Tribenzodecacyclene and Hexabenzodecacyclene

High-temperature,
TiCl4-catalyzed, triple aldol condensations
of aceanthrenone 5 and acenaphthacenone 6 gave tribenzodecacyclene 3 and hexabenzodecacyclene 4, respectively, in yields of 16 and 0.8%, respectively. Compound 3 is a red, crystalline solid that is stable under ordinary
conditions; its X-ray structure reveals it to be a strongly pitched, C3-symmetric, molecular propeller. In contrast,
the more highly strained compound 4 is a blue-black solid
whose solutions are unstable to air and light. Its simple NMR spectra,
as well as HDFT calculations, indicate that it is a D3-symmetric molecular propeller.