Construction of Unusual and Congested Polycyclic Structures via Benzannulated Enediynyl Alcohols Derived from Truxenone

Condensation between truxenone (8) and the lithium acetylide derived from 0.9, 2.5, and 5.0 equiv of
1-ethynyl-2-(phenylethynyl)benzene produced the corresponding benzannulated enediynyl alcohol 9, diol
14, and triol 16, respectively. On exposure of these alcohols to thionyl chloride, cascade cyclization
reactions occurred to furnish polycyclic compounds 13, 15, and 18 in a single operation. The unusual
architectures of these polycyclic compounds were established by NMR spectroscopy and X-ray structure
analyses.