5- Silyl compounds

The silylated compound can be reacted further with other organohthium compounds to give substituted silylated difluorovinyl compounds (equation 34)... 

Reaction of 40% glioxal with silylated compounds 308 (97SL799, 99SL1094, OOJOC4435) and 310 (97SL799) gave a diastereomeric mixture of l-hydroxy-4-phenylperhydropyrido[2,l-c][l,4]oxazines 309 and 311, respectively. Similarly, diastereomeric mixtures of 8-substituted l-hydroxy-4-phenylperhydropyrido[2,l-c][l,4]oxazines were prepared (01EJOC2385). 

Dimethylphenylsilyl-2-propenylboronate 7 is more enantioselective (81-87% ee with achiral aldehydes) than the 2-[cyclohexyloxy(dimethyl)silyl] compound 8 (64-72% ee), and consequently the former generally gives better results especially in mismatched double asymmetric reactions. Nevertheless, the examples show that appreciable double diastereoselection may be achieved with both reagents in many cases. 

In platinum chemistry, cleavage of bis(silyl) compounds by HCl may be used [Eqs. (58), (59)] to generate monosilyl complexes 63). 

Difunctional reagents, for example the very cheap dimethyldichlorosilane 48, which is produced on a large technical scale, and the much more reactive and expensive dimethylsilyl bis(O-triflate) 49 [65-67] (Scheme 2.8) convert alcohols or phenols 11 in the presence of bases, for example triethylamine or DBU, into the silylated compounds 50. Thus 48 and 49 and other bifunctional reagents such as di-tert-butyldichlorosilane [68] or di(tert-butylsilyl)-bis(0-triflate) [69] and the subsequently described 51 and 52 combine two alcohols to silicon-tethered molecules 50, which can undergo interesting intramolecular reactions [70-74]. 

Reaction of tert-butyldimethylsilanol 85 a or tert-butyldiphenylsilanol 85 b, which are obtained on cleavage of O-silyl compounds, with SOCI2 in CHCI3, affords the desired re-usable chlorosilanes 86a and 86b in 39 and 81% yield, respectively [109] (Scheme 2.16). 

Whereas conversion of sulfoxides to the corresponding a-acyloxysulfides by acid anhydrides, for example acetic anhydride, the Pummerer reaction [1], has been known for quite a time, the conversion of sulfoxides with silylating reagents via the unstable intermediate O-silyl compounds to a-silyloxysulfides, the Sila-Pummerer reaction is a relatively new reaction, which has recently been reviewed [1—4-]. 

We also reported that CpFe(CO)2Me acts as a precursor for the Si-O-Si bond formation reaction from hydrosUane and DMF (Scheme 51)[ 166,167]. In this reaction, tertiary silanes and bis(silyl) compounds are converted into the corresponding disUox-anes and the polymers with (-R-Si-O- i)n backbone, respectively. 

Each of these couplings is inversely proportional to the cube of the distance between the atoms concerned, and all the dipolar couplings depend on the degree of orientation of the molecules. The ratios of couplings thus depend on the ratios of distances in the molecule, and from them the entire molecular structure, except for the overall size, may be determined. Studies of silyl compounds dissolved in cyanobiphenyl liquid crystals have yielded the following HSiH angles ... 

In each of these cases the angle is wider in solution than it is in the gas phase by about 2°. We believe that this is caused by weak interactions between the cyano groups of the solvent and the silyl groups, interactions which are comparable to those seen in many silyl compounds in the crystalline phase. 

First attempts to combine pyrolysis with in situ HMDS silylation of organic art materials were reported by Chiavari et al., who were successful in obtaining trimethylsilyl derivatives of fatty acids [52], amino acids [53] and carbohydrates [54]. The same authors also applied pyrolysis-silylation to the analysis of different kinds of natural resins and for each of them diagnostic silylated compounds were identified, even if many were difficult to assign precise structures [55],... 

For the silyl compounds (Table 27) high-quality calculated BDE values have also been included with the experimentally derived quantities. Here, the uncertainties and distribution of experimental values are larger than for the methyl compounds. The calculated BDEs in this work and corresponding comparison experience with the methyl compounds can, perhaps, be used to narrow some of the uncertainties in the silyl compounds. For almost all the germaniun, tin and lead compounds in Tables 28-30, the calculated BDEs are the only information available to date. 

Directed. s/ 3-benzylic C-H functionalization can lead to C-Si bond formation with both mono- and bis-silylated compounds obtained (Equations (53) and (54)). 

In the cathodic reduction of activated olefins, chlorosilanes also act as trapping agents of anionic intermediates. Nishiguchi and coworkers described the electrochemical reduction of a,/ -unsaturated esters, nitriles, and ketones in the presence of Me3SiCl using a reactive metal anode (Mg, Zn, Al) in an undivided cell to afford the silylated compounds [78]. This reaction provides a valuable method for the introduction of a silyl group into activated olefins. 

A classic paper by Baizer and Chruma [35] describes synthetic applications based on the reduction of allyl halides. Electrolyses of 4-bromo- and 4-chloro-2-butene can be employed for the allylation of acetone and benzaldehyde [36], and the reduction of allyl halides in the presence of trimethylchlorosilane affords silylated compounds [34]. 

These coupling constants are highly decreased if one considers 71 as a silyl compound with an agostic bond. Alternatively, if the hydride silylene description is chosen, the value of 7(Si-H) is increased in comparison with usually observed nonbonding values. 

The trialkylstannyl derivatives are obtained directly by reaction of tri-methyltin chloride with 2-lithiooxazole (87S693), but in the case of the silyl compounds an extra step is required, involving the base-catalyzed thermal ring closure of the silylated ring-opened oxazole (Scheme 81)(84CC258 87JOC3413). 

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