RESTRICTED ROTATION INVOLVING THE TETRAHEDRAL CARBON. L. ROTAMER DISTRIBUTIONS AND ROTATIONAL BARRIERS IN SOME 9-(1-METHOXYETHYL)TRIPTYCENE DERIVATIVES.

Article abstract of DOI:10.1246/bcsj.56.3023

1,4-Dimethyl- and 1,2,3,4-tetrahalo-9-(1-methoxyethyl)triptycenes were synthesized by reactions of 9-(1-methoxyethyl)anthracene with appropriate benzynes. Rotamer distributions and rotational barriers about the bridgehead-to-substituent bond were studied by NMR spectroscopy. Rotamer distributions are governed mainly by the steric effect; the major rotamer is assigned to sc*(S*), the minor one to ap, and the third one found only in the tetrafluoro derivative to sc*(R*). *). Rotational barriers are 21-23 kcal mol** minus **1 which are slightly lower than those for the corresponding 9-isopropyltriptycenes.