Through-bond interaction via cyclobutane relay orbitals as a means of extending conjugation. Synthesis of tricyclo[5.5.0.02,8]dodecatetraene, tricyclo[5.3.0.02,8]deca-3,5,9-triene, and 9,10-dimethylenetricyclo[5.3.0.02,8]deca-3,5-diene