Liquid crystalline silicon-containing oligomers

Białecka‐Florjańczyk, Ewa; Soltysiak, Joanna

doi:10.1016/j.jorganchem.2010.04.025

Cited by 8 publications

(1 citation statement)

References 29 publications

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“…1b Liquid crystalline siloxane oligomers were investigated for their mesogenic properties. 2 Water repellent siloxanes act as antiperspirants. 3 A polyorganosiloxane 4a emulsion 4b is used for the preparation of cosmetic products.…”

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An Efficient Method for the Synthesis of Symmetrical Disiloxanes from Alkoxysilanes Using Meerwein's Reagent

Shimada

Jorapur

2012

Synlett

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We report here a new and efficient route to symmetrical disiloxanes from their corresponding alkoxysilanes using Meerwein's reagent as mediator and potassium carbonate as additive under mild reaction conditions in acetonitrile. Our methodology is very simple, economic, and high yielding. We have also proposed a reaction mechanism with the plausible silyloxonium intermediates.Siloxanes with Si-O-Si backbone are ubiquitous in nature. They have a broad range of potential applications, including health care products, dry-cleaning process, 1a and adhesives. 1b Liquid crystalline siloxane oligomers were investigated for their mesogenic properties. 2 Water repellent siloxanes act as antiperspirants. 3 A polyorganosiloxane 4a emulsion 4b is used for the preparation of cosmetic products. 4c Particularly, disiloxanes act as an important class of compounds with versatile applications. They are used in microelectronic device and sensor fabrication 5 and as liquid crystal display element. 6 Anion recognition phenomenon was observed by Kondo and Unno in the presence of disiloxane-1,3-diol. 7 Gunji and co-workers used 1,3-diphenyldisiloxane as a building block of silsesquioxanes. 8 Narumi and Miyano reported the use of disiloxane to prepare bridged calix[4]arenes. 9 Napier used disiloxanes as cross-coupling partner in Hiyama-type coupling reaction with aryl halides. 10 Marciniec efficiently used divinyl-substituted silanes and disiloxanes in cross-metathesis in the presence of Grubbs catalyst. 11 The general strategy to efficiently generate disiloxanes is via hydrosilanes. Hydrolytic oxidation of hydrosilanes in the presence of cationic oxorhenium catalyst provides disiloxanes. 12 Matsuo and Kawaguchi observed the formation of disiloxane from CO 2 and hydrosilanes using zirconium-borane complexes. 13 Chojnowski et al. used tris(pentafluorophenyl)borane as Lewis acid catalyst to produce disiloxanes via coupling reaction of hydrosilanes with alkoxysilanes. 14 Lewis acids were further utilized as catalyst in the synthesis of symmetrical disiloxanes via aerobic oxidation of hydrosilanes. 15 Schubert recently reported the use of transition-metal catalyst to generate disiloxanes from hydridosilanes. 16 In our recent report, we discovered a novel sol-gel polycondensation of tetraethoxysilane (TEOS) to silica using Meerwein's reagent (MR) 17 in acetonitrile (MeCN) solvent. 18 We extended our work on MR and successfully achieved various fluorosilanes from alkoxysilanes via nucleophilic fluorination to the silicon centre (S N 2-Si) in excellent yields (Scheme 1). 19 Here, in this work we suppressed the effect of fluoride ion by using K 2 CO 3 as an additive and demonstrated the synthesis of various symmetrical disiloxanes from their corresponding monoalkoxysilanes (Scheme 1). We further propose the possible reaction mechanism of alkoxysilanes condensation. To our knowledge this is the first report of MR-assisted alkoxysilanes condensation to corresponding symmetrical disiloxanes proceeding via silyloxonium intermediate. Scheme 1 MR-Medi...

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An Efficient Method for the Synthesis of Symmetrical Disiloxanes from Alkoxysilanes Using Meerwein's Reagent

Shimada

Jorapur

2012

Synlett

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Star‐Shaped Mesogens

Lehmann

2014

Handbook of Liquid Crystals

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Star‐shaped molecules are exciting non‐conventional mesogens in which more than two linear arms are symmertrically attached to a core building block via covalent or supramolecular bonds. The molecular structures comprise flexible, semi‐flexible and shape‐persistent scaffolds which may realize all kinds of mesophase topologies by nanosegregation. This requires different modes of self‐assembly depending on the mesogen structure, flexibility and void between the arms. Functionality can be incorporated by cores, arms and guest molecules generating multifunctional, highly organized complex materials for applications.

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Selective Hydrosilylation of Alkynes with Octaspherosilicate (HSiMe₂O)₈Si₈O₁₂

Stefanowska

Franczyk

Szyling

et al. 2018

Chemistry An Asian Journal

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Comprehensive studies on platinum-catalyzed hydrosilylation of a wide range of terminal and internal alkynes with spherosilicate (HSiMe O) Si O (1 a) were performed. The influence of the reaction parameters and the types of reagents and catalysts on the efficiency of the process, which enabled the creation of a versatile and selective method to synthesize olefin octafunctionalized octaspherosilicates, was studied in detail. Within this work, twenty novel 1,2-(E)-disubstituted and 1,1,2-(E)-trisubstituted alkenyl-octaspherosilicates (3 a-m, 6 n-t) were selectively obtained with high yields, and fully characterized ( H, C, Si NMR, FTIR, MALDI TOF or TOF MS ES analysis). Moreover, the molecular structure of the compound (Me Si(H)C=C(H)SiMe O) Si O (3 a) was determined by X-ray crystallography for the first time. The developed procedures are the first that allow selective hydrosilylation of terminal silyl, germyl, aryl, and alkyl alkynes with 1 a, as well as the direct introduction of sixteen functional groups into the 1 a structure by the hydrosilylation of internal alkynes. This method constituted a powerful tool for the synthesis of hyperbranched compounds with a Si-O based cubic core. The resulting products, owing to their unique structure and physicochemical properties, are considered novel, multifunctional, hybrid, and nanometric building blocks, intended for the synthesis of star-shaped molecules or macromolecules, as well as nanofillers and polymer modifiers. In the presented syntheses, commercially available reagents and catalysts were used, so these methods can be easily repeated, rapidly scaled up, and widely applied.

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Liquid crystalline silicon-containing oligomers

Cited by 8 publications

References 29 publications

An Efficient Method for the Synthesis of Symmetrical Disiloxanes from Alkoxysilanes Using Meerwein's Reagent

An Efficient Method for the Synthesis of Symmetrical Disiloxanes from Alkoxysilanes Using Meerwein's Reagent

Star‐Shaped Mesogens

Selective Hydrosilylation of Alkynes with Octaspherosilicate (HSiMe₂O)₈Si₈O₁₂

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Liquid crystalline silicon-containing oligomers

Cited by 8 publications

References 29 publications

An Efficient Method for the Synthesis of Symmetrical Disiloxanes from Alkoxysilanes Using Meerwein's Reagent

An Efficient Method for the Synthesis of Symmetrical Disiloxanes from Alkoxysilanes Using Meerwein's Reagent

Star‐Shaped Mesogens

Selective Hydrosilylation of Alkynes with Octaspherosilicate (HSiMe2O)8Si8O12

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Selective Hydrosilylation of Alkynes with Octaspherosilicate (HSiMe₂O)₈Si₈O₁₂