Restricted Rotation Involving the Tetrahedral Carbon. XXXIX. 9-(2-Methoxy-1-methylethyl)triptycene Derivatives

Article abstract of DOI:10.1246/bcsj.54.2383

9-(2-Methoxy-1-methylethyl)triptycenes were prepared from 9-(2-methoxy-1-methylethyl)anthracene and corresponding benzynes to examine the feasibility of isolating rotational isomers of 9-isopropyltriptycene derivatives at room temperature.They afforded crystalline ap forms which underwent internal rotation with activation energies of ca. 23 kcal/mol. 9-(2-Acetoxy-1-methylethyl)-1,2,3,4-tetrachlorotriptycene gave similar results.Based on the results, the barrier to rotation of 9-isopropyl-1,2,3,4-tetrabromotriptycene was reexamined to show that it must be corrected as 23.5 kcal/mol at 175 deg C.