Bearing Other Functional Grmentioning

confidence: 99%

Borane Complexes of Trivalent Organophosphorus Compounds. Versatile Precursors for the Synthesis of Chiral Phosphine Ligands for Asymmetric Catalysis

Ohff¹

1998

Synthesis

165

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In this review, the scope and limitations of BH 3 -protected trivalent organophosphorus compounds (phosphines, aminophosphines, phosphinites, etc.) as intermediates for the synthesis of chiral phosphines are discussed, representing a class of unique ligands for homogeneous asymmetric catalysis. Several applications of P-boranes are surveyed ranging from simple use as air-stable derivatives involved in facile purification procedures to versatile synthetic intermediates for highly stereoselective P-C and C-C coupling reactions. Relevant properties of P-boranes including the cleavage of the P-B bond are considered as well. Finally, several new pathways for the synthesis of chiral phosphine ligands are detailed. In selected examples, the efficiency of new ligands in asymmetric catalysis is briefly discussed.

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“…9 With this reagent system sec-phosphine oxides 1 reacted efficiently in THF solutions at 65°C and afforded phosphinous acidboranes 2 directly (Equation 3). Importantly, the competing formation of sec-phosphine-boranes was not observed under these conditions and prior conversions of sec-phosphine oxides into their anions were no longer necessary.…”

Section: Equationmentioning

confidence: 99%

Direct Conversion ofsec-Phosphine Oxides into Phosphinous Acid-Boranes

Stankevič¹,

Andrijewski²,

Pietrusiewicz³

2004

Synlett

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Two straightforward and general procedures for the synthesis of phosphinous acid-boranes directly from sec-phosphine oxides and borane reagents under basic and under neutral conditions have been developed. The conversion is stereoselective and occurs with predominant inversion of configuration at P. The protonation constants of a representative series of phosphinous acid-phosphinous acid-boranes have been determined.

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Trialkyl Phosphite Borines. A New Type of Phosphorus-boron Compound

Cited by 42 publications

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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

Borane Complexes of Trivalent Organophosphorus Compounds. Versatile Precursors for the Synthesis of Chiral Phosphine Ligands for Asymmetric Catalysis

Direct Conversion ofsec-Phosphine Oxides into Phosphinous Acid-Boranes

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Trialkyl Phosphite Borines. A New Type of Phosphorus-boron Compound

Cited by 42 publications

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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

Borane Complexes of Trivalent Organophosphorus Compounds. Versatile Precursors for the Synthesis of Chiral Phosphine Ligands for Asymmetric Catalysis

Direct Conversion ofsec-Phosphine Oxides into Phosphinous Acid-Boranes

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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