Syntheses of and Restricted Csp3–Csp2 Bond Rotation in Triptycenes That Carry C4-Olefinic Substituent at 9-Position

Triptycene derivatives that carry C4-olefinic substituents at the 9-position, in which the olefin is connected to C(9) through an sp2 carbon, are synthesized. Their dynamic behaviors, as observed by dynamic NMR technique, are discussed on the basis of the results of MM2 calculations. The barrier to rotation of the olefinic groups is higher when there is a methyl group which directs inside relative to the triptycene skeleton, than the cases where no such a methyl group exists.