Abstract
Introducing chiral silicon centers was explored for the asymmetric Rh-catalyzed cyclization of dihydrosilanes to enantiomerically enriched spirosilanes as targets to enable access to enantiostable pentacoordinate silicates. The steric rigidity required in such systems demands the presence of two naphthyl or benzo[b]thiophene groups. The synthetic approach to the expanded spirosilanes extends Takai’s method (Kuninobu et al. in Angew Chem Int Ed 52(5):1520–1522, 2013) for the synthesis of spirosilabifluorenes in which both a Si–H and a C–H bond of a dihydrosilane are activated by a rhodium catalyst. The expanded dihydrosilanes were obtained from halogenated aromatic precursors. Their asymmetric cyclization to the spirosilanes were conducted with [Rh(cod)Cl]2 in the presence of the chiral bidentate phosphane ligands (R)-BINAP, (R)-MeO-BIPHEP, and (R)-SEGPHOS, including derivatives with P-(3,5-t-Bu-4-MeO)-phenyl (DTBM) groups. The highest enantiomeric excess of 84% was obtained for 11,11′-spirobi[benzo[b]-naphtho[2,1-d]silole] with the DTBM-SEGPHOS ligand.
Original language | English |
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Pages (from-to) | 674-684 |
Number of pages | 11 |
Journal | Topics in Catalysis |
Volume | 61 |
Issue number | 7-8 |
Early online date | 20 Apr 2018 |
DOIs | |
Publication status | Published - Jun 2018 |
Funding
Acknowledgements This work was supported by the Council for Chemical Sciences of the Netherlands Organization for Scientific Research (NWO/CW).
Funders | Funder number |
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NWO/CW | |
Nederlandse Organisatie voor Wetenschappelijk Onderzoek |
Keywords
- Asymmetric catalysis
- Silicates
- Spirosilanes