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Aspects on the Regio and Stereo Selectivity in the Hydrolsilylation of 1,3-Dienes

Gustafsson, Magnus LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

Hydrosilyleringsreaktionen är formellt en addition av en hydrosilan till ett omättat system. Reaktionen är oftast katalyserad av en övergångsmetall, och i denna process är det möjligt att påverka på vilket sätt additionen sker. Denna avhandling är en sammanfattning av fyra artiklar som behandlar regio-, stereo- och kemoselektivitet vid addition av hydrosilaner till konjugerade diener under rhodium- alternativt palladiumkatalys. En högre selektivitet innebär en mer uniform produkt. Exempelvis hade syrgas en positiv influens på regioselektiviteten i den RhCl(PPh3)3 katalyserade reaktionen mellan hydrosilaner och isopren. Som bäst uppnåddes ett 10:1 förhållande mellan reaktionens två huvudisomerer.... (More)
Popular Abstract in Swedish

Hydrosilyleringsreaktionen är formellt en addition av en hydrosilan till ett omättat system. Reaktionen är oftast katalyserad av en övergångsmetall, och i denna process är det möjligt att påverka på vilket sätt additionen sker. Denna avhandling är en sammanfattning av fyra artiklar som behandlar regio-, stereo- och kemoselektivitet vid addition av hydrosilaner till konjugerade diener under rhodium- alternativt palladiumkatalys. En högre selektivitet innebär en mer uniform produkt. Exempelvis hade syrgas en positiv influens på regioselektiviteten i den RhCl(PPh3)3 katalyserade reaktionen mellan hydrosilaner och isopren. Som bäst uppnåddes ett 10:1 förhållande mellan reaktionens två huvudisomerer. Introduktion av en kiral ligand, syntetiserad från aminosyran phenylglycin, anrikade den ena stereoisomeren i den palladiumkatalyserade reaktionen av cykliska diener med upp till 84% enantiomert överskott. (Less)
Abstract
This thesis is a summary of four papers concerning various aspects on the transition metal catalysed hydrosilylation of 1,3-dienes. The hydrosilylation reaction is formally an addition of a hydrosilane to an unsaturated system and depending on the reaction conditions, control of stereo-, regio-, and chemo-selectivity can be achieved.



Optically active heterobidentate P,N ligands were synthesised from phenylglycine and their coordination to PdCl2(CH3CN)2 was studied by 1H, 31P and 15N-1H-HMQC NMR spectroscopy. Further, the catalytic efficiency of a PdL complex was studied in the asymmetric hydrosilylation of cyclic 1,3-dienes. Enatiomeric excess up to 84% for cyclohexenol was achieved after a hydrosilylation/oxidation... (More)
This thesis is a summary of four papers concerning various aspects on the transition metal catalysed hydrosilylation of 1,3-dienes. The hydrosilylation reaction is formally an addition of a hydrosilane to an unsaturated system and depending on the reaction conditions, control of stereo-, regio-, and chemo-selectivity can be achieved.



Optically active heterobidentate P,N ligands were synthesised from phenylglycine and their coordination to PdCl2(CH3CN)2 was studied by 1H, 31P and 15N-1H-HMQC NMR spectroscopy. Further, the catalytic efficiency of a PdL complex was studied in the asymmetric hydrosilylation of cyclic 1,3-dienes. Enatiomeric excess up to 84% for cyclohexenol was achieved after a hydrosilylation/oxidation sequence of 1,3-cyclohexadiene (paper I).



The regioselectivity in the hydrosilylation of substituted 1,3-dienes catalysed by several rhodium complexes in the presence and absence of oxygen was studied. Beside the already known accelerating effect, the presence of oxygen strongly affected the product distribution in the hydrosilylation of 2-substituted 1,3-dienes. The head-product (II) was dominating under the O2-conditions, while under Ar-conditions; the tail-product (I) was produced in excess. At best, a I:II ratio of approximately 1:10 was achieved under the O2-conditions (paper II).



Other reaction parameters such as temperature, solvent, transition-metal cocatalysts and ligands also have an effect on the regioselectivity. The ligands around the catalyst-metal was found to have the largest impact on I:II ratio. A surprising catalytic difference was observed between RhCl(CS)(PPh3)2 and RhCl(CO)(PPh3)2. The former gave a I:II ratio of 70:30, while the latter gave a I:II ratio of 15:85 (paper III).



Allylsilanes can be used as effective terminator groups in electrophilic ring closure. A suitable precursor for the ring closure is an epoxy-allylsilane. The silyl unit can be introduced by a chemo-selective hydrosilylation on a functionalised diene (60%) and the following ring closure is initiated by a proper Lewis acid such as EtAlCl2 or BF3.OEt2 (50-70%) (paper IV). (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Somfai, Peter, Organisk Kemi, KTH
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Metallorganisk kemi, Organometallic chemistry, Organisk kemi, Organic chemistry, Lewis acid, electrophilic ring closure, asymmetric hydrosilylation, reaction conditions, isoprene, regioselectivity, oxygen, Wilkinsons catalyst, 15N-1H-HMQC, 31P, heterobidentate ligands, catalyst, palladium, epoxy-allylsilanes, rhodium complexes, dienes
pages
55 pages
publisher
Organic Chemistry, Lund University
defense location
Kemicentrum, Hörsal F
defense date
2005-02-11 10:30
ISBN
91-7422-070-5
language
English
LU publication?
yes
id
5b0cda31-f3c1-4c27-ba8a-a9f1abdbb253 (old id 544233)
date added to LUP
2007-10-13 12:11:25
date last changed
2016-09-19 08:45:07
@phdthesis{5b0cda31-f3c1-4c27-ba8a-a9f1abdbb253,
  abstract     = {This thesis is a summary of four papers concerning various aspects on the transition metal catalysed hydrosilylation of 1,3-dienes. The hydrosilylation reaction is formally an addition of a hydrosilane to an unsaturated system and depending on the reaction conditions, control of stereo-, regio-, and chemo-selectivity can be achieved.<br/><br>
<br/><br>
Optically active heterobidentate P,N ligands were synthesised from phenylglycine and their coordination to PdCl2(CH3CN)2 was studied by 1H, 31P and 15N-1H-HMQC NMR spectroscopy. Further, the catalytic efficiency of a PdL complex was studied in the asymmetric hydrosilylation of cyclic 1,3-dienes. Enatiomeric excess up to 84% for cyclohexenol was achieved after a hydrosilylation/oxidation sequence of 1,3-cyclohexadiene (paper I).<br/><br>
<br/><br>
The regioselectivity in the hydrosilylation of substituted 1,3-dienes catalysed by several rhodium complexes in the presence and absence of oxygen was studied. Beside the already known accelerating effect, the presence of oxygen strongly affected the product distribution in the hydrosilylation of 2-substituted 1,3-dienes. The head-product (II) was dominating under the O2-conditions, while under Ar-conditions; the tail-product (I) was produced in excess. At best, a I:II ratio of approximately 1:10 was achieved under the O2-conditions (paper II).<br/><br>
<br/><br>
Other reaction parameters such as temperature, solvent, transition-metal cocatalysts and ligands also have an effect on the regioselectivity. The ligands around the catalyst-metal was found to have the largest impact on I:II ratio. A surprising catalytic difference was observed between RhCl(CS)(PPh3)2 and RhCl(CO)(PPh3)2. The former gave a I:II ratio of 70:30, while the latter gave a I:II ratio of 15:85 (paper III).<br/><br>
<br/><br>
Allylsilanes can be used as effective terminator groups in electrophilic ring closure. A suitable precursor for the ring closure is an epoxy-allylsilane. The silyl unit can be introduced by a chemo-selective hydrosilylation on a functionalised diene (60%) and the following ring closure is initiated by a proper Lewis acid such as EtAlCl2 or BF3.OEt2 (50-70%) (paper IV).},
  author       = {Gustafsson, Magnus},
  isbn         = {91-7422-070-5},
  keyword      = {Metallorganisk kemi,Organometallic chemistry,Organisk kemi,Organic chemistry,Lewis acid,electrophilic ring closure,asymmetric hydrosilylation,reaction conditions,isoprene,regioselectivity,oxygen,Wilkinsons catalyst,15N-1H-HMQC,31P,heterobidentate ligands,catalyst,palladium,epoxy-allylsilanes,rhodium complexes,dienes},
  language     = {eng},
  pages        = {55},
  publisher    = {Organic Chemistry, Lund University},
  school       = {Lund University},
  title        = {Aspects on the Regio and Stereo Selectivity in the Hydrolsilylation of 1,3-Dienes},
  year         = {2005},
}