Preparation of a Privileged Silicon‐Stereogenic Silane: Classical <i>versus</i> Kinetic Resolution

Rendler, Sebastian; Auer, Gertrud; Keller, Manfred; Oestreich, Martin

doi:10.1002/adsc.200606071

Cited by 101 publications

(74 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…On that occasion, we became aware that a similar level of stereoselection was obtained when priveleged cyclic system 1a [11] was exchanged for the important acyclic congener 1b [12-15] (Figure 1). We had erroneously missed this known tertiary silane.…”

Section: Resultsmentioning

confidence: 82%

Conformational rigidity of silicon-stereogenic silanes in asymmetric catalysis: A comparative study

Rendler¹,

Oestreich²

2007

Beilstein J. Org. Chem.

Self Cite

View full text Add to dashboard Cite

In recent years, cyclic silicon-stereogenic silanes were successfully employed as stereoinducers in transition metal-catalyzed asymmetric transformations as exemplified by (1) the hydrosilylation of alkenes constituting a chirality transfer from silicon to carbon and (2) the kinetic resolution of racemic mixtures of alcohols by dehydrogenative silicon-oxygen coupling. In this investigation, a cyclic and a structurally related acyclic silane with silicon-centered chirality were compared using the above-mentioned model reactions. The stereochemical outcome of these pairs of reactions was correlated with and rationalized by the current mechanistic pictures. An acyclic silicon-stereogenic silane is also capable of inducing excellent chirality transfer (ct) in a palladium-catalyzed intermolecular carbon-silicon bond formation yet silicon incorporated into a cyclic framework is required in the copper-catalyzed silicon-oxygen bond forming reaction.Page 1 of (page number not for citation purposes) FindingsWithin the last decade, several asymmetric transformations based on silicon-stereogenic reagents or substrates were revisited or invented. [1][2][3][4] Aside from the use of silicon-stereogenic chiral auxiliaries in substrate-controlled reactions, [5] a still limited number of remarkable stereoselective processes with a stereogenic silicon as the reactive site were reported, [6] namely the inter- [7] as well as intramolecular [8] chirality transfers from silicon to carbon. Moreover, we had demonstrated that chiral silanes resolve racemic mixtures of alcohols in a non-enzymatic, transition metal-catalyzed kinetic resolution. [9] During our ongoing investigations directed towards the mechanistic elucidation of the origin of the chirality transfer in a palladium-catalyzed hydrosilylation, [10] we had to perform an extensive screening of silicon-stereogenic tertiary silanes. On that occasion, we became aware that a similar level of stereoselection was obtained when priveleged cyclic system 1a [11] Beilstein Journal of Organic Chemistry 2007, 3, No. 9. Page 2 of (page number not for citation purposes) 5Scheme 1: Cyclic and acyclic chiral silanes as potent reagents for the silicon-to-carbon chirality transfer. was exchanged for the important acyclic congener 1b [12][13][14][15] ( Figure 1). We had erroneously missed this known tertiary silane. This was particularly unfortunate in the light of the fact that these silanes are both decorated with three substituents of different steric demand and, therefore, display marked stereochemical differentiation around silicon.In this preliminary communication, we wish to report a comparison of cyclic 1a and acyclic 1b as stereoinducers in the palladium-catalyzed chirality transfer from silicon to carbon and in the copper-catalyzed kinetic resolution of donor-functionalized alcohols capable of two-point binding.The reagent-controlled hydrosilylation of norbornene derivative 2 with silane 1a proceeds with a perfect chirality transfer (rac-1a → rac-3a, Scheme 1).[8] Mechanistic ...

show abstract

Section: Resultsmentioning

confidence: 82%

Conformational rigidity of silicon-stereogenic silanes in asymmetric catalysis: A comparative study

Rendler¹,

Oestreich²

2007

Beilstein J. Org. Chem.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Eine einfache Variation der Liganden und des Metall/Ligand-Verhältnisses [15] wurde durch Verwendung des Präkatalysators [Rh(cod) 2 ]OTf sichergestellt. Um diese Rhodium-Ligand-Kombinationen zu testen (Tabelle 1), wählten wir die Reaktion des privilegierten [16] Silans rac-1 [17] mit dem donorfunktionalisierten Alkohol rac-2 aus, der sich bereits in unserer früheren Studie als gutes Substrat erwiesen hatte. [6] Da dieser Prozess von Natur aus diastereoselektiv ist, wird das Diastereomerenverhältnis des Silylethers 3 direkt mit dem Selektivitätsfaktor der dazugehörigen kinetischen Racematspaltung korrelieren; daher wurden diese Katalysatorsysteme mit racemischem Silan bewertet.…”

unclassified

“…Die Steigung (= Selektivitätsfaktor) der erhaltenen Geraden ist näherungsweise 900. [19] Um diesen außerge-wöhnlichen Befund zu bekräftigen, bestimmten wir zudem den Enantiomerenüberschuss des schnell reagierenden Enantiomers (S)-2 nach stereospezifischer reduktiver Spaltung [6,17] von diastereomerenangereichertem ( Si S,S)-3 (d.r. % 96:4 bei 51 % Umsatz).…”

unclassified

Chirale Erkennung mit siliciumstereogenen Silanen: außergewöhnliche Selektivitätsfaktoren bei der kinetischen Racematspaltung von donorfunktionalisierten Alkoholen

Klare

Oestreich

2007

Angewandte Chemie

Self Cite

View full text Add to dashboard Cite

“…21 This led us to carefully reinvestigate a variant that had proven fruitless in the past. 21 Hindered trichlorosilanes 9 were used directly in the above-mentioned Grignard reaction with 6 19 (9 → rac-4, Scheme 4).…”

Section: Preparation Of Silicon-stereogenic Silanesmentioning

confidence: 99%

Silicon-Stereogenic Silanes in Asymmetric Catalysis

Oestreich¹

2007

Synlett

Self Cite

180

View full text Add to dashboard Cite

The exploitation of chirality at silicon in asymmetric catalysis is a challenging task. Silicon-stereogenic silanes were initially utilized to elucidate the stereochemical course of substitution at silicon. These mechanistic investigations are to be seen alongside a handful of synthetic transformations with covalently bound silicon as the stereoinducer. While in these substrate-controlled reactions the asymmetrically substituted silicon functions as a chiral auxiliary, reagent-controlled processes have remained elusive. This account summarizes the aimed design of silicon-stereogenic silanes and their introduction to stereoselective synthesis as chiral reagents. 1 Initial Reflections 2 Design of Silicon-Stereogenic Silanes 3 Preparation of Silicon-Stereogenic Silanes 4 Enantiospecific Reductive Metalation of Chlorosilanes 5 Enantiospecific s-Bond Metathesis of Silanes with Transition-Metal Alkyls: Hydrosilylation of Prochiral Alkenes 6 Enantiospecific s-Bond Metathesis of Silanes with Transition-Metal Alkoxides: Dehydrogenative Silicon-Oxygen Coupling of Chiral Alcohols 7 Final Thoughts

show abstract

Preparation of a Privileged Silicon‐Stereogenic Silane: Classical versus Kinetic Resolution

Cited by 101 publications

References 10 publications

Conformational rigidity of silicon-stereogenic silanes in asymmetric catalysis: A comparative study

Conformational rigidity of silicon-stereogenic silanes in asymmetric catalysis: A comparative study

Chirale Erkennung mit siliciumstereogenen Silanen: außergewöhnliche Selektivitätsfaktoren bei der kinetischen Racematspaltung von donorfunktionalisierten Alkoholen

Silicon-Stereogenic Silanes in Asymmetric Catalysis

Contact Info

Product

Resources

About