in- and out-Cyclophanes Bearing Non-Hydrogen Bridgehead Substituents

The syntheses of several cyclophanes containing a triaryl(element) "top" poised above a trisubstituted benzene "base" were carried out to install a non-hydrogen atom as a substituent on a bridgehead with an inwardly directed geometry. Most significantly, the tribenzo 6-fluoro-6-sila-2,10,19-trithia[5(6,14)][11]metacyclophane 2 was prepared by condensation of tris[2-(bromomethyl)phenyl]fluorosilane and 1,3,5-tris(mercaptomethyl)benzene in 0.4% yield. The X-ray structure of 2 shows that the cyclophane adopts an in-configuration; i.e., the fluorine atom is on the interior of the macrocycle and only 2.8 Å from the center of the basal aromatic ring. Compound 2 is one of only a very few molecules to contain a non-hydrogen in-atom, and the in-fluorosilane of 2 is the largest in-functional group to have been installed in any molecule. Similar attempts to prepare an in-phosphine oxide were unsuccessful, although the corresponding in-phosphines were prepared, and an attempt to prepare an in-methylsilane led instead to the corresponding out-isomer.