title: Polyphenyl macrocyclic oligophenylenes.
abstract: The Diels-Alder reaction of tribenzohexadehydro[12]annulene (12) and 3,4-diphenyl-2,5-dimethylcyclopentadienone (13) at 300 degrees C gave the triple adduct 2,3,10,11,18,19-hexaphenyl-1,4,9,12,17,20-hexamethylhexa-o-phenylene (6b) in 13% yield. NMR and X-ray analysis indicated that 6b adopts a screw conformation (C2) rather than a crown conformation (C3), and computational studies seem to rule out any interconversion of the two. Palladium-catalyzed coupling of 1,2-bis(4-bromophenyl)-3,4,5,6-tetraphenylbenzene (17) and the corresponding bis(boronic acid) 18 gave a mixture of linear and cyclic oligomers of hexaphenylbenzene containing two to six hexaphenylbenzene subunits. A macrocyclic tetramer was isolated from this mixture in 5% yield, and X-ray analysis showed it to be the "supertetraphenylene" 7 (C168H112) that contains a large central cavity and packs to form highly solvated, porous crystals. The difficulties encountered in the purification of 7 led to the development of alternative, more highly selective syntheses that give the pure macrocycle more easily but in essentially the same overall yield.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Qiuling
authors.initials: Q
authors.lastname: Song
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Lebeis
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Shen
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Ho
authors.forename: Robert A
authors.initials: RA
authors.lastname: Pascal