Chlorotrimethylsilane, reaction with sodium

A very short and elegant synthesis of the 16-rtiembered dilactone ( )-pyrenophorin (515) has been accomplished by the dipolar cycloaddition reaction of a trialkylsilyl nitronate (81TL735). Nitromethane was added to 3-buten-2-one and the carbonyl group of the product reduced with sodium borohydride. The nitro alcohol (511) was converted to the acrylate (512) which was then subjected to a dimerization-cyclization reaction by treatment with chlorotrimethylsilane and triethylamine in dry benzene. Hydrogenation of the mixture of isoxazoline products (513) over palladium on charcoal followed by double dehydration of the intermediate bis-/3-hydroxyketone (514) led to ( )- and meso-pyrenophorin (Scheme... 

Preparation1 This reagent can be prepared in 66% yield by reaction of triflic acid with isopropenyltrimethylsilane, CH2=C(CH3)Si(CH3)3, which is available from Petrarch or which can be prepared by a Wurtz-Fittig reaction of 2-chloro-propene with sodium and chlorotrimethylsilane in ether/HMPT. 

Synthesis and Reaction Chemistry of a,p-Unsaturated Acyl Complexes Derived from (2). Two methods for the preparation of optically active ( )- and (Z)-a,p-unsaturated iron acyls from (2) have been reported." One method involves aldol condensation of (2) with aldehydes followed by 0-methylation to produce diastereomeric acyls (18). This mixture (18) is then treated with Sodium Hydride to produce predominantly ( )-a,p-unsaturated acyl complexes (19) (eq 13). Alternatively, (2) can be depro-tonated and treated with Chlorotrimethylsilane to produce the C-silylated complex which is subsequently deprotonated and treated with an aldehyde. This Peterson alkenation produced mixtures... 

Simultaneous formation of a C-H and a C-Si bond occurred when 7-bromo-7-trimethylstan-nylbicyclo[4.1.0]heptane was thermally decomposed in chlorobenzene containing triethylsilane and gave a 1 1 stereoisomeric mixture of 7-triethylsilylbicyclo[4.1.0]heptane (1) in 49% total yield.Two similar reactions were reported to occur when a 1,1-dibromocyclopropane was treated with sodium naphthalenide in the presence of chlorotrimethylsilane. The yields were low. 

A synthetic example is taken from Sih s synthesis of castanospermine,2i2 jn which diester 272 derived from hydroxy-proline was refluxed with sodium metal and chlorotrimethylsilane in toluene. This reaction led to formation of 273, which could be isolated, and converted to the corresponding acyloin by mild acid hydrolysis. 

When the reaction was carried out on a smaller scale (e.g., 0.05-mol sulfur) the reduction of sulfur required only 4h, the reaction of sodium sulfide with chlorotrimethylsilane took 6h, and 90-95% yields of product were obtained after distillation. 

Hexamethyidisilthiane, [(CHalaSiJaS. Mol. wt, 178.44, b.p. 163°. The disilthiane is prepared by reaction of chlorotrimethylsilane with sodium sulfide (96% yield). Reduction of sulfoxides. This reagent and the related hexamethylcyclo-trisilthiane reduce sulfoxides to sulfides at 25-60° in 70-90% yield. ... 

When treated with sodium borohydride in i-PrOH, the terminal alcohol was obtained after the substrate was released from the resin via hydrolysis (eq 44). Reductive workup using triphenyl-phosphine yielded the aldehyde product after release from the resin using chlorotrimethylsilane in MeOH/i-PrOH. This removal condition proved very mild and useful as it did not interfere with the aldehyde generated in the reaction. If the ozonolysis was conducted with acetic acid in the medium and was followed by stirring in an oxygen atmosphere overnight, the carboxylic acid can be obtained after release from the resin using the aforementioned TMSCl-mediated removal condition (eq 45). 

Nitriles are, with few exceptions, not reduced by NaBHa. SulfuratedNaBHa, prepared by the reaction of sodium borohydride with sulfur in THF, is somewhat more reactive than NaBHa, and reduces aromatic nitriles (but not aliphatic ones) to amines in refluxing THF. Further activation has been realized by using the Cobalt Boride system, (NaBHa-CoCD which appears to be one of the best methods for the reduction of nitriles to primary amines. More recently it has been found that Zirconium(IV) Chloride Et2SeBr2, CuSOa, Chlorotrimethylsilane, and l2 are also efficient activators for this transformation. The NaBHa-Et2SeBr2 reagent allows the selective reduction of nitriles in the presence of esters or nitro groups, which are readily reduced by NaBHa-CoCL. 

Preparative Methods several methods for the synthesis of this azide have been reported. The procedure involving aluminum chloride is not recommended, since an explosive product is formed. Azidotrimethylsilane is now commercially available, and a representative synthetic procedure is as follows. A mixture of sodium azide and chlorotrimethylsilane is refluxed in di-n-butyl ether for 2 days and the azide is safely distilled directly from the reaction vessel. Purer compound (99% content) is obtained by redistillation of the product. Several improved conditions have been reported for the preparation of this azide. In these procedures, trimethylsUyl chloride is reacted with sodium azide either neat or in a high boiling point solvent, such as a mixture of silicone oil and polyethylene glycol. Distillation of the crude product usually provides trimethylsilyl azide (TMSA) in high purity (97.9%) and yield (97%). ... 

Preparative Methods conveniently prepared by the reduction of diphenyl diselenide with sodium in THF, followed by silyla-tion of thus formed PhSeNa with chlorotrimethylsilane. In a small scale reaction, silylation of PhSeLi, which can be prepared in situ from metallic selenium and phenyllithium in THF, is alternatively utilized. ... 

Dissolve the 3, 5 -0-(tetraisopropyldisiloxane-l,3-diyl)uridine from above in anhydrous 1,2-dichloroethane (2 L) add triethylamine (420 mL, 3 mol), and chlorotrimethylsilane (225 mL, 1.8 mol) with stirring and exclusion of moisture. After 30 min, silica gel TLC in petrol/ ethyl acetate (2 1 by vol) should show complete reaction with a new spot of RfO.39. Pour the reaction mixture into vigorously stirred IM aqueous sodium bicarbonate (5 L). Separate the organic phase, dry it (Na2S04), filter, and remove solvent in vacuo. Dry the foam by two evaporations of dry toluene (250 mL). 

Method 2. In the apparatus described above is placed 4.8-5.0g. ( 0.2 g.-atorn) of clean sodium and 8.0-8.2 g. ( 0.2 g.-atom) of clean potassium (Ilotes 3, 4). The flask is heated with a heat gun to form the low-melting alloy, and then 300-350 ml. of anhydrous ether is added from a freshly opened can. The stirrer is operated at full speed until the alloy is dispersed and then at a slower speed for the remainder of the reaction (Notes 5, 6). A mixture of 17.4 g. (0.1 mole) of diethyl succinate (Note 7), 44g. (0.4 mole) of chlorotrimethylsilane (Note 8), and 125 ml. of anhydrous ether is then added at a rate sufficient to keep the reaction under control (Note 14). The purple mixture is stirred for another 4-6 hours (Note 9) and then filtered and washed as above in a nitrogen dry-box (Note ll). The product is distilled as above forerun 0.5-2 g. to 80° (10 mm.) and then at 82-86° (10 mm.) as a colorless liquid, 13.8-16.1 g. (60-70%), 1.4323-1.4330 (Notes 15-19). 

The structurally simplest silicon reagent that has been used to reduce sulphoxides is the carbene analog, dimethylsilylene (Me2Si )29. This molecule was used as a mechanistic probe and did not appear to be useful synthetically. Other silanes that have been used to reduce sulphoxides include iodotrimethylsilane, which is selective but unstable, and chlorotrimethylsilane in the presence of sodium iodide, which is easy to use, but is unselective since it cleaves esters, lactones and ethers it also converts alcohols into iodides. To circumvent these complications, Olah30 has developed the use of methyltrichlorosilane, again in the presence of sodium iodide, in dry acetonitrile (equation 8). A standard range of sulphoxides was reduced under mild conditions, with yields between 80 and 95% and with a simple workup process. The mechanism for the reaction is probably very similar to that given in equation (6), if the tricoordinate boron atoms in this reaction scheme are replaced... 

Iodotrimethylsilane formed in situ from the reaction of chlorotrimethylsilane and sodium iodide, also effects the conversion of 2-ene-l,4-diols to 1,3-dienes (equation 16)46. Allylic thionocarbonates on heating with triphenylphosphite undergo deoxygenation (Corey-Winter reaction) to generate olefins47. This procedure has been used for making hexatrienes (equation 17)47b. 

Organosilylphosphines are conveniently prepared by cleavage of alkyldiaryl-phosphines with lithium in THF, followed by treatment with chlorotrimethyl-silane,15 and tris(trimethylsilyl)phosphine has been prepared from the reaction of chlorotrimethylsilane with a mixture of sodium and potassium phosphides.16... 

Alkyl alkanoates are reduced only at very negative potentials so that preparative scale experiments at mercury or lead cathodes are not successful. Phenyl alkanoates afford 30-36% yields of the alkan-l-ol under acid conditions [148]. Preparative scale reduction of methyl alkanoates is best achieved at a magnesium cathode in tetrahydrofuran containing tm-butanol as proton donor. The reaction is carried out in an undivided cell with a sacrificial magnesium anode and affords the alkan-l-ol in good yields [151]. In the absence of a proton donor and in the presence of chlorotrimethylsilane, acyloin derivatives 30 arc formed in a process related to the acyloin condensation of esters using sodium in xylene [152], Radical-anions formed initially can be trapped by intramolecular addition to an alkene function in substrates such as 31 to give aiicyclic products [151]. 

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