Silanes with aromatic bridges

There are several limitations on these methods with regard to the heteroatom involved. Reaction of the tin heterocycle with NBS results in cleavage of the aromatic-tin bonds to give o,o -dibromobibenzyl (81). Reaction of the tin heterocycle with DDQ resulted only in products of heteroatom elimination (81). Attempts to generate a silicon heterocycle with a functional group on the Si atom have failed to produce the unsaturated system (XVII). Dehydrobromination reactions of the silane afford highly colored reaction products but no isolable identifiable monomer. It is probable that the dehydrobromination reaction occurs not only at the ethylene bridge but also by transannular elimination. 

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