The reaction of a series of 1,1-disubstituted-1-silacyclo-3-pentenes with butyllithium reagents was studied. This reaction depends critically on the substituent at silicon. 1,1-Dimethyl- or 1,1-diphenyl-1-silacyclo-3-pentene has the propensity to undergo anionic polymerization whereas 1,1-bis(4-tert-butylphenyl)-1-silacyclo-3-pentene was metalated cleanly to give the anion derived from proton abstraction on the cyclopentenyl ring. The regioselectivity of the reaction of the silacyclopentenyl anion with electrophiles was examined and found to be influenced by the steric size of the electrophile. Small electrophiles favor $ alpha$-selection while larger ones show slight $ gamma$-preference. / The regiochemistry of reactions of $ alpha$-silylallyl lithium with alkyl halides can be controlled with metal-ion complexing substituents on silicon to give selectively the $ alpha$-substituted allylsilane. The extent of $ alpha$-selection depends significantly on the nature of the ligand and solvent. Allyl (bis(2-ethoxyethyl)aminomethyl) dimethylsilane gives higher $ alpha$-selection than allylsilanes with fewer binding heteroatoms. When the ligand is chiral the alkylation reaction also proceeds stereoselectively. Changing the solvent from tetrahydrofuran to diethyl ether further increases the yield of the $ alpha$-isomer. The synthetic utility of these silyl-ligands was demonstrated by an application to the synthesis of $ alpha$-(E)-bisabolene.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.75863 |
| Date | January 1988 |
| Creators | Horvath, Raymond Frank |
| 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: 000730726, proquestno: AAINL48611, Theses scanned by UMI/ProQuest. |
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