Addition of one mole of phenyllithium to bicyclo[3,3.1]nonane-2,6-dion
e (5) affords the hydroxy ketone 6 besides small amounts of the known
diol 7. Dehydration of this mixture by sulfuric acid in acetic acid yi
elds the unsaturated ketone 8 and the diene 1 which are separated by c
hromatography. Wolff-Kishner reduction of 8 furnished the hydrocarbon
2. In the same way, the known ketones exo- and endo-10 are converted i
nto 4. The preferential formation of the less stable endo-10 is interp
reted in terms of the relative stability of the conformations required
in the intramolecular aldol reaction of diketone 9. The conformations
of 4, 8, exo- and endo-10 are determined by X-ray diffraction analyse
s. Vicinal proton coupling constants are calculated from torsional ang
les and compared to those determined in solutions by high-field NMR sp
ectroscopy.