Silicon methylene

Many investigations of alkyl and aryl chlorosilanes have been reported (125, 220, 225, 254). The probability of cleavage of the R—Si bond is found to decrease with increase in the size of R (220). Methylsilanes (143) and hydrocarbons with trialkylsilyl groups (145) are discussed and extensive studies of linear and cyclic silicon-methylene compounds are also available (22-24, 105-107, 225). Russian workers have looked at alkylsilanes (68), silacycloalkanes (69), and silylvinylacetylenes (144, 195). Silicon-carbon... 

The Peterson reaction has two more advantages over the Wittig reaction 1. it is sometimes less vulnerable to sterical hindrance, and 2. groups, which are susceptible to nucleophilic substitution, are not attacked by silylated carbanions. The introduction of a methylene group into a sterically hindered ketone (R.K. Boeckman, Jr., 1973) and the syntheses of olefins with sulfur, selenium, silicon, or tin substituents (D. Seebach, 1973 B.T. Grdbel, 1974, 1977) illustrate useful applications. The reaction is, however, more limited and time consuming than the Wittig reaction, since metallated silicon derivatives are difficult to synthesize and their reactions are rarely stereoselective (T.H. Chan, 1974 ... 

Other, removable cation-stabilizing auxiliaries have been investigated for polyene cyclizations. For example, a sdyl-assisted carbocation cyclization has been used in an efficient total synthesis of lanosterol. The key step, treatment of (257) with methyl aluminum chloride in methylene chloride at —78° C, followed by acylation and chromatographic separation, affords (258) in 55% yield (two steps). When this cyclization was attempted on similar compounds that did not contain the C7P-silicon substituent, no tetracycHc products were observed. Steroid (258) is converted to lanosterol (77) in three additional chemical steps (225). 

The most widely used method of analysis for methylene chloride is gas chromatography. A capillary column medium that does a very good job in separating most chlorinated hydrocarbons is methyl silicone or methyl (5% phenyl) silicone. The detector of choice is a flame ionization detector. Typical molar response factors for the chlorinated methanes ate methyl chloride, 2.05 methylene chloride, 2.2 chloroform, 2.8 and carbon tetrachloride, 3.1, where methane is defined as having a molar response factor of 2.00. Most two-carbon chlorinated hydrocarbons have a molar response factor of about 1.0 on the same basis. 

Monomers 24 and 25 behave differently when exposed to catalyst 14, shown in Fig. 8.15. Divinyltetramethyldisiloxane 24 is found to be metathesis inactive due to similar steric inhibitions experienced with divinyldimethylsilane. Monomer 25 is synthesized with one additional methylene spacer unit between the silicon atom and the olefin moiety, which then is reacted with Schrock s [Mo] catalyst. Here, metathesis occurs quite readily, exclusively forming a seven-membered cychc molecule (26) instead of polymer. The formation of the cyclic product can be explained by tire Tliorpe-Ingold effect.15... 

Several variations of the solvent removal technique were developed (6,7). For the PCPP-SA, 20 80, M = 16,000, microspheres were prepared as follows 1 g polymer was dissolved in 1 ml methylene chloride, drug or dye was suspended in the solution, mixed, dropped into silicon oil containing 1-5% of Span 85, and stirred at a known stirring rate. Stirring was done using an overhead stirrer and a three-blade impeller. After 1 hr, petroleum ether was introduced and stirring was continued for another hour. The microspheres were isolated by filtration, washed with petroleum ether, dried overnight in a lyophilizer, sieved, and stored in a freezer. 

In this case a different method was used 2 g polymer was dissolved in 10 ml of methylene chloride, drug was added, and the mixture was suspended in silicon oil containing Span 85 and a known amount of methylene chloride. The amount of methylene chloride depended on the type and molecular weight of the polymer used. For example. 

DMSO or other sulfoxides react with trimethylchlorosilanes (TCS) 14 or trimefhylsilyl bromide 16, via 789, to give the Sila-Pummerer product 1275. Rearrangement of 789 and further reaction with TCS 14 affords, with elimination of HMDSO 7 and via 1276 and 1277, methanesulfenyl chloride 1278, which is also accessible by chlorination of dimethyldisulfide, by treatment of DMSO with Me2SiCl2 48, with formation of silicon oil 56, or by reaction of DMSO with oxalyl chloride, whereupon CO and CO2 is evolved (cf also Section 8.2.2). On heating equimolar amounts of primary or secondary alcohols with DMSO and TCS 14 in benzene, formaldehyde acetals are formed in 76-96% yield [67]. Thus reaction of -butanol with DMSO and TCS 14 gives, via intermediate 1275 and the mixed acetal 1279, formaldehyde di-n-butyl acetal 1280 in 81% yield and methyl mercaptan (Scheme 8.26). Most importantly, use of DMSO-Dg furnishes acetals in which the 0,0 -methylene group is deuter-ated. Benzyl alcohol, however, affords, under these reaction conditions, 93% diben-zyl ether 1817 and no acetal [67]. 

In the molecule of 4-methylene-3-borahomoadamantane derivative 79, the structure of which was determined by X-ray analysis, the six carbon atoms of the triene system, the two boron and two silicon atoms all lie in one plane within experimental error (mean deviation 1.4 pm). The boron atoms deviate from the trigonal-planar geometry, since the sum of bond angles around the atoms is only 355.8° instead of 360°, as usually encountered in triorganoboranes. Considerable distortions of the bond angles at the terminal C-C double bond occurs in the vicinity of the boron atoms B-C(4)-C(ll) 130.60(19)° and B-C(4)-C(5) 107.38(17)° <2002CEJ1537>. 

Germanium analogs, silicon hydrides, 6 Germicidin, ketone carbonyl to methylene... 

Nonvolatile memory (NVM), silicon-based semiconductors in, 22 257-258 Nonvolatile methylene chloride extract (NVMCE), 23 158... 

FIGURE 3 2 Solvent extraction efficiencies (EF) as functions of dielectric constants (D), solubility parameters (6), and polarity parameters (P and E -). Solvents studied silicon tetrachloride, carbon disulfide, n pentane. Freon 113, cyclopentane, n-hexane, carbon tetradiloride, diethylether, cyclohexane, isooctane, benzene (reference, EF 100), toluene, trichloroethylene, diethylamine, chloroform, triethylamine, methylene, chloride, tetra-hydrofuran, l,4 dioxane, pyridine, 2 propanol, acetone, ethanol, methanol, dimethyl sulfoxide, and water. Reprinted with permission from Grosjean. ... 

Uses Coolant and refrigerant herbicide and fumigant organic synthesis-methylating agent manufacturing of silicone polymers, pharmaceuticals, tetramethyl lead, synthetic rubber, methyl cellulose, agricultural chemicals and nonflammable films preparation of methylene chloride, carbon tetrachloride, chloroform low temperature solvent and extractant catalytic carrier for butyl rubber polymerization topical anesthetic fluid for thermometric and thermostatic equipment. 

In the reaction with ferrocene, allyldimethylchlorosilane reacts at 0 °C, allyl-(methyl)dichlorosilane reacts at the reflux temperature of methylene chloride, but allylsilanes containing two or more chlorine substituents at the silicon do not give alkylation products. In alkylations of ferrocene, allyldimethylchlorosilane shows the highest activity, allyl(methyl)dichlorosilane is less reactive, and allylsilanes containing two or more chlorine-substituents at the silicon have no activity. Allyl-trimethylsilane reacts with both benzene and ferrocene to give allylsilylation products but no alkylation product. 

Samples of both fulvic and humic acids were suspended in methanol and methylated with diazomethane. Both H and spectra of the free acids were obtained, at 299.94 MHz and 75.42 MHz respectively, on a Varian XL-300 spectrometer having a Nicolet TT-100 PET accessory. Spectra were obtained in D2O, in a 12-mm tube, with deuterated TSP (sodium 3-(trimethylsilyl)propionate-, , 3,3- 4) added as internal reference. GC/MS of methylated acids was conducted on a Hewlett-Packard Model No 5995 GC/MS/DA system equipped with a fused silica capillary column (12 m x. 020 mm ID, Hewlett Packard) internally coated with crosslinked methylene silicone. Infrared spectra were obtained with solid samples dispersed in KBr pellets, by using a Beckman IR-33 spectrophotometer. The various absorption peaks in IR and NMR were interpreted conventionally (9-10). 

The first ring expansion of a 1,2,4-trioxolane to a 1,2,4-trioxane was observed with (47) where the orientation of the peroxide group was crucial in assisting the triflate to leave (Equation (2)). A 1,2-peroxide shift then follows with loss of silicon giving the methylene substituted 1,2,4-trioxane (48) as the product <91JA8168>. The equatorial triflate does not undergo rearrangement. 

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