Regiochemical Control in Triptycene Formation—An Exercise in Subtle Balancing Multiple Factors

Reactions between 1,8‐dichloroanthracenes with substituents in position 10 and ortho‐chloroaryne afford mixtures of 1,8,13‐ (syn) and 1,8,16‐trichlorotriptycenes (anti). The syn/anti ratio is dependent on these substituents. Electropositive substituents like SiMe(3) and GeMe(3) lead to preferred formation of the syn‐isomer, whereas CMe(3) groups exclusively afford the anti‐isomer. Different quantum chemical calculations including location of transition states give conflicting results, but indicate the importance of dispersion forces for an at least qualitative prediction of results. The syn‐trichlorotriptycenes with SiMe(3) and GeMe(3) substituents were characterized by using NMR spectroscopy, mass spectrometry, and X‐ray diffraction experiments.