Stereochemical study on polymers with stereogenic silicon atoms

Kawakami, Yusuke; Yuning, LI

doi:10.1007/s10965-006-0105-0

Cited by 7 publications

(2 citation statements)

References 47 publications

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“…Oishi, Moon, Janvikul and Kawakami have reported the preparation of syndiotactic PMPS by a Rhcatalyzed stereoselective cross-dehydrocoupling polymerization of optically active 1,3-dimethyl-1,3-diphenyldisiloxane derivatives [11], however, the resulting polymers were somewhat low in number-average molar mass (3,100≤M n ≤ 7100 gmol −1 ). Kawakami has also written a helpful review of this work and of related polymer systems [12].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Isotactic Rich Poly(methylphenylsiloxane) by Living Anionic Ring-Opening Polymerization

Ahn

Clarson

2011

Silicon

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Linear poly(methylphenylsiloxane) (PMPS) was prepared by the living anionic ring-opening polymerization of cis-2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane (cis-P 3 ). The resulting linear PMPS was shown by NMR to be highly stereoregular and remarkably high in meso-meso fraction and proposed isotactic content (~80%). Tetrahydrofuran (THF) was used as the solvent and it is noted that THF also acts as a promoter for the system by increasing the reactivity of the silanolate nucleophile at the end of the propagating chain. It is proposed that this increase in the reactivity occurs preferentially in the intermolecular (propagating) reaction. The evidence for this proposed hypothesis is the exclusive production of meso-meso and meso-racemic triads in the linear PMPS as evidenced by NMR. As the reaction temperature was increased, the rate of polymerization increased and yet the tacticity of the polymer was not affected. It is therefore clear that there was no significant amount of back-biting (intramolecular) reaction for the temperatures and time intervals studied here, despite the fact that ring-chain equilibration is commonly observed in ring-opening siloxane polymerizations. Had the reversion reaction been present, then scrambling of the chain stereoregular sequences would have been observed by an equilibration mechanism. It is well established that phenyl-phenyl interactions (π-π stacking)can stabilize certain local conformations in PMPS chains and hence we propose that these phenyl-phenyl interactions may prevent back-biting reactions for PMPS under the kinetic conditions employed here.

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Section: Introductionmentioning

confidence: 99%

Synthesis of Isotactic Rich Poly(methylphenylsiloxane) by Living Anionic Ring-Opening Polymerization

Ahn

Clarson

2011

Silicon

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“…Compared to the synthesis of chiral carbon compounds, synthetic routes to chiral compounds with a stereogenic silicon center, which is a higher homologue of carbon, remain less explored 3 – 67 . After many pioneering studies, chiral organosilicon compounds that bear silicon stereocenters have recently shown attractive and widespread application prospects in organic synthesis 5 – 13 , materials science 14 – 19 , medicinal chemistry 20 – 24 , and polymer chemistry 25 , 26 due to their unique electronic and physical properties. The development of synthetic methods for such silicon-stereogenic optically active compounds has also become an important research subject 27 – 32 .…”

Section: Introductionmentioning

confidence: 99%

Stereospecific synthesis of silicon-stereogenic optically active silylboranes and general synthesis of chiral silyl Anions

Wang,

Feng,

Jiang

et al. 2023

Nat Commun

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Silicon-stereogenic optically active silylboranes could potentially allow the formation of chiral silyl nucleophiles as well as the synthesis of various chiral silicon compounds. However, the synthesis of such silicon-stereogenic silylboranes has not been achieved so far. Here, we report the synthesis of silicon-stereogenic optically active silylboranes via a stereospecific Pt(PPh3)4-catalyzed Si–H borylation of chiral hydrosilanes, which are synthesized by stoichiometric and catalytic asymmetric synthesis, in high yield and very high or perfect enantiospecificity (99% es in one case, and >99% es in the others) with retention of the configuration. Furthermore, we report a practical approach to generate silicon-stereogenic silyl nucleophiles with high enantiopurity and configurational stability using MeLi activation. This protocol is suitable for the stereospecific and general synthesis of silicon-stereogenic trialkyl-, dialkylbenzyl-, dialkylaryl-, diarylalkyl-, and alkylary benzyloxy-substituted silylboranes and their corresponding silyl nucleophiles with excellent enantiospecificity (>99% es except one case of 99% es). Transition-metal-catalyzed C–Si bond-forming cross-coupling reactions and conjugate-addition reactions are also demonstrated. The mechanisms underlying the stability and reactivity of such chiral silyl anion were investigated by combining NMR spectroscopy and DFT calculations.

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Chiral Silicon Molecules

Igawa

Tomooka

2019

Organosilicon Chemistry

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Stereochemical study on polymers with stereogenic silicon atoms

Cited by 7 publications

References 47 publications

Synthesis of Isotactic Rich Poly(methylphenylsiloxane) by Living Anionic Ring-Opening Polymerization

Synthesis of Isotactic Rich Poly(methylphenylsiloxane) by Living Anionic Ring-Opening Polymerization

Stereospecific synthesis of silicon-stereogenic optically active silylboranes and general synthesis of chiral silyl Anions

Chiral Silicon Molecules

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