Sterically Congested <i>in</i>-Methylcyclophanes

The crowded in-methylcyclophane 9 was prepared by condensation of 1,8,13-tris(bromomethyl)-9-methyltriptycene and 1,3,5-tris(mercaptomethyl)benzene under high dilution conditions. Oxidation of 9 gave the highly crystalline trisulfone 10, and its X-ray structure was determined. The in-methyl carbon atoms of the two independent molecules in the structure are only 2.90 and 2.87 Å from the centroid of the basal aromatic ring, the closest such contacts ever observed. In addition, the C−CH3 bonds in these cyclophanes are compressed; the two independent bond distances are 1.475 and 1.495 Å, significantly shorter than the ca. 1.54 Å distances found in similar but uncongested molecules.