Hydrosilation of $ alpha, beta$-unsaturated carbonyl compounds catalyzed by hydridotetrakis(triphenylphosphine)rhodium(I) (2.20) was found to be highly regioselective, depending on the type of silicon hydrides used. Diphenylsilane was found to give 1,2-hydrosilation (100%), whereas dimethylphenylsilane and other monohydrosilanes gave 1,4-addition (100%). / The kinetic isotope effect of the hydrosilation reaction was examined. A kinetic isotope effect of $k sb{H}/k sb{D}=2$ was observed in the hydrosilation of acetophenone (2.78) by dihydrosilane, $ rm H sb2SiPh sb2$ (2.21) and $ rm D sb2SiPh sb2$ (2.83), catalyzed by the complex 2.20. While a mixture of 1:1 labeled and unlabeled sec-phenethyl alcohols was obtained for the same reaction with monohydrosilane, $ rm HSiMe sb2Ph$ (2.14) and DSiMe$ sb2$Ph (2.86). / A mechanism was proposed to account for the regioselection and the kinetic isotope effect. With the proposed intermediate O in Chart 2.5,$ sp*$ when R $ ne$ H, the hydrosilation proceeds at the rhodium center to give the 1,4-selection product; when R = H, the reaction occurs at the silicon center to generate the 1,2-reduction product. / The reaction catalyzed by 2.20 was also diastereoselective, in both 1,2-hydrosilation (up to 100% de) and 1,4-hydrosilation (84% de) of $ alpha, beta$-unsaturated ketones. / A moderate enantiomeric excess was achieved in the asymmetric hydrosilation of prochiral ketones with chiral complexes derived from complex 2.20 with chiral phosphine ligands (up to 78% ee), and with chiral oxazolinyl compound 2.139 (up to 46% ee). Two C$ sb3$ symmetric ligands have been designed and synthesized, which were found to be too unstable to form C$ sb3$-metal complexes. ftn$ sp*$Please refer to the dissertation for diagram.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.40303 |
| Date | January 1995 |
| Creators | Zheng, Guo Zhu. |
| Contributors | Chan, T. H. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001537871, proquestno: NN12522, Theses scanned by UMI/ProQuest. |
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