Silicon organosilicon compounds

Our discussion to this point has been limited to molecules m which the chirality center IS carbon Atoms other than carbon may also be chirality centers Silicon like carbon has a tetrahedral arrangement of bonds when it bears four substituents A large number of organosilicon compounds m which silicon bears four different groups have been resolved into their enantiomers... 

H. W. Post, Silicones and Other Organosilicon Compounds, Reinhold, New York, 1949. 

The possibility of the existence of organosilicone compounds was first predicted by Dumas in 1840, and in 1857 Buff and Wohler found the substance now known to be trichlorosilane by passing hydrochloric acid gas over a heated mixture of silicone and carbon. In 1863 Friedel and Crafts prepared tetraethylsilane by reacting zinc diethyl with silicon tetrachloride. 

So far only a few examples of the uses of organosilicon compounds in cross-couplings have been published. Noteworthy is the smooth reaction with a sterically hindered substrate (87).295 The synthesis of the alkaloid nitidine included a cross-coupling step using an alkenylsilane (88),296 while the syntheses of some antitumor agents involved the alkenylation of unprotected iodouracyls using alkenyl-silicon species.297... 

Scheme 5. Reactions of silicon tetrachloride and organosilicon compounds with stable nucleophilic carbenes.

Silicon is no longer an exotic element in electroorganic chemistry. The electrochemical behaviour of organosilicon compounds is easily understood, because the following concepts help us to appreciate their unique properties. 

It is hoped that the examples and the accompanying mechanistic discussions of electrochemical reactions of organosilicon compounds shown in this review will provide a guide to the potential utility of such reactions in organic synthesis and to the development of new electroorganic chemistry based on the unique properties of silicon. 

Although carbon and silicon both belong to the same group of periodic table and many of the silicon compounds resemble carbon compounds, but the chemical reactivity of silicon in organosilicon compounds is more comparable to that of hydrogen because many nucleophilic displacements at... 

The reactivity of organosilicon compounds is influenced by the more electropositive nature of the silicon atom as compared to carbon and hydrogen and also by the availability of empty d orbitals, although the latter point has now become controversial. On this basis Si-0 and Si-F bonds are stronger than the C-0 and C-F bonds. The Si-H bonds are weaker than C-C and H-C bonds. 

In 1976 W.C. Still (J. Org. Chem. 41, 3063-41) discovered Me3SiLi and in the same year RB. Dervan and MA Shippey (J. Awer Chem. Soe, 98, 1265-1267, 1976) discovered Me3SiK which are silicon nucleophiles and both of which promised to be very useful for preparing organosilicon compounds. 

Many unsaturated organosilicon compounds undergo facile electrophilic substitution reactions. The arylsilanes also appear to be activated towards electrophilic substitution. Substitution normally takes place exclusively at the site of silicon atom. 

Some Applications of Organosilicon Compounds to Organic Synthesis Why Silicon Compounds are Reactive... 

Organosilicon compounds are widely used in organic synthesis. The understanding of the structure and properties of the intermediates involved in their reactions is a prerequisite for further development and optimization of useful synthetic transformations involving silicon substituted compounds. Trialky lsilyl-substituted carbocations are particularly... 

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