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Synthesis and Reactivity Studies of Zwitterionic Silenes and 2-Silenolates
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen, Avdelningen för organisk kemi.
2004 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This thesis describes synthesis and reactivity studies of 2-amino-2-siloxysilenes and 2-silenolates, species that are strongly influenced by reversed Si=C bond polarization, i.e. an Siδ-=Cδ+ polarization as compared to the natural Siδ+=Cδ- polarization. Because of the reversed polarization, the 2-amino-2-siloxysilenes are zwitterions and the 2-silenolates are predominantly described by the resonance structure with the negative charge at Si.

Transient zwitterionic 2-amino-2-siloxysilenes are formed thermolytically from carbamylpolysilanes (tris(trimethylsilyl)silylamides) and trapped with 1,3-dienes in nearly quantitative yields. These silenes have structure and reactivity characteristics that differ from earlier studied Si=C bonded compounds. They are thermodynamically stable toward dimerization and react with 1,3-dienes to give exclusively [4+2] cycloadducts. Their reactions with 1,3-dienes proceed in accordance with inverse electron demand (IED) Diels-Alder reactions which is explained by the electron-rich nature of these silenes. The 2-amino-2-siloxysilenes are also less reactive toward alcohols than earlier silenes. Hence, alcohols do not react with 2-amino-2-siloxysilenes but with the silene precursor, the carbamylpolysilanes, leading to alkoxysilanes in high yields. The latter reaction represents a novel base-free synthetic protocol for protection of primary and secondary alcohols with the fluoride resistant but photolabile tris(trimethylsilyl)silyl group.

Another class of formally Si=C bonded compounds, metal 2-silenolates, has been formed in high yields using a novel facile method. Reaction of acyl- and carbamylpolysilanes with potassium tert-butoxide in tetrahydrofurane gives potassium 2-silenolates. The potassium 2-silenolates are stable at room temperature, in contrast to earlier lithium 2-silenolates that degrade rapidly at ambient temperature. The first crystallisable complex of a 2-silenolate was formed and characterized by X-ray crystallography. This 2-silenolate has a pyramidal central Si (ΣSi = 317.8°), and an Si-C single rather than Si=C double bond (r(SiC) = 1.926 Å). The potassium 2-silenolates give exclusively Si alkylated products with alkyl halides and only [4+2] cycloadducts with 1,3-dienes.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis , 2004. , s. 60
Serie
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1034
Emneord [en]
Organic chemistry, Silicon, Zwitterionic Silene, 2-Silenolate, Diels-Alder Reaction, Silacyclohexene, X-ray Crystallography
Emneord [sv]
Organisk kemi
HSV kategori
Identifikatorer
URN: urn:nbn:se:uu:diva-4650ISBN: 91-554-6080-1 (tryckt)OAI: oai:DiVA.org:uu-4650DiVA, id: diva2:165374
Disputas
2004-11-26, B41, BMC, Husargatan 3, Uppsala, 13:15
Opponent
Veileder
Tilgjengelig fra: 2004-11-03 Laget: 2004-11-03bibliografisk kontrollert
Delarbeid
1. Evidence for Formation of Silenes Strongly Influenced by Reversed Si=C Bond Polarity
Åpne denne publikasjonen i ny fane eller vindu >>Evidence for Formation of Silenes Strongly Influenced by Reversed Si=C Bond Polarity
Vise andre…
2002 Inngår i: Organic Letters, ISSN 1523-7060, Vol. 4, nr 11, s. 1915-1918Artikkel i tidsskrift (Fagfellevurdert) Published
Identifikatorer
urn:nbn:se:uu:diva-92331 (URN)
Tilgjengelig fra: 2004-11-03 Laget: 2004-11-03bibliografisk kontrollert
2. Formation of Transient Zwitterionic Silenes and Their Diels-Alder Reactions with 1,3-Dienes: Mechanism and Stereoselectivity
Åpne denne publikasjonen i ny fane eller vindu >>Formation of Transient Zwitterionic Silenes and Their Diels-Alder Reactions with 1,3-Dienes: Mechanism and Stereoselectivity
Vise andre…
Inngår i: Journal of Americal Chemical Society, ISSN 0002-7863Artikkel i tidsskrift (Fagfellevurdert) Submitted
Identifikatorer
urn:nbn:se:uu:diva-92332 (URN)
Tilgjengelig fra: 2004-11-03 Laget: 2004-11-03bibliografisk kontrollert
3. The First Unsuccesful attempt to Add Alcohols to a Silene
Åpne denne publikasjonen i ny fane eller vindu >>The First Unsuccesful attempt to Add Alcohols to a Silene
Inngår i: Organometallics, ISSN 0276-7333Artikkel i tidsskrift (Fagfellevurdert) Submitted
Identifikatorer
urn:nbn:se:uu:diva-92333 (URN)
Tilgjengelig fra: 2004-11-03 Laget: 2004-11-03bibliografisk kontrollert
4. The First Isolable 2-Silenolate
Åpne denne publikasjonen i ny fane eller vindu >>The First Isolable 2-Silenolate
2003 Inngår i: Angewandte Chemie International Eddition, ISSN 1433-7851, Vol. 42, nr 14, s. 1640-1642Artikkel i tidsskrift (Fagfellevurdert) Published
Identifikatorer
urn:nbn:se:uu:diva-92334 (URN)
Tilgjengelig fra: 2004-11-03 Laget: 2004-11-03bibliografisk kontrollert
5. Potassium 1-N,N-Dialkylamino-2,2-bis(trimethylsilyl)-2-Silenolates: Heavy Enolates with Remarkable Stability
Åpne denne publikasjonen i ny fane eller vindu >>Potassium 1-N,N-Dialkylamino-2,2-bis(trimethylsilyl)-2-Silenolates: Heavy Enolates with Remarkable Stability
Vise andre…
Manuskript (Annet vitenskapelig)
Identifikatorer
urn:nbn:se:uu:diva-92335 (URN)
Tilgjengelig fra: 2004-11-03 Laget: 2004-11-03 Sist oppdatert: 2010-01-13bibliografisk kontrollert

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