Reagents silicon

For other reactions of allylic silanes, look under the functional group introduced see also page 386, Section 21 and page 591, Section 5. 

RX (R=ailylic, benzylic X = halogen, OR), TiCL ArCH2SiMe3, VO(OEt)CI2 (E = CH2Ar) 

RN02 (R = ailylic, benzylic), SnCL AiCH2S02Ph, EtAlQj 

R Me3Si0C(MeXNHCH0)CO2Me, MejSiOTf [E=C(MeXNHCHO)C02Me] SL 451 (1992) JOC 58 3259 (1993) 

RN02 (R = allylic, benzylic), SnCl4 AiCH2S02Ph, EtAlCl2 

Me3SiOC(Me)(NHCHO)C02Me, Me3SiOTf [E = C(Me)(NHCHO)C02Me] 

Ac0CR(NHCOMe)CO2Et, BF3OEt2 [E=CR(NHC0Me)CO2Et] 

ClCH(NHC02Me)C02Me, SnCl4 [E=CH(NHC02Me)C02Me 

MeOCH(NHC02R)CONR2, HCO2H or BF3 OEt2 [E=CH(NHC02R)CONR2] JOC 57 6769 (1992) 

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W. P. Weber, Silicon Reagents for Organic Synthesis, Springer-Verlag, New York, 1983, pp. 255-272. 

A. W P. Jarvie, Organomet Chem. Rev., Sect A 6 153 (1970) W. P. Webei Silicon Reagents for Organic Synthesis, Springer-Verlag, Berlin, 1983 E. W Colvin, Silicon in Organic Synthesis, Butterworths, London, 1981. 

The structurally simplest silicon reagent that has been used to reduce sulphoxides is the carbene analog, dimethylsilylene (Me2Si )29. This molecule was used as a mechanistic probe and did not appear to be useful synthetically. Other silanes that have been used to reduce sulphoxides include iodotrimethylsilane, which is selective but unstable, and chlorotrimethylsilane in the presence of sodium iodide, which is easy to use, but is unselective since it cleaves esters, lactones and ethers it also converts alcohols into iodides. To circumvent these complications, Olah30 has developed the use of methyltrichlorosilane, again in the presence of sodium iodide, in dry acetonitrile (equation 8). A standard range of sulphoxides was reduced under mild conditions, with yields between 80 and 95% and with a simple workup process. The mechanism for the reaction is probably very similar to that given in equation (6), if the tricoordinate boron atoms in this reaction scheme are replaced... 

Tetravalent silicon reagents are less suitable for transient protection of any hydroxyl groups present, because the resulting activated oligomeric or polymeric intermediates cannot be defined. It can, furthermore, be expected that any derivatives utilizing tetravalent silicon are much more polar and less lipophilic than... 

Because allyltrimethylsilane 82 or benzyltrimethylsilane 83 can be regarded as combinations of the hard trimethylsilyl cation and the soff allyl or benzyl anions, pyridine N-oxide 860 reacts with excess 82 or 83 in the presence of catalytic amounts of tetrabutylammonium fluoride di- or trihydrate in THF to give 2-allyl-or 2-benzylpyridines 948 and 950 [60]. The general reaction of silicon reagents such as 82 and 83 or of trimethylsilyl cyanide 18 with fluoride to generate allyl or... 

All these silicon reagents which activate metal surfaces are also Lewis acids, which can also contribute as such to the acceleration of any of the subsequently discussed reactions, because of their inherent Lewis acid properties. 

E. W. Colvin, Silicon Reagents in Organic Synthesis, Academic Press, London, 1988. I. Fleming, J. Dunogves, and R. Smithers, Org. React., 37, 57 (1989). 

Weber WP (1983) Silicon reagents for organic synthesis. Springer, Berlin Heidelberg New York Colvin EW (1981) Silicon in organic synthesis. Butterworths, London... 

As shown by the obtained products, the reaction is highly cA-stereospecific. The utility of this method is evident in view of the extensive use of unsaturated silicon reagents in organic synthesis. ... 

Colviu, E. W. Silicon Reagents in Organic Synthesis, p. 7. Academic Press, Loudou, 1988. 

Only one example of electrophilic behavior of silicon-stabilized lithiooxiranes is reported. Intermolecular C—Li insertion followed by Li20 elimination occurs by raising the temperature, and ( ) vinylsilanes are obtained stereoselectively (Scheme 80). Reaction of lithiooxiranes with aluminum , zirconium and silicon reagents leads to the corresponding ate complexes, which undergo 1,2-metallate rearrangements. 

A method using dual activation has been developed in which a Lewis acid activates the aldehyde with concomitant nucleophilic activation of the allylic silicon reagent with fluoride anion. Thus, by using a BINOL-based titanium... 

Colvin, E. U. Silicon in Organic Synthesis " Butterworths London, 1981 Weber, W. P. "Silicon Reagents for Organic Synthesis " Springer-Verlag Berlin, 1983. 

Alkynes, and Arenes, 1985 Paul N. Rylander, Hydrogenation Methods, 1985 Ernest W. Colvin, Silicon Reagents in Organic Synthesis, 1988 Andrew Pelter, Keith Smith and Herbert C. Brown, Borane Reagents, 1988 Basil Wakefield, Organolithium Methods, 1988... 

Iodomethyltrimethylsilane has been used previously for this reaction (9, 444-445), but the tin reagent (1) is at least 600 times more reactive than the silicon reagent. Furthermore, fluoride-induced desulfonylstannylation is much faster than desulfonylsilylation, probably because a C-Sn bond is weaker than a C-Si bond. 

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