Synthesis and hydrolysis of phenoxy-β-chloroethylidene acetate

Conclusions We were the first to synthesize phenoxy--chloroethylidene acetate and study its acid and alkaline hydrolysis.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 937–938, May, 1966.     

Techniques for resveratrol silylation

Summary Resveratrol, a wine stilbene phytoalexin with some pharmacological properties, was extracted from red wines by MeOH elution of a Sephadex LH-20 column, used for its purification. The column extract was dried and silylated by different methods to optimize resveratrol derivatization. The resveratrol analysis was by gas chromatography and gas cromatography-mass spectrometry allowing determination of its two isomers.     

Unusual course of diazolees silylation and N-siloxycarbonylation

The N-siloxycarbonylation and transamination reactions were studied by an example of diazoles. We found that because of insufficient nucleophilicity of the nitrogen atoms in the first case only the sililylation process occurs, in the second case the low-boiling amine is replaced by the higher boiling one and the process is completed by the formation of O-silyluretans.     

Palladium-catalyzed silylation of alcohols with hexamethyldisilane

The combination of hexamethyldisilane and a catalytic amount of [PdCl(eta3-C3H5)]2-PPh3 was found to be effective for the trimethylsilylation of alcohols, where both of the two trimethylsilyl groups of hexamethyldisilane were transferred to alcohols without coproduction of any stoichiometric amount of byproduct but H2.     

Rate studies of silylation with silylamides

The rates of silylation of p-nitrophenol with N,O-bis(trialkylsilyl)acetamides in dioxane have been measured, the reaction shown to be slowed down by replacing methyl by ethyl in the trialkylsilyl group. The rates of methanolysis of some N,O-bis(aryldimethylsilyl)acetamides (I) and N-aryldimethylsilylacetamides (II) have been measured. The reactions of compounds II were found to be acid catalyzed and accelerated by electron-withdrawing substituents in the benzene ring. At 30°C the methanolysis was shown to be entropy controlled. Compounds of series I were found to be aproximately 1000 times more reactive than those of series II. Introducing a methyl at nitrogen in the monosilylamides produced a similar rate enhancing effect as introduction of a second silyl group. Promotion of (p-d)π coordination of silicon to oxygen or nitrogen in the ground state of the silylamide molecule is suggested as the factor responsible for this effect.     

Chloromethylation of polyphenylsiloxane prepolymers by silylation

Silylation of nonequilibrated phenyl-T-siloxane polycondensates by dimethylchloromethylchlorosilane involves only a small part of the silanol groups present in these prepolymers. At room temperature, silylation and condensation of the silanol groups occur at the same time. This condensation can be either intermolecular only or both intermolecular and intramolecular, depending on the initial condensation state of the prepolymer. It seems that no condensation reactions take place when the reaction is carried out with reflux. In any case, and even with strongly reactive disilazanes, no more than 35% of the silanol groups are consumed. The results give some information about a polymer, the structure of which is (after all) rather badly known.     

Borane-mediated silylation of a metal-oxo ligand

The addition of 1 equiv of HSiPh(3) to UO(2)((Ar)acnac)(2) ((Ar)acnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-(t)Bu(2)C(6)H(3)), in the presence of 1 equiv of B(C(6)F(5))(3), results in the formation of U(OSiPh(3))(OB{C(6)F(5)}(3))((Ar)acnac)(2) (1), via silylation of an oxo ligand and reduction of the uranium center. The addition of 1 equiv of Cp(2)Co to 1 results in a reduction to uranium(IV) and the formation of [Cp(2)Co][U(OSiPh(3))(OB{C(6)F(5)}(3))((Ar)acnac)(2)] (2) in 78% yield. Complexes 1 and 2 have been characterized by X-ray crystallography, while the solution-phase redox properties of 1 have been measured with cyclic voltammetry.     

Direct electrophilic silylation of terminal alkynes

[reaction: see text] A variety of alkynylsilanes were efficiently prepared via direct silylation of terminal alkynes with aminosilanes in the presence of zinc halides. Base- and nucleophile-sensitive functionalities were perfectly tolerated under the above reaction conditions. Initial mechanistic studies support the electrophilic character of this transformation.     

Zinc-catalyzed silylation of terminal alkynes.

A rapid and high-yielding silylation of terminal alkynes employing TMSOTf and catalytic quantities of Zn(OTf)2 has been developed. The reaction works well for a variety of substrates including reactive esters. Fifteen examples with yields of >90% are reported.     

Electrochemical silylation of unsaturated organofluoric compounds

Organofluoric compounds are electrolyzed in a diaphragmless cell filled with aprotic solvent containing trimethylchlorosilane. The following substances are trimethylsilylated in the electrolysis: C₆F₆, C₆F₅CI, C₆F₅H, C₆F₅CF₃, C₅F₅N, CFC1=CFC1, and CF₂=CFBr, with the introduction of one trimethylsilyl group. The silylation mechanism is established. In some case, the silylation products’ yield is increased on a copper cathode.     

Optimization of carbohydrate silylation for gas chromatography

We developed and optimized a new carbohydrate mono- and disaccharides silylation reaction, replacing pyridine and requiring lower reaction temperature and less time. Our method consists of three basic steps. The first one is oxime formation, the second one silylate derivative and the last one gas chromatography separation and quantification with an internal standard. We evaluated several solvents, including acetonitrile, hydroxylamine and aniline. We found aniline to be the best reaction media for oxime formation with hydroxylamine hydrochloride. Among silylation agents we found N,O-bis(trimethyl)trifluoroacetamide (BSTFA) was the most efficient. Together these reagents favored both a short analysis time and fewer by-products. We evaluated the method with model solutions containing: arabinose and co-eluting xylose, fructose, glucose, sucrose and salicin (internal standard) and found it suitable for processed food analysis.     

Dinitrogen silylation and cleavage with a hafnocene complex

Silylation of a hafnocene complex containing a strongly activated dinitrogen ligand, [(η(5)-C(5)H(2)-1,2,4-Me(3))(2)Hf](2)(μ(2),η(2),η(2)-N(2)), by addition of CySiH(3) resulted in N-Si and Hf-H bond formation and a compound poised for subsequent N(2) cleavage. Warming the silane addition product to 75 °C triggered N-N scission, for which the requisite electrons were provided by silyl migration. Dinitrogen cleavage coupled to N-C bond formation was also accomplished by carbonylation of the silylated product, yielding an unprecedented μ-formamidide ([NC(H)O](2-)) ligand. Subsequent treatment with HCl yielded free formamide, demonstrating that an important organic molecule can be synthesized from N(2), CO, an organosilane, and protons.     

High temperature silylation of glass capillary columns

This paper describes the results of a study on the deactivation of the surface of glass capillary columns by high temperature silylation (HTS). The different steps, leaching, washing, dehydration and HTS were optimized. A practical procedure yielding a high percentage of very good columns is given. The influence of leaching and HTS on the temperature stability and coating efficiency of capillary columns coated with OV-1 was studied. The inertness of the glass surface after HTS is demonstrated by several examples.     

Unusual transformation of nitroethyl acetate upon silylation

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, p. 2430, October, 1988.