En route to archimedene: total synthesis of C3h-symmetric [7]phenylene.
[reaction: see text] The total synthesis of C(3)(h)-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(3)(h) isomer. The molecule constitutes the largest substructure of archimedene hitherto synthesized.
Bruns
Dirk
D
Center for New Directions in Organic Synthesis, Department of Chemistry, University of California at Berkeley, Berkeley, California 94720-1460, USA.
Miura
Hirokazu
H
Vollhardt
K Peter C
KP
Stanger
Amnon
A