Synthesis and Properties of 1,5-Dimethyltricyclo[3.3.0.0<sup>2,8</sup>]octane- and 1,5-Dimethyltetracyclo[3.3.0.0<sup>2,8</sup>0<sup>4,6</sup>]octane Derivatives
The synthesis of 1,5-dimethyltricyclo[3.3.0.02,8]octane-3,7-dione (2), 1,5-dimethyltetracyclo[3.3.0.02,804,6]-octane-3,7-dione (3), the corresponding dienes 5 and 6 as well as the mixed enones 13–15 is reported. Using He(I) photoelectron spectroscopy (PE) as a tool, a considerable interaction between the n orbitals on the O-atoms and the σ frame in 2 and 3 as well as of the double bonds in 5 and 6