A pentacene with a 144 degrees twist.
9,10,11,20,21,22-Hexaphenyltetrabenzo[a,c,l,n]pentacene (1) was prepared by the reaction of 1,3-diphenylphenanthro[9,10-c]furan with the bisaryne equivalent generated from 1,2,4,5-tetrabromo-3,6-diphenylbenzene in the presence of n-butyllithium, followed by deoxygenation of the double adduct with low-valent titanium. The X-ray structure of 1 shows it to be the most highly twisted polycyclic aromatic hydrocarbon known, with an end-to-end twist of 143.6 degrees . Compound 1 was resolved by chromatography on a chiral support, and the pure enantiomers have specific rotations in excess of 7000 degrees , but the molecule racemizes slowly at 25 degrees C (t1/2 = 9.3 h, DeltaGrac = 23.8 kcal/mol).
Lu
Jun
J
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
Ho
Douglas M
DM
Vogelaar
Nancy J
NJ
Kraml
Christina M
CM
Pascal
Robert A
RA
D001969:Bromobenzenes / Q000737:chemistry; D008968:Molecular Conformation; D011084:Polycyclic Aromatic Hydrocarbons / Q000138:chemical synthesis / Q000737:chemistry*
D001969:Bromobenzenes; D011084:Polycyclic Aromatic Hydrocarbons