Silicon trifluoromethyl compounds

Previously, trifluorosilyl groups have been bound to phosphorus (40) and silicon via the SiF (g), fluorine-bond insertion-mechanism (41). The new compound HgCSiFs) is readily hydrolyzed, but it can be stored for long periods of time in an inert atmosphere. It is a volatile, white solid that is stable up to at least 80°C. The preparation of bis(trifluoro-silyDmercury, of course, raises the possibility of (a) synthesis of the complete series of trifluorosilyl, "silametallic compounds, as had previously been done for bis(trifluoromethyl)mercury by using conventional syntheses, and (b) transfer reactions similar to those in Section II, as well as (c) further exploration of the metal-vapor approach. The compound Hg(SiF.,)j appears also to be a convenient source of difluoro-silane upon thermal decomposition, analogous to bis(trifluoromethyl)-mercury ... 

On the basis of differences in electronegativity, tlie C - Si bond possesses 12% ionic character. Silicon is the positive end and carbon is the negative end of the dipole. Trimethyl(trifliioro-methyl)silane is thus a reagent for introducing the trifluoromethyl group into carbonyl compounds (aldehydes, ketones, enoncs). ... 

Trimethyl(trifluoromethyl)silane can be converted into tributyl(trifluoromethyl)tin (40) in quantitative yield by treatment with bis(tributyltin) oxide in tetrahydrofuran under fluoride ion initiation. Tributyl(trifluoromethyl)tin readily trifluoromethylates disilyl sulfides at room temperature giving the corresponding trifluoromethylated di- and trialkylsilancs 41 in high yields. This method provides a new approach for the preparation of silicon-based trifluoro-methylating reagents via transtrifluoromethylation of compounds containing Si — S bonds. 

The bromotrifluoromethanc/tris(dielhylamino)phosphane system can be used as a reagent for the introduction of a trifluoromethyl group into various silicon compounds.30... 

Trifluoromethyl Silicon Compounds with Geminal Nitrogen Donor Centers... 

Nucleophilic addition of the trifluoromethyl group to aldehydes, ketones and other carbonyl compounds leads primarily to the corresponding trimethylsilyl ether this must subsequently be hydrolyzed to the alcohol. Because typical reaction conditions are very mild, the method is widely applicable, even for sensitive substrates. In contrast with most other methods, fluoride-induced perfluoroalkylation via silicon compounds also works for enolizable carbonyl compounds. With c(, -un-saturated substrates 1,2-addition directly to the carbonyl group is strongly preferred [64b]. If the oxygen is coordinated to a bulky Lewis acid, for example aluminum tri(2,6-bis(tert-butyl)phenoxide (ATPH), the 1,4-addition products are obtained selectively [73f] (Scheme 2.128). 

Related spiro compounds, (13) and (9), are made differently from bis(trifluoromethyl)chloro-iodinane or silicon tetrafluoride, respectively, and dilithiated hexfluorocumyl alcohol <81JOC1049,... 

TBAF-assisted Trifluoromethylation, Perfluoroalkylation, and Polyfluoroalkoxylation. TBAF combines with TMSCF3 to form nucleophilic trifluoromethyl anion equivalents. The precise structure of this nucleophile is unknown, although it is likely that a pentacoordinate silicon intermediate is involved. The TBAF/TMSCF3 combination leads to smooth trifluoromethylation of aldehydes,ketones, esters, imines, nitroso compounds, a-ketoesters, Q -ketoamides (eq and... 

In view of the beneficial influence of silicon for the C-0 bond forming reactions, we have investigated silicon reagents for utility in C-C forming processes for fluorocarbon syntheses. Perfluoroalkylsilanes had been prepared but had not been utilized to synthetic advantage in this area[11]. Trifluoromethylsilanes react with aldehydes to give trifluoromethyl-substituted compounds[ ]. 

On the other hand when 3,5-bis(trifluoromethyl)- was used instead of 3,5-dimethylpyrazole, compound 2 (Fig. 1), a derivative of the hydrogen-rich SiHiCh, could be isolated and characterized by X-ray analysis. The silicon atom is additionally stabilized by two tetrahydrofuran molecules to achieve an overall octahedral coordination, which is most probably due to the nature of the electron-withdrawing pyrazolyl ligands. 

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