Heterophase polymerization of styrene in the presence of organosilicon compounds of various natures

The heterophase polymerization of styrene has been carried out in the presence of surfactants—organosilicon compounds with different solubilities in aqueous and styrene phases and surface activities at the interface. It has been demonstrated that the stability of polymer suspensions prepared with water-insoluble organosilicon compounds is much higher than that in the presence of organosilicon surfactants soluble in organic and aqueous phases. In the former case, suspensions with narrower particle-size distributions are produced. The stability of polymer microspheres prepared at various monomer-to-water volume ratios has been tested. An increase in the monomer concentration above 25 vol % leads to the loss of system stability.     

具有生物活性的有机硅化合物研究近况

生物有机硅化合物的研究进展迅速,而且越来越受到人们的重视。实际上,它是有机硅化学的一个新的分支。本文对有机硅化合物的毒理学、有机硅药物化学以及有机硅农药作了简要的论述。     

氟代有机硅化合物的合成新方法

本工作利用CuCl/HOC₂H₄NH₂催化剂,将1,2-二溴四氟乙烷与烯基有机硅化合物进行加威反应,制备了一系列新的含氟有机硅化合物,并进行了分析鉴定。对影响反应的诸因素做了初步探讨。     

Comparative study of the biological activity of organosilicon and organogermanium compounds

The literature data and the results of our own investigations on the comparative study of the biological activity of isostructural organogermanium and organosilicon compounds have been summarized. It has been shown that the series of organogermanium and organosilicon compounds is more active than the carbon analogues, the majority of organogermanium compounds are less toxic than the sila analogues, the biological activity of the compounds under study appears to be similar but can dramatically differ in the degree of activity, and, moreover, in some particular cases sila and germa analogues exhibit the opposite biological effects.     

Nickel-catalyzed cross-couplings of organosilicon reagents with unactivated secondary alkyl bromides

A metal-catalyzed cross-coupling of organosilicon compounds with alkyl halides has been developed. Noteworthy attributes of the method are its scope (secondary electrophiles), its high functional-group compatibility, and the air stability of the catalyst components.     

Pyridylsilanes in the synthesis of heterocycles (review)

The desilylation of pyridylsilanes and pyridylmethylsilanes is one of the most characteristic reactions of organosilicon derivatives of pyridine, and it has been shown to be possible to utilize this reaction in organic synthesis. In many instances, desilylation affords difficultly-accessible pyridine derivatives, which have also been synthesized by insertion of aldehydes into the Si-C bond in pyridylsilanes and reactions of organosilicon pyridinium compounds. 2-Trimethylsilylmethylpyridine has been found to undergo the largest number of reactions leading to the formation of a variety of compounds containing the pyridine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 5–13, January, 1987.     

Insecticidal potency of certain organosilicon compounds

A small series of organosilicon compounds were screened for efficacy against the housefly Musca domestica. The activity of organosilicon compounds is attributed to the silicon atom, the presence of halogens and the alkyl groups.     

Carbon-carbon bond-forming enantioselective synthesis of chiral organosilicon compounds by rhodium/chiral diene-catalyzed asymmetric 1,4-addition reaction

[reaction: see text] A new synthetic method for chiral organosilicon compounds through a rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to beta-silyl alpha,beta-unsaturated carbonyl compounds has been developed. By employing (R,R)-Bn-bod* as a ligand, a range of arylboronic acids can be coupled with these substrates in very high enantiomeric excess. The resulting beta-silyl 1,4-adducts can be converted to beta-hydroxy carbonyl compounds or allylsilanes while retaining their stereochemical information.     

Analyse von organosiliciumverbindungen

Zusammenfassung Bei der Analyse von technischem Hexamethyldisiloxan wurden in den höhersiedenden Destillationsanteilen eine Reihe von bisher wenig bekannten niedermolekularen Organosiliciumverbindungen mit siloxanartiger Struktur gefunden. Die Trennung und Identifizierung der Komponenten der Gemische von verzweigten Methyl- und Methylhydroxiloxanen erfolgte durch gas-chromatographische Methoden in Verbindung mit der Massenspektrometrie.

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Analysis of organosilicon compounds VII separation and identification of branched low molecular weight methyl-and methylhydrosiloxanes by GC/MS

Summary A series of unusual, low molecular weight organosilicon compounds with the siloxane structure has been found as a result of the analysis of hexamethyldisiloxane by gas chromatography. The components of the mixture of branched, low molecular weight methyl- and methylhydrosiloxanes have been identified by gas chromatography and mass spectrometry.

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VI. Mitteilung: Coll. Czech. Chem. Comm.36, 3497 (1971).     

Silicon-based cross-coupling reaction: an environmentally benign version

Much attention has been paid to the cross-coupling reaction of organosilicon compounds due to their stability, non-toxicity, and natural abundance of silicon. In addition, the silicon-based cross-coupling has many advantages over other cross-coupling protocols. Successful examples of the silicon-based cross-coupling reaction are reviewed, focusing especially on the advances made in the last decade. Having had a number of highly effective palladium catalysts developed mainly for other cross-coupling reactions, the development of the silicon-based protocol owes heavily to the design of organosilicon reagents which effectively undergo transmetalation, a key elemental step of the silicon-based cross-coupling reaction. This tutorial review thus classifies various organosilicon reagents depending on substituents on silicon and surveys their cross-coupling reactions with various electrophiles.     

Chromatographic separation of asymmetric organosilicon compounds on cellulose and amylose stationary phases. The stereochemistry of functional transformation reactions

Summary Silicon compounds, especially silanes, have been separated on cellulose carbamate and amylose carbamate stationary phases. Reasonable recognition is achieved in the separation of organosilicon compounds on cellulose carbamate. Stereoselectivity at the asymmetric silicon center in functional transformation reactions is discussed.     

4-Silalactones and 4-silalactams

A general method for the preparation of organosilicon lactones and lactams in which a silicon atom attached to two carbon atoms is present in the -position to the heteroatom O or N has been developed. A new reaction with acyloxysilanes has been observed for a number of silicon compounds containing a chloromethyl radical, which consists in the replacement of the chlorine by the acyl radical.     

Structure-reactivity relationships in organosilicon chemistry revisited

Available quantitative data of the reactivity of organosilicon compounds were subjected to correlation analysis. As an alternative to the carbon chemistry values, the scale of steric constants E _S (Si) can be used for organosilicon compounds and the inductive effect is best expressed by two terms, involving the parameter of electronegativity of substituents. Alkyl substituents contribute to the reactivity exclusively through their steric effects, steric and polar effects in silicon compounds are additive and the resonance effect is insignificant. The correlation analysis can be employed in investigations of organosilicon reactions along with other methods.      

The synthesis of alkenylsilanes by the high-temperature condensation of unsaturated compounds with silicon hydrides

Summary The general character of the new high-temperature reaction of unsaturated hydrocarbons with silicon hydrides, leading to the formation of unsaturated organosilicon compounds, has been shown on the basis of new examples.     

Reactions of trichloromethyl radicals with organosilicon compounds

The photolysis of carbon tetrachloride in the presence of a number of organosilicon compounds has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the organosilane. Arrhenius parameters for hydrogen atom transfer were determined relative to those for trichloromethyl radical combination. The activation energies for the reaction of methyl, trifluoromethyl, and trichloromethyl radicals with organosilicon compounds are compared and the results rationalized in terms of polar effects.     

Determination of alkali metals by laser-induced atomic-ionization in flames

The technique of laser-induced atomic-ionization (AI) in flames has been used for direct determination of Na, K, Rb, and Cs in samples such as water, high-purity alkali metals and their salts and polymeric organosilicon compounds. Different procedures for sample introduction into the flame were studied: (a) the sample was placed onto the cathode of the detector (this gave limits of detection for Na and Cs of 4 x 10(-16) and 2 x 10(-15) g, respectively), (b) electrothermal vaporization and (c) aspiration of the sample into the flame. To reduce the interference of SiO(2) in the AI determination of K in polymeric organosilicon compounds (at the level of 10(-3)-10(-5)%), a procedure involved additional electrical heating of the FID cathode was developed. The efficiency of certain schemes for the laser stepwise and two-photon excitation of atoms was compared for determination of Na.     

生物有机硅化合物研究新进展

本文概述了近十几年生物有机硅化学的新进展。全文分三部分:1)利用有机硅基取代有机药物中的活性官能团的硅基化反应;2)有机药物中的某一碳原子被硅原子取代的硅药(sila-drugs)研究;3)在有机药物中没有类似结构的具有生物活性的新型有机硅化合物研究。     

某些新的氟代有机硅化合物的合成

本文用含硅氢键化合物与含双键的氟化合物的加成反应,制备了一系列未见报导的含氟有机硅化合物。在用氯丙烯与2,2,3,3-四氟丙醇制2,2,3,3-四氟丙基烯丙醚时,对方法进行了改进,提高了产率。本文还报道了含氟有机硅聚合物方面的工作。     

3-dinitrobenzoylhydrazones of organosilicon carbonyl compounds

Conclusions The reaction of 3,5-dinitrobenzoylhydrazide with organosilicon aldehydes and ketones was investigated. It was shown that this reagent forms readily crystallizing 3,5-dinitrobenzoylhydrazones and is suitable for the identification of organosilicon carbonyl compounds.