Biphenyl-2-ylethylenes react with (4-BrC6H4)3N.+SbC16-to give the radical cation of the electrocyclization product which initiates a protic catalysis t o the related fluorenes or, in presence of 2,6-di-t-butylpyridine or water, lead stoicheiometrically t o phenanthrenes; with photochemical oxidants only phenanthrenes or 9,lO-dihydrophenanthrenes are obtained, with an efficiency related to the polarity of the solvent and the relative energies of the triplet donor and of the radical ion pair.
Bromination of benzyltrimethylsilane in carbon tetrachloride yields the bromobenzyltrimethylsilanes (II), whereas in acetonitrile, benzyl bromide (III), and bromotrimethylsilane (IV) are obtained.
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