The object of the first part of this thesis was to determine whether a bridgehead double bond is more stable when located in the larger or smaller bridge of a bicycle. For this purpose a unique Bredt compound (A) was prepared. This is the only verified example of an aromatic ring located on two bridges of a bicycle. The compound was examined (1H n. m. r., 13C n. m. r., u.v., and Raman) for evidence of bond-fixation (Mills-Nixon effect) within the aromatic ring. An x-ray analysis was not possible, but other workers have made available molecular mechanics calculations on (A), Although there was spectroscopic evidence that the benzene ring is non-planar and molecular mechanics calculations show that some bonds are unusually short, there was no indication that it is other than aromatic. On the basis of the calculations, it would appear that, contrary to published evidence, the bridgehead double bond is more stable when located in the smaller bridge. The preferred conformation of the molecule, as deduced spectroscopically, was in agreement with that calculated for (A). The second part of the thesis describes an attempt to use ring annulation-scission methods to synthesise macrocycles from available five and six membered rings. The necessary tricyclic (B) and benzo-tricyclic (C) precursors were obtained, but various attempts to cleave the bridges of these compounds proved more difficult than expected. Thus, the amide derived from (B) by Beckmann rearrangement of its oxime, could be hydrolysed, but rapidly recyclised on standing
