Directed metalation silicon protection

Directed ortho Metalation (DoM). The synthesis of the alkaloid schumarmiophytine requires a silicon protection of the more reactive ortho 0-carbamate site to set the stage for the key step, a remote anionic Fries rearrangement that results in a pyridine ring carbamoyl translocation (eq 48). ... 

Titanium Silicides. The titanium—silicon system includes Ti Si, Ti Si, TiSi, and TiSi (154). Physical properties are summarized in Table 18. Direct synthesis by heating the elements in vacuo or in a protective atmosphere is possible. In the latter case, it is convenient to use titanium hydride instead of titanium metal. Other preparative methods include high temperature electrolysis of molten salt baths containing titanium dioxide and alkalifluorosiUcate (155) reaction of TiCl, SiCl, and H2 at ca 1150°C, using appropriate reactant quantities for both TiSi and TiSi2 (156) and, for Ti Si, reaction between titanium dioxide and calcium siUcide at ca 1200°C, followed by dissolution of excess lime and calcium siUcate in acetic acid. 

In the case of boundary layer lubrication, in which the adsorption of mono-molecular films is required, the best protection is provided by materials such as fatty acids and soaps that can adsorb strongly at the surface to form a solid condensed film. Less durable but effective protection can be obtained with polar groups such as alcohols, thiols, or amines. The least effective protection is obtained with simple hydrocarbons that adsorb more or less randomly and through dispersion forces alone. For adsorbed monomolecular films, best results are obtained when the hydrocarbon tail has at least 14 carbons. In some cases fluorinated carboxylic acids and silicones may provide a lower initial coefficient of friction, but their weaker lateral interaction sometimes results in a less durable surface film that melts at a lower temperature, ultimately resulting in less overall protection. If a polar lubricant can form a direct chemical bond to the surface, as in the formation of metal soaps, even better results can be expected. 

It has been demonstrated that polyferrocenylsilanes possess low plasma etch rates, which can be attributed to the formation of a protective layer of involatile iron and silicon compounds. This property has been exploited with PFS block copolymers self-assembled into micelles or phase-separated thin films to deposit patterned ceramics as well as for pattern transfer to the substrate. In our research, we are interested in the direct formation of high metal content magnetic ceramic films by RIE treatment of Co-PFS in the presence of a secondary magnetic field. ... 

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