Polyethylated Triptycene Derivatives

The octaethyl triptycenes 7 and 8 were synthesized by Diels−Alder reaction of the octaethylanthracene 4 with the corresponding benzynes. Low-temperature NMR spectra of 7 and 8 are consistent with the presence of the fully alternated conformation “a” of C 2 symmetry. However, in the determined crystal structures, the compounds adopt a higher energy conformation with a pair of vicinal ethyls oriented in the same direction.