Silanes with nitrobenzenes

Compounds 4 and 5 were synthesized by treatment of trimethoxy(morpholiniomethyl)silane with two mole equivalents of l,2-dihydroxy-4-nitrobenzene and 3,5-di-tbutyl-l,2-dihydroxybenzene, respeetively, in acetonitrile at room temperature (Scheme 1). 

The six-position may be functionalized by electrophilic aromatic substitution. Either bromination (Br2/CH2Cl2/-5°) acetylation (acetyl chloride, aluminum chloride, nitrobenzene) " or chloromethylation (chloromethyl methyl ether, stannic chloride, -60°) " affords the 6,6 -disubstituted product. It should also be noted that treatment of the acetyl derivative with KOBr in THF affords the carboxylic acid in 84% yield. The brominated crown may then be metallated (n-BuLi) and treated with an electrophile to form a chain-extender. To this end, Cram has utilized both ethylene oxide " and dichlorodimethyl-silane in the conversion of bis-binaphthyl crowns into polymer-bound resolving agents. The acetylation/oxidation sequence is illustrated in Eq. (3.54). 

It is clear that the ionizing power of the solvent used is important in many of these reductions. When 2,4,6-trimethylbenzyl chloride is heated with diphenylsi-lane in nitrobenzene at temperatures as high as 130°, no isodurene is formed.193 Not unexpectedly, the same lack of reactivity is reported for a series of benzyl fluorides, chlorides, and bromides substituted in the para position with nitro or methyl groups or hydrogen when they are heated in nitrobenzene solutions with triethylsilane, triethoxy silane, or diphenylsilane.193... 

An apparatus has been developed392 for the analysis of a mixture containing tri-chlorosilane, methyldichlorosilane, silicon tetrachloride, trimethylchlorosilane, di-methyldichlorosilane and methyltrichlorosilane by gas-liquid chromatography on a column of nitrobenzene supported on Celite 545. The column is eluted with nitrogen and the emergent gas is absorbed in flowing 0.01 N potassium ohloride. Hydrolysis of the silanes yields hydrochloric acid which alters the electrical resistance of the potassium chloride solution and this permits quantitative analysis of the silane mixture. 

The separation and determination has been carried out408,409 of dichloromethylvinyl-silanes and the chlorovinylsilane and impurities therein. Compounds in trichlorovinylsil-ane were separated on a column of silicone elastomer supported on Celite. For impurities in trichloromethylvinylsilane, best results were obtained with a column of nitrobenzene supported on kieselguhr. 

Incorporating aromatic silane functions into aromatic polyamides can also improve solubility [45], and was shown recently by Vernekar et al. [38] with polymers 23. These polyamides from 3,3 or 4,4 [suIfonylbis-(4,l-phenyleneoxy)] bisbenzenamine have higher solubility than those from bis(4-aminophenyl)ether. They are soluble in amide solvents, pyridine and w-cresol, and some in THF and nitrobenzene. They also have a high Tj in the range of 477-513 °C, and a Tg in the range of 209-246 °C. 

Figure 12.3 ElectrcxJeposition of silane at the electrode/nitrobenzene/aqueous electrolyte three-phase junction. (Reproduced with permission from Ref. [15].)...

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