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; C-3-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 D-3-symmetric molecular propeller.
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