Sterically congested in-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 A 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 A, significantly shorter than the ca. 1.54 A distances found in similar but uncongested molecules.
Song
Qiuling
Q
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
Ho
Douglas M
DM
Pascal
Robert A
RA