Formation of pentaorganostannates from Bis(2-bromo-2′-biphenyl) stannanes and tert-butyllithium upon substitution of alkyl and aryl groups on tin atoms

The reaction, of bis(2-brom.o-2'-biphenyl)stannanes 1 with tert-butyllithium in the presence of diaryl- and dialkyldichlorostannanes leads to the extrusion of aryl and alkyl groups on the tin atom, affording 9-stannafluorene derivatives bearing biphenyl groups. The intermediates of the reactions were assigned to the corresponding pentaorganostannates, which were characterized by NMR spectroscopy. Unexpectedly, the dissociation of the aryl and alkyl groups from the tin atoms in intramolecular nucleophillc substitution reactions was preferable to that of chloride ions in intermolecular nucleophilic substitution reactions.