Synthesis and Application of P-Stereogenic Phosphines as Superior Reagents in the Asymmetric Aza-Wittig Reaction
摘要:
[GRAPHICS]A wide variety of P-stereogenic aryldialkylphosphines were prepared in enantioenriched form by a systematic diversification of the (-)-sparteine-mediated dynamic kinetic resolution of racemic lithiophosphine-boranes reported by Livinghouse. Excellent asymmetric induction was observed provided that the intermediate lithiophosphine/sparteine complex precipitated from solution; more soluble derivatives returned poor ee's or racemic material. The resulting phosphine-boranes were deprotected and used as reagents in the desymmetrizing asymmetric aza-Wittig reaction of 2-alkyl-2-(3-azidopropyl)cyclohexane-1,3-diones, delivering the highest ee's yet observed in this process (up to 84% ee). Phosphines bearing bulky substituents required heating for the aza-Wittig reaction to proceed to completion, which P-31 NMR studies showed to be due to interception of the reaction by the formation of unreactive (E)-phosphazides. This was circumvented by use of methyltrioxorhenium to catalyze the formation of iminophosphoranes from the azide and phosphine, allowing reactions to take place at ambient temperature, although the ee's of the asymmetric reactions were reduced in these examples.
Reactivity of chiral oxazaphospholidines on activated halide compounds: Synthesis and coordination studies of chiral hybrid phosphine-phosphine oxide ligands
作者:Bruno Faure、Olivier Pardigon、Gérard Buono
DOI:10.1016/s0040-4020(97)00749-7
日期:1997.8
and a mixture of diastereomers 6:7 as the Perkow products. New hybrid phosphine-phosphineoxideligands were easily obtained from phosphinamides 3, bearing chirality on the carbon chain and the phosphine oxide moiety (BPPO), or on the carbon chain and the two different phosphorus centers (8 and 9). The coordination chemistry of ligand BPPO has been studied, with transition metals and Lewis Acids.
An Expedient Reduction of<i>sec</i>-Phosphine Oxides to<i>sec</i>-Phosphine-boranesby BH<sub>3</sub>˙SMe<sub>2</sub>
作者:K. Michał Pietrusiewicz、Marek Stankevič
DOI:10.1055/s-2003-39304
日期:——
Secondary phosphine oxides can be expeditiously converted into secondary phosphine-boranes by treatment with an excess of BH3ËSMe2 at room temperature. Selectivity of the conversion towards the formation of secondary phosphine-boranes is greatly improved by the addition of a small amount of water to the reaction mixture.
Regio- and Stereoselective Hydrophosphination Reactions of Alkynes with Phosphine−Boranes: Access to Stereodefined Vinylphosphine Derivatives
作者:David Mimeau、Annie-Claude Gaumont
DOI:10.1021/jo030096q
日期:2003.9.1
Vinylphosphine-borane complexes are easily synthesized by regio- and stereoselective hydrophosphination of terminal alkynes with use of secondary phosphine-boranes as hydrophosphinating agent. The regioselectivity of the reaction is efficiently controlled by the choice of the activation process: thermal or metal catalyst activation. The vinylphosphine derivatives are purified by chromatography on silica
The Synthesis and Reactivity of Phosphinous Acid-Boranes
作者:K. Michał Pietrusiewicz、Marek Stankevič
DOI:10.1055/s-2005-861878
日期:——
Phosphinic acid chlorides are converted directly into phosphinous acid-boranes in a process utilizing BH 3 .THF complex as a reducing agent. The process is general and affords phosphinous acid-boranes in good to very high yields. Phosphinous acid-boranes have been found to react readily with alkylating, acylating, reducing, halogenating and deborating agents to produce the corresponding phosphinous acid-borane
complexes are easily synthesized by palladium-catalyzed C−P cross-coupling of vinyltriflates with secondary phosphine−boranes. This method allows the synthesis of phosphine derivatives not always easily accessible by other approaches. The vinylphosphine derivatives are purified by chromatography on silica gel. The versatility of the method is proved by using various triflates and diaryl-, dialkyl- and al