Palladium-Catalyzed Intramolecular Hydrosilylation of Alkenylsilanes:  Selective Formation of Six-Membered Silicon Heterocycles

Widenhoefer, Ross A.; Krzyzanowska, B.; Webb-Wood, Grady

doi:10.1021/om980585u

Cited by 14 publications

(2 citation statements)

References 43 publications

(60 reference statements)

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“…The concentration of the trispentafluorophenylborane catalyst also plays a key role: if the catalyst concentration is allowed to rise above 2 mol %, the formation of oligomers is observed. Interestingly, the use of other alternative catalysts, such as Speier , or Pd complexes, does not afford the target spirocycle, whereas the use of Karstedt's catalyst results in the formation of thermodynamically stable five-membered ring structures, which are inert under the conditions of photoacid catalyzed polymerization experiments.…”

Section: Resultsmentioning

confidence: 99%

Photoinduced Polysiloxane Architectures from Spirosiloxane Precursors via Intramolecular Hydrosilylation

et al. 2012

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In this letter a method is described to synthesize new polysiloxane architectures by photoacid catalysis. An oxasilaspirocycle is designed that is able to undergo a photoacid generator catalyzed ring-opening reaction leading to either a homopolymer or to copolymers with hydroxyl-terminated polydimethylsiloxane. These polymers feature a defined amount of double bonds in the backbone, which is controlled by the ratio of oxasilaspirocycle to the comonomer. The former was prepared by trispentafluorophenylborane-catalyzed intramolecular hydrosilylation of a dialkenyloxysilane with an appropriate structural motif. The UV-initiated polymerization was characterized via in situ IR spectroscopic studies to determine the rate of reaction.

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Section: Resultsmentioning

confidence: 99%

Photoinduced Polysiloxane Architectures from Spirosiloxane Precursors via Intramolecular Hydrosilylation

et al. 2012

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“…Intramolecular hydrosilylation of alkenes is an important transformation in organic synthesis . Initially investigated for unsaturated silanes, the methodology is now often applied to unsaturated alkoxy- and aminosilanes, where stereospecific oxidative cleavage of the newly formed C−Si bond enables stereodefined synthesis of diols and aminoalcohols. , The majority of examples involve metal-catalyzed 5- endo or 5- exo ring closures, although six-membered cyclizations have been reported. ,, We now report regio- and stereoselective formation of oxasilinanes and oxasilepanes via formation and cyclization of unsaturated alkoxysilanes in the presence of a nonmetal catalyst.…”

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confidence: 98%

B(C₆F₅)₃-Promoted Tandem Silylation and Intramolecular Hydrosilylation: Diastereoselective Synthesis of Oxasilinanes and Oxasilepanes

Shchepin

Dussault

2010

Org. Lett.

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B(C 6 F 5 ) 3 promotes regio-and stereoselective cyclizations of unsaturated alkoxysilanes to generate oxasilinanes and oxasilepanes. The same products are available directly from alkenols via tandem silylation and hydrosilylation.Intramolecular hydrosilylation of alkenes is an important transformation in organic synthesis.1 Initially investigated for unsaturated silanes,2 the methodology is now often applied to unsaturated alkoxy-and aminosilanes,3 where stereospecific oxidative cleavage of the newly formed C-Si bond enables stereodefined synthesis of diols and aminoalcohols. 4 , 5 The majority of examples involve metal-catalyzed 5-endo or 5-exo ring closures, although six-membered cyclizations have been reported.1 , 3 , 6 We now report regio-and stereoselective formation of oxasilinanes and oxasilepanes via formation and cyclization of unsaturated alkoxysilanes in the presence of a nonmetal catalyst.In the course of investigations into the influence of Lewis acids on the ozonolysis of unsaturated silanes, we found that addition of B(C 6 F 5 ) 3 to a solution of unsaturated alkoxysilane 1-Pr resulted in regioselective formation of oxasilinane 2-Pr with high 3,5-trans diastereoselectivity (Table 1).7 , 8 The cyclization proceeded efficiently at −78 °C or RT and in the presence of either stoichometric or catalytic B(C 6 F 5 ) 3 . Cyclization was also observed for the dimethylsilyl ether (not shown),9 but the hydrolytic instability of this class of reactants led us to abandon this thread following the discovery of the tandem cyclizations discussed later. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptThe cyclization, apparently the first intramolecular example of a known intermolecular hydrosilylation,10 was investigated further using alkoxysilanes prepared as illustrated in Scheme 1. 6-Endo cyclization onto an α-substituted styrene (3-Pr) proceeded slowly but in high yield and with high trans selectivity (Scheme 2). Cyclization onto a cyclobutene (5-Pr) proceeded much more slowly through a 6-endo pathway to furnish a modest yield of the cisfused adducts (6-Pr) as a 5:1 mixture of sidechain epimers. A bishomoallyl substrate, 7-Pr, reacted very slowly through a 6-exo pathway to furnish a trans-3,6-disubstituted-2-oxa-1-silinane (8-Pr).B(C 6 F 5 ) 3 also catalyzes the reductive silylation of alcohols,11 and we became intrigued by the possibility of tandem silylation/hydrosilylation (Table 2). B(C 6 F 5 ) 3 -promoted reaction of alkenol 1 with stoichometric Et 2 SiH 2 or Ph 2 SiH 2 generated oxasilinanes 2-Et or 2-Ph with very similar regio-and stereoselection as observed in the stepwise cyclizations. Although alcohols 3 and 5 decomposed under the tandem conditions, cyclohexenol 9 reacted to selectively furnish the 3,5-trans diastereomer of cis-fused octahydrobenzooxasilinanes 10-Et and 10-Ph; the lower yield for the Et 2 SiH 2 reaction is likely related to undesired reductive deoxygenations (vida infra). Alkenol 11, which generates an intermediate siloxane capable of undergoing cy...

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Silicon in Organic and Bioorganic Chemistry

2005

Organosilicon Chemistry VI

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Palladium-Catalyzed Intramolecular Hydrosilylation of Alkenylsilanes: Selective Formation of Six-Membered Silicon Heterocycles

Cited by 14 publications

References 43 publications

Photoinduced Polysiloxane Architectures from Spirosiloxane Precursors via Intramolecular Hydrosilylation

Photoinduced Polysiloxane Architectures from Spirosiloxane Precursors via Intramolecular Hydrosilylation

B(C₆F₅)₃-Promoted Tandem Silylation and Intramolecular Hydrosilylation: Diastereoselective Synthesis of Oxasilinanes and Oxasilepanes

Silicon in Organic and Bioorganic Chemistry

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Palladium-Catalyzed Intramolecular Hydrosilylation of Alkenylsilanes: Selective Formation of Six-Membered Silicon Heterocycles

Cited by 14 publications

References 43 publications

Photoinduced Polysiloxane Architectures from Spirosiloxane Precursors via Intramolecular Hydrosilylation

Photoinduced Polysiloxane Architectures from Spirosiloxane Precursors via Intramolecular Hydrosilylation

B(C6F5)3-Promoted Tandem Silylation and Intramolecular Hydrosilylation: Diastereoselective Synthesis of Oxasilinanes and Oxasilepanes

Silicon in Organic and Bioorganic Chemistry

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B(C₆F₅)₃-Promoted Tandem Silylation and Intramolecular Hydrosilylation: Diastereoselective Synthesis of Oxasilinanes and Oxasilepanes