Trimethylsilyl sodium or potassium

In an attempt to approach a measure of tt-bonding in the Al-Al bond Uhl et al. examined the alkali metal reduction of tetrakis[bis(trimethylsilyl)methyl]dialane. Sodium or potassium reduction of [(Me3Si)2HC]2Al—Al[CH(SiMe3)2]2 in di-methoxyethane (DME) produced dark blue radical monoanions of [(Me3Si)2 HC]2A1—Al[CH(SiMe3)2]2 (Eq. 2).6... 

In the case of base-induced elimination, the Peterson alkenation relies on the strong bond formed between silicon and oxygen, and the ready propensity for silicon to be attacked by alkoxide, to drive the reaction. In the original study by Peterson, the -silylcarbinols were prepared by the addition of (trimethylsilyl)methylmagnesium chloride to the carbonyl. The caibinols were subsequently eliminated by treatment with sodium or potassium hydride or with sulfuric acid to form the methylene derivatives in excellent yield. The Peterson reaction has proven to be of general utility in the synthesis of alkenes. ... 

These side reactions can be minimized by adding trimethylsilyl chloride to the reaction mixture as an alkoxide scavenger. This traps the enediolate dianion as a bis-silyl enol ether, and traps the sodium or potassium alkoxides, which are catalysts for the Dieckmann ring closure, as neutral silyl ethers." The resultant bis-siloxy cycloalkenes are either isolated or converted in situ to a-hydroxy ketones by alcoholysis or by acid hydrolysis. ... 

Most conversions of organolithium, -sodium or -potassium compounds with trimethylchlorosilane can be carried out at temperatures below 0 °C yields are often almost quantitative. The reaction is not very demanding with respect to the nature of the organic solvent. Trimethylsilylation of Grignard compounds require significantly higher temperatures [9]. 

Group. The A -[bis(trimethylsilyl)methyl] group also serves as an N-protecting group in amides and lactams. The N-[bis(trimethylsilyl)methyl] moiety is readily removed by oxidation using ceric(IV) ammonium nitrate (CAN) in aqueous acetonitrile. The initially formed A-formyl amide or lactam is readily deformylated by stirring in methanolic sodium or potassium carbonate (eqs 11, 12, and 13). ... 

Peterson went on to describe reactions of several lithiated silanes with carbonyls compounds, all giving the desired alkenes in good yields, albeit with very little stereoselectivity. In 1975 however, Peterson and Hudrlik published their studies on the stereoselective elimination of the hydroxyalkylsilyls. The reduction of 5-trimethylsilyl-4-octanone 10 was carried out with DIBAL-H to give one diastereoisomer, 11. The authors found that elimination with sodium or potassium hydride gave /ra 5-4-octene as the major isomer 12, while elimination under acidic conditions resulted in predominantly c/5-4-octene 13. Mild conditions were employed, affording stereochemical purity of up to 95% with excellent yields. 

Potassium carboxylates.1 Anhydrous potassium salts of carboxylic acids can be prepared in high yield by reaction of methyl or trimethylsilyl esters or acid chlorides or fluorides with KOSi(CH3)3 in an anhydrous solvent (equations I and II). Sodium or lithium carboxylates can be obtained from NaOSi(CH3)3 or LiOSi(CH3)3. 

A correlation between rate acceleration and the electron-donating ability of the MO group of enolates 2 shows the potassium enolatc to be superior to the lithium, sodium or trimethylsilyl derivative84. The rate enhancement, in this case, lias been attributed to a vinylogous weakening effect of the oxyanion on the 0-3 C-4, oxygen-carbon bond, similar to effects that have been encountered in anionic oxy-Cope rearrangements119. 

Chromium carbenes can also be prepared by the so-called Semmelhack-Hegedus route. Chromium hexacarbonyl is first reduced to a nucleophilic pentacarbonyl dichromate dianion 23 with sodium naphthalenide or potassium carbide. Reaction of this dianion species with an acid chloride gives a metal alkoxide that can be quenched with an electrophile to provide the desired chromate ester 24. Alternatively, the dianion can be added to an amide carbonyl to give a tetrahedral intermediated which collapses to the chromate amide 25 on treatment with trimethylsilyl chloride. 

The black binuclear complexes (jj,-ri ri -02) [Ce N(SiMe3)2 2]2-2C H2 +2 ( = 5,6), obtained in a similar manner from Ce[N(SiMe3)2]3 and dry oxygen, have either a bridging peroxide or superoxide ligand, but the 0-0 bond length data were not definitive. The preparation of related novel sodium and potassium bis(trimethylsilyl)amido (oxo)cerates(rv) is outlined in Scheme 17. Each of these... 

Addition to Ketones and Aldehydes. o -(Trimethylsilyl)-vinyUithium 1 adds to ketones and aldehydes. The adducts do not undergo the expected Peterson elimination reaction when treated with sodium hydride or potassium hydride, but the corresponding aUene can stiU he obtained if the alcohol is converted to the chloride followed by fluoride-catalyzed -elimination (eq 1). Other uses have also been made of the aUyl chlorides made in this manner they react with cuprates, or they can be oxidized to the epoxides to serve as precursors to aUene oxides. ... 

In this section primarily reductions of aldehydes, ketones, and esters with sodium, lithium, and potassium in the presence of TCS 14 are discussed closely related reductions with metals such as Zn, Mg, Mn, Sm, Ti, etc., in the presence of TCS 14 are described in Section 13.2. Treatment of ethyl isobutyrate with sodium in the presence of TCS 14 in toluene affords the O-silylated Riihlmann-acyloin-condensation product 1915, which can be readily desilylated to the free acyloin 1916 [119]. Further reactions of methyl or ethyl 1,2- or 1,4-dicarboxylates are discussed elsewhere [120-122]. The same reaction with trimethylsilyl isobutyrate affords the C,0-silylated alcohol 1917, in 72% yield, which is desilylated to 1918 [123] (Scheme 12.34). Likewise, reduction of the diesters 1919 affords the cyclized O-silylated acyloin products 1920 in high yields, which give on saponification the acyloins 1921 [119]. Whereas electroreduction on a Mg-electrode in the presence of MesSiCl 14 converts esters such as ethyl cyclohexane-carboxylate via 1922 and subsequent saponification into acyloins such as 1923 [124], electroreduction of esters such as ethyl cyclohexylcarboxylate using a Mg-electrode without Me3SiCl 14 yields 1,2-ketones such as 1924 [125] (Scheme 12.34). 

---