Trimethylsilyl halide-promoted Michaelis-Arbuzov rearrangement

[reaction: see text] We describe a new, straightforward, and easy-to-handle method for achieving an unprecedented trimethylsilyl halide-catalyzed Michaelis-Arbuzov-like rearrangement. This rearrangement occurs at temperatures from room temperature to 80 degrees C and does not require addition of any alkyl halide. The scope and limitations of this new reaction are explored, as well as its mechanism.     

Ethynylisopropylgermanes and Their Trimethylsilyl Derivatives

The reaction of ethynylmagnesium bromide with chloroisopropylgermanes (i-Pr_{4 - n} GeCl_{/sub> n} , n = 1-3) was used to prepare previously unknown ethynylisopropylgermanes i-Pr_{4 - n} Ge(CCH) _n (n = 1-3). The reaction of Me₃SiCCMgBr with i-PrGeCl₃ afforded i-Pr(Me₃SiCC)_{3 - n} GeCl _n (n = 1, 2). The reaction of the monochloride with BrMdCCH gave i-Pr(HCC)₂GeCCSiMe₃, while with the dichloride, i-Pr(HCC)·Ge(CSiMe₃)₂ formed. The latter compounds were obtained by independent synthesis from i-PrGe(CCH)₃, EtMgBr, and ClSiMe₃. The reaction of (bromomagnesioethynyl)triisopropylgermane with Me₃SiCl gave i-Pr₃GeCSiMe₃.     

Trifluoromethylthiolation of Trimethylsilyl Enol Ethers

The treatment of bis-(1,2-trimethylsilyloxy)-1-cyclobutene, 1-(1-trimethylsilyloxy)cyclpentene and 1-(1-trimethylsilyloxy)cyclohexene with trifluoromethylsulfenyl chloride has been found to furnish trifluoromethylthiolated carbonyl derivatives.     

三甲硅基醚的断裂研究

Sommer等[1]首次应用（Me3SiO）2SO2向醇羟基引人三甲硅基（TMS）以保护羟基以来，已发展出很多方便有效的向醇羟基引人TMS保护基团的方法[2]．通常，立体阻碍越小的醇，其羟基越容易被硅基化，而且该TMS保护基团也就越容易在酸或碱性条件下被水解脱除[2]我们在天然产物PrehisPanolone的合成中[3]，羟基r-丁烯酸内酯2是一个关键的中间体．如何脱除前体三甲硅基醚的r-丁烯酸内酯1中的TMS保护基团是一个关键的问题．我们采用四了基氟化铵（TBAF）[4]（A）、酸性水解[5]（B）、碱性醇解[6]（C）和三氟化硼乙醚溶液（BF3-Et2O）[7]…     

Trichloromethyl Anion Chemistry from Trimethylsilyl Trichloroacetate

The reaction of trimethylsilyl trichloroacetate with aldehydes and Retones in the presence of fluoride ion gives the trichloromethyl adducts. With potassium fluoride the reaction with cyclohexenone and crotonaldehyde results in clear 1,2 addition.     

New Synthesis of Diethyl Trimethylsilyl Phosphite

Russian Journal of Organic Chemistry - Diethyl phosphonate rapidly reacted with hexamethyldisilazane at 20°C in the presence of 52 mol % of zinc(II) chloride to give 76% of diethyl...     

Pure Cellulose Nanoparticles from Trimethylsilyl Cellulose

Silyl ethers of cellulose are promising derivatives of the biopolymer because they exhibit thermoplastic behavior at higher functionalization, may be applied as intermediate in subsequent reactions and have a high tendency to form defined supramolecular structures. Trimethylsilylation can be carried out by applying ionic liquids (ILs) such as 1-ethyl-3-methylimidazolium acetate (EMIMAc) as reaction medium. Pure trimethylsilyl cellulose (TMSC) can be efficiently synthesized with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) yielding products with degrees of substitution (DS) up to 2.89. During the synthesis of highly functionalized derivatives, precipitation of the TMSC occurred, which simplifies the recycling of the IL. The tendency of TMSC toward the formation of supermolecular structures was exploited for the formation of pure cellulose nanospheres by a simple dialysis process. FTIR spectroscopy confirmed the complete removal of the TMS functions during this process. Scanning electron microscopy, dynamic light scattering, atomic force microscopy, and particle size distribution analysis showed that cellulose particles with a size of 100 to 200 nm are accessible in this simple manner.     

Trimethylsilyl and halodimethylsilylmethyl derivatives of some diamines

The reaction of chloro-and bromomethyldimethylchlorosilane with a variety of N,N,N'-trialkyldiamines resulted in solids which, on the basis of proton, ²⁹Si, and ³⁷Cl chemical shift and molecular weight data, are assumed to have a dimeric or trimeric structure (in solution) that contains a 4-coordinate silicon:

Full-size image

     

Trimethylsilyl and diethylboron derivatives of ethyl N-nitrocarbamate

Conclusions The trimethylsilyl and diethylboron derivatives of ethyl-N-nitrocarbamate were prepared.The former compound was found to exist as an equilibrium mixture of three stereoisomers, i.e., the N- and O-derivatives together with the previously unknown imide isomer. A mechanism of the tautomeric rearrangements in the system, involving both the charged ring intramolecular and the dissociative migration of the Si(CH₃)₃ group is suggested.The latter compound appears to exist in its imide form in which the boron atom is coordinated to the carbonyl group oxygen. The pyridine complex of this derivative has the N-isomer structure.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2547–2557, November, 1976.We are grateful to N. O. Cherskaya for recording the low-temperature IR spectra of (I) and to N. I. Shlykova and O. A. Luk'yanov for their help in preparing (V).     

A Simple Preparation of Trimethylsilyl Acetic Acid

A facile access to trimethylsilyl acetic acid is described. The method involves the preparation of the corresponding trimethylsilyl ester in fairly good yield (70%).     

Oxidation of bis(Trimethylsilyl)amidodifluorophosphite

Conclusions The reaction of tert-butyl hypochlorite with bis(trimethylsilyl)amidodifluorophosphite gives an intermediate quasiphosphonium salt, which decomposes losing either the trimethylsilyl group or tert-butyl group with equal probability.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1426–1428, June, 1989.     

Trimethylsilyl bis(Fluorosulfonyl)imide : An Efficient Catalyst for the Addition of Trimethylsilyl Cyanide to Carbonyl Compounds

In the presence of 1 mol% of trimethylsilyl bis(fluorosulfonyl)imide, trimethylsilyl cyanide adds efficiently to carbonyl compounds. The catalyst has been found to be more active than trimethylsilyl triflate for the above reaction.     

Oligoorganogermanes: Interplay between Aryl and Trimethylsilyl Substituents

Derivatives of main group elements containing element–element bonds are characterized by unique properties due to σ-conjugation, which is an attractive subject for investigation. A novel series of digermanes, Ar₃Ge-Ge(SiMe₃)₃, containing aryl (Ar = p-C₆H₄Me (1), p-C₆H₄F (2), C₆F₅ (3)) and trimethylsilyl substituents, was synthesized by the reaction of germyl potassium salt, [(Me₃Si)₃GeK*THF], with triarylchlorogermanes, Ar₃GeCl. The optical and electronic properties of such substituted oligoorganogermanes were investigated spectroscopically by UV/vis absorption spectroscopy and theoretically by DFT calculations. The molecular structures of compounds 1 and 2 were studied by XRD analysis. Conjugation between all structural fragments (Ge-Ge, Ge-Si, Ge-Ar, where Ar is an electron-donating or withdrawing group) was found to affect the properties.     

Homoallyl-cyclopropylcarbinyl cation manifold. Trimethylsilyl versus aryl stabilization

A series of E- and Z-1-aryl-5-trimethylsilyl-3-buten-1-yl trifluoroacetates were solvolyzed in CD3CO2D, and rates of reaction as well as products derived from these reactions were determined. Hammett plots showed a break, which was indicative of a mechanistic change from a kC process when the most electron-donating substituents were attached to the aryl group to a kDelta process involving formation of cyclized beta-silyl carbocation intermediates for electron-withdrawing groups. In the case of p-CH3O substitution (a kC extreme), the cationic intermediate captures solvent (95%) or loses a proton (5%). In the case of m-CF3 substitution (a kDelta extreme), the beta-silyl cation intermediate desilylates to give vinylcyclopropane products. Substituents with intermediate electronic properties give more complex product mixtures. Solvolysis of pure Z-trifluoroacetate (p-CH3) gives small amounts of E-trifluoroacetate (p-CH3) along with the E-substitution product. This isomerization suggests that the cyclized beta-silyl cation can isomerize and then reopen to a classical aryl-stabilized cation. By way of contrast, B3LYP/6-31G* computational studies show only cyclized beta-silyl cations as energy minima. Open kC cations are higher-energy nonminimum energy structures.     

A Convenient in Situ Preparation of Trimethylsilyl Iodide

The ability of trimethylsilyl iodide (1) to effect a variety of useful synthetic transformations has been amply demonstrated. Thus, in the presence of 1, the following conversions are reported to occur efficiently and under mild conditions: hydrolysis of ethers¹, carboxylate² and phosphonate³ esters, carbamates⁴, acetals and ketals⁵; deoxygenation of sulfoxides⁶; formation of iodomethyl methyl ether from methylal⁷; formation of iodides from alcohols⁸; decarboxylation of β-ketoesters and gem-diesters⁹ and formation and subsequent reactions of aldehyde iodohydrin trimethylsilyl ethers derived from aldehydes.¹⁰ Despite the versatility and ready availability of 1 ¹¹, routine application in organic synthesis is limited by its marked instability toward hydrolysis. This has prompted several groups to devise suitable     

A New Convenient Laboratory Synthesis of Trimethylsilyl Bromide

Trimethylsilyl bromide is prepared in a laboratory scale from trimethylsilyl 4-bromo 2-alkenoates in almost quantitative yield.     

Dialkylaminoethylation of Trimethylsilyl Esters of Trivalent Phosphorus Acids

Abstract

Dialkylaminomethylation of trimethylsilyl esters of trivalent phosphorus acids using bis(dialkylamino)methanes was carried out for the first time. This reaction is a convenient method for preparation of quaternary coordinated phosphorus compounds, including dialkylaminomethyl and functional groups. Thus trimethylsilylphosphites and -phosphonites of various structures react with bis(dialklamino)-methanes according to Arbuzov reaction in the presence of zinc chloride as a catalyst, when heated to 120°C, resulting in formation of phosphonates and phosphinates (I)