Chiral Modification of the Tetrakis(pentafluorophenyl)borate Anion with Myrtanyl Groups

Pommerening, Phillip; Oestreich, Martin

doi:10.1002/ejoc.201901434

Cited by 5 publications

(5 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1 H NMR (500 MHz, CDCl 3 ): major diastereoisomer: δ 0.70 (s, 3H), 1.20 (s, 4H), 1.57-1.62 (m, 1H), 1.86-1.93 (m, 3H), 2.24-2.06 (m, 1H), 2.36-2.39 (m, 1H), 2.52-2.55 (m, 1H), 2.72-2.75 (m, 1H), 9.75 (s, 1H); minor diastereoisomer: δ 0.88 (s, 3H), 1.25 (s, 4H), 1.68-1.77 (m, 1H), 1.82-1.88 (m, 3H), 2.09-2.13 (m, 2H), 2.26-2.30 (m, 1H), 2.75-2.80 (m, 1H), 9.59 (s, 1H). These data are consistent with those reported previously [38,39].…”

Section: -(T-butylphenylphosphinoyl)supporting

confidence: 94%

Myrtenal and Myrtanal as Auxiliaries in the Synthesis of Some C,P-Stereogenic Hydroxyphosphine Oxides and Hydroxyphosphine-Boranes Possessing up to Four Contiguous Centers of Chirality

et al. 2023

View full text Add to dashboard Cite

1,4- and 1,2-additons of secondary phosphine oxides to (1R)-myrtenal and (1S)-myrtanal were evaluated as potential routes to P,C-stereogenic phosphine oxides bearing additional hydroxyl or aldehyde functions. 1,4-Additions of racemic secondary phosphine oxides to (1R)-myrtenal were found to offer moderate to good stereoselectivity which shows some promise for utility in kinetic resolution processes, especially at lower conversions. In case of 1,2-additions making the process doubly asymmetric by using an enantiomerically pure secondary phosphine oxide as substrate turned out to be practical. The stereochemical course of the addition reactions under study is presented. The P-resolved 1,2-addition products were demonstrated to undergo facile reduction by BH3 at room temperature leading to the formation of the corresponding α-hydroxyphosphine-boranes with clean inversion of configuration at the P-centre. All P,C-stereogenic phosphine oxides and boranes that were isolated in the form of a single diastereoisomer were assigned their absolute configurations by means of X-ray crystallography and/or 2D NMR spectral techniques.

show abstract

Section: -(T-butylphenylphosphinoyl)supporting

confidence: 94%

Myrtenal and Myrtanal as Auxiliaries in the Synthesis of Some C,P-Stereogenic Hydroxyphosphine Oxides and Hydroxyphosphine-Boranes Possessing up to Four Contiguous Centers of Chirality

et al. 2023

View full text Add to dashboard Cite

show abstract

“…To maintain the exceptional Lewis acidity of the silylium ion catalyst, the design and synthesis of chiral weakly coordinating anions is needed. 463,464 In an effort to Scheme 125 465 While chiral borate 397 − was stable in the presence of in situ-generated silylcarboxonium ion 398 + , the subsequent cycloaddition with cyclohexa-1,3-diene (340) proceeded smoothly but with no enantioinduction (Scheme 128, bottom). The (Mukaiyama) aldol reaction is a valuable C−C bond formation reaction, for which the tetracoordinate silicon Lewis acids Me 3 SiOTf 466−468 and Me 3 SiNTf 2 469 have been shown to be efficient catalysts.…”

Section: Silylium-ion-catalyzed Diels−alder Reactionsmentioning

confidence: 99%

“…The lower reactivity is likely to be ascribed to the higher nucleophilicity of the corresponding anion [( S , S )- 387a ] − compared to [B(C 6 F 5 ) 4 ] − . To maintain the exceptional Lewis acidity of the silylium ion catalyst, the design and synthesis of chiral weakly coordinating anions is needed. , In an effort to address this goal, Pommerening and Oestreich prepared a chiral version of [B(C 6 F 5 ) 4 ] − , in which the para -fluorine atoms were replaced by the myrtanyl group (Scheme , top) . While chiral borate 397 – was stable in the presence of in situ-generated silylcarboxonium ion 398 + , the subsequent cycloaddition with cyclohexa-1,3-diene ( 340 ) proceeded smoothly but with no enantioinduction (Scheme , bottom).…”

Section: Applications Of Silylium Ions In Synthesis and Catalysismentioning

confidence: 99%

Silylium Ions: From Elusive Reactive Intermediates to Potent Catalysts

et al. 2021

Self Cite

View full text Add to dashboard Cite

The history of silyl cations has all the makings of a drama but with a happy ending. Being considered reactive intermediates impossible to isolate in the condensed phase for decades, their actual characterization in solution and later in solid state did only fuel the discussion about their existence and initially created a lot of controversy. This perception has completely changed today, and silyl cations and their donor-stabilized congeners are now widely accepted compounds with promising use in synthetic chemistry. This review provides a comprehensive summary of the fundamental facts and principles of the chemistry of silyl cations, including reliable ways of their preparation as well as their physical and chemical properties. The striking features of silyl cations are their enormous electrophilicity and as such reactivity as super Lewis acids as well as fluorophilicity. Known applications rely on silyl cations as reactants, stoichiometric reagents, and promoters where the reaction success is based on their steady regeneration over the course of the reaction. Silyl cations can even be discrete catalysts, thereby opening the next chapter of their way into the toolbox of synthetic methodology.

show abstract

“…However, the presence of coordinating oxygen- and nitrogen-donor atoms in these nonsuperacids makes them incompatible with truly “superelectrophile conditions”. Attempts with weakly coordinating anions on the basis of perfluorinated borate anions have not been fruitful so far, − and Brønsted acids with chiral carborate anions have not been described yet.…”

Section: Concluding Remarks and Outlookmentioning

confidence: 99%

The Power of the Proton: From Superacidic Media to Superelectrophile Catalysis

Klare

Oestreich

2021

J. Am. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

Superacidic media became famous in connection with carbocations. Yet not all reactive intermediates can be generated, characterized, and eventually isolated from these Brønsted acid/Lewis acid cocktails. The counteranion, that is the conjugate base, in these systems is often too nucleophilic and/or engages in redox chemistry with the newly formed cation. The Brønsted acidity, especially superacidity, is in fact often not even crucial unless protonation of extremely weak bases needs to be achieved. Instead, it is the chemical robustness of the aforementioned counteranion that determines the success of the protolysis. The advent of molecular Brønsted superacids derived from weakly coordinating, redox-inactive counteranions that do withstand the enormous reactivity of superelectrophiles such as silicon cations completely changed the whole field. This Perspective summarizes general aspects of medium and molecular Brønsted acidity and shows how applications of molecular Brønsted superacids have advanced from stoichiometric reactions to catalytic processes involving protons and in situ generated superelectrophiles.

show abstract

Chiral Modification of the Tetrakis(pentafluorophenyl)borate Anion with Myrtanyl Groups

Cited by 5 publications

References 48 publications

Myrtenal and Myrtanal as Auxiliaries in the Synthesis of Some C,P-Stereogenic Hydroxyphosphine Oxides and Hydroxyphosphine-Boranes Possessing up to Four Contiguous Centers of Chirality

Myrtenal and Myrtanal as Auxiliaries in the Synthesis of Some C,P-Stereogenic Hydroxyphosphine Oxides and Hydroxyphosphine-Boranes Possessing up to Four Contiguous Centers of Chirality

Silylium Ions: From Elusive Reactive Intermediates to Potent Catalysts

The Power of the Proton: From Superacidic Media to Superelectrophile Catalysis

Contact Info

Product

Resources

About