Enantioselective Deprotonation as a Vehicle for the Asymmetric Synthesis of C2-Symmetric P-Chiral Diphosphines

Muci, Alexander R.; Campos, Kevin R.; Evans, David A.

doi:10.1021/ja00140a028

Cited by 276 publications

(186 citation statements)

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“…The method has also been applied to N-Bocpyrrolidines, [10,11] several benzylic substrates, [12] ferrocenes, [13] P,P-dimethylarylphosphane derivatives, [14] as well as to the kinetic resolution of a racemic allyl carbamate [15] and of several b-stereogenic alkyl carbamates. [16] Moreover, a desymmetrization of meso-oxabicycles by alkyllithium/(À)-sparteine-induced ring-opening has been described by Lautens et al [17] and Hodgson et al [18] The (À)-sparteine-induced deprotonation of alkyl carbamates 3 generated from primary alcohols, which bear nonmesomerically stabilizing groups adjacent to the carbanionic center in 5, is characterized by a pronounced pro-S selectivity in the deprotonation step.…”

Section: Introductionmentioning

confidence: 99%

Efficient Desymmetrization ofmeso-cis-1,2-Cyclohexanedimethanol with Differentiation between Diastereotopic and Enantiotopic C−H Bonds by (−)-Sparteine-Mediated Deprotonation

et al. 1999

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The deprotonation of a dicarbamate prepared from cis-1,2-cyclohexanedimethanol by sec-butyllithium/(À)-sparteine proceeds with efficient selection between the enantiotopic branches and their diastereotopic protons with high preference for the pro-S proton at the R branch to afford the intermediate, configurationally stable lithium compound as a single diastereomer. Trapping of this intermediate by electrophiles (DOMe, CO 2 , CH 3 I, Me 3 SiCl, or R 3 SnCl) takes place with retention of the configuration to yield highly enantiomerically and diastereomerically enriched substitution products, which are easily converted to diols, to anellated tetrahydrofurans, or to g-lactones. The chiral base is also capable of efficient kinetic resolution of the racemic adeuterated starting material, by the utilization of an extraordinarily high kinetic H/D isotope effect within the deprotonation step. The, presumably, first example of the kinetic resolution of a racemic stannane by lithiodestannylation, utilizing methyllithium/(À)-sparteine, is reported.

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Section: Introductionmentioning

confidence: 99%

Efficient Desymmetrization ofmeso-cis-1,2-Cyclohexanedimethanol with Differentiation between Diastereotopic and Enantiotopic C−H Bonds by (−)-Sparteine-Mediated Deprotonation

et al. 1999

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“…The yields were satisfactory-to-high in all experiments and the products obtained were generally white crystalline solids. Although we have analysed the products as the phosphaneϪborane complexes, decomplexation to the free phosphane can be effected using amines [4,18] or treatment with acid followed by hydrolysis. [6,19] …”

Section: Resultsmentioning

confidence: 99%

“…[3] An elegant approach involving the enantioselective deprotonation of prochiral dimethylphosphaneϪboranes with a (Ϫ)-sparteine·butyllithium complex has been developed by Evans, [4] while Livinghouse has reported a related study concerning the dynamic resolution of lithiated racemic tert-butylphenylphosphaneϪborane. [5] Imamoto has applied the enantioselective deprotonation approach both to the preparation of the BisP* [6] and MiniPHOS [7] ligands, while Zhang et al have again shown the elegance of the (Ϫ)-sparteine·butyllithium method in their synthesis of Tangphos.…”

Section: Introductionmentioning

confidence: 99%

Desymmetrization of Prochiral Phosphanes Using Derivatives of (−)‐Cytisine

et al. 2004

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Historically, (−)‐sparteine·sec‐BuLi has been used to desymmetrize prochiral phosphanes. In this report, derivatives of an alkaloid extracted from the seeds of Laburnum anagyroides have been utilized to mimic (+)‐sparteine, which is not readily available. In several cases, the enantioselectivities achieved with the (+)‐sparteine surrogates outperformed (−)‐sparteine itself in the deprotonation of alkyl‐substituted (as well as aryl‐substituted) prochiral phosphane derivatives. In addition, use of these surrogates allows a new methodology for a chiral switch in phosphorus chemistry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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“…Trichlorophosphine was converted into alkyldimethylphosphine-boranes (12) in one pot, and these, in turn, were subjected to enantioselective deprotonation with s-BuLi/(-)-sparteine in ether. 13 The resulting enantiomerically enriched organolithium compounds (13) were oxidatively dimerized on treatment with CuCl2 to give compounds 14 in good yields. Subsequent removal of the boranato groups by the reaction with amine was unsuccessful, but it was accomplished by using the method developed by McKinstry and Livinghouse.…”

Section: Optically Pure 12-bis [(O-alkylphenyl)phenylphosphino] -Ethmentioning

confidence: 99%

P-Chiral Phosphine Ligands for Transition-Metal-Catalyzed Asymmetric Reactions

Imamoto

2007

J. Syn. Org. Chem., Jpn.

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: Optically active phosphine ligands possessing stereogenic centers on phosphorus atoms have been synthesized using phosphine-boranes as intermediates. Electron-rich P-chiral phosphine ligands (BisP*, MiniPHOS, and DiSquareP*) having a bulky alkyl group and a small alkyl group on the phosphorus atom exhibit excellent to almost perfect enantioselectivities in the Rh-catalyzed asymmetric hydrogenation of enamides and related substrates. Air-stable P-chiral phosphine ligands (t-Bu-and 1-Ad-QuinoxP*) are also prepared with the phosphine-borane methodology. These ligands have exceedingly high enantioselectivities of up to 99.9% not only in Rh-catalyzed asymmetric hydrogenation but also in Rh-or Pd-catalyzed carbon-carbon bond-forming reactions.Catalytic asymmetric synthesis is one of the most efficient methods for the production of optically active compounds. Among various asymmetric catalyses, transition-metal-catalyzed reactions have attracted a great deal of attention over the years; many catalyst systems of this class have been developed and some have been successfully applied to the industrial production of useful optically active compounds.1 Both enantioselectivity and catalytic efficiency are highly dependent on chiral ligands and central metals. Therefore, the design and synthesis of new chiral ligands is a very important research subject in this field.2Among various types of chiral ligands, phosphine ligands are the most frequently employed, owing to their inherent ability to coordinate strongly to transition metals and to promote catalytic reactions. Hence, numerous optically active phosphine ligands have been synthesized and used in tiansition metal catalyses.3 Chiral phosphine ligands reported so far are classified roughly into two types. One type is phosphines having asymmetric carbon atoms or backbone chirality. Representative examples of this type are shown in Figure 1. The stereochemical feature of this type is that the two substituents on the phosphorus atoms are diastereotopic and are capable of forming an asymmetric environment around the reaction center.The other type is the so-called P-chiral phosphine ligands, that possess stereogenic centers on the phosphorus atoms themselves. Figure 2 shows methylphenylpropylphosphine (1),4a,b CAMP (2),4c and DIPAMP (3),4d-g which are representative P-chiral phosphine ligands. These ligands played very important roles early on in the history of homogeneous asymmetric hydrogenation.4 Nevertheless, only a small number of P-chiral ligands were reported in the two decades following 1976, mainly because of the lack of efficient methods for the preparation of optically pure P-chiral phosphines, and the anticipation that some phosphines of this class are stereochemically unstable and gradually racemize via pyramidal inversion even at room temperature.5CAMP (2) DIPAMP (3) In a previous study of the synthesis and reactions of phosphine-boranes, we found that optically active P-chiral phosphine ligands could be synthesized using phosphine-boranes as intermediat...

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Enantioselective Deprotonation as a Vehicle for the Asymmetric Synthesis of C2-Symmetric P-Chiral Diphosphines

Abstract: Chiral diphosphines1 are the ligands of choice for a wide range of enantioselective transition-metal-catalyzed processes.2 While chirality may be independently incorporated on either

Cited by 276 publications

References 1 publication

Efficient Desymmetrization ofmeso-cis-1,2-Cyclohexanedimethanol with Differentiation between Diastereotopic and Enantiotopic C−H Bonds by (−)-Sparteine-Mediated Deprotonation

Efficient Desymmetrization ofmeso-cis-1,2-Cyclohexanedimethanol with Differentiation between Diastereotopic and Enantiotopic C−H Bonds by (−)-Sparteine-Mediated Deprotonation

Desymmetrization of Prochiral Phosphanes Using Derivatives of (−)‐Cytisine

P-Chiral Phosphine Ligands for Transition-Metal-Catalyzed Asymmetric Reactions

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