En route to archimedene:: Total synthesis of C3h-symmetric [7]phenylene

[GRAPHICS] The total synthesis of C-3h-symmetric [7]phenylene has been accomplished by triple cobalt-catalyzed cycloisomerization of an appropriate nonayne. Its spectral data are in accord with the expectations for a triply angularly fused system, but its calculated heat of formation suggests the presence of a destabilizing sigma effect relative to its D-3h isomer. The molecule constitutes the largest substructure of archimedene hitherto synthesized.