Photodehydrocyclizations of stilbene-like compounds VIII: Synthesis of hexaheliceno[3,4-c]hexahelicene
The synthesis of a new double helicene, hexaheliceno[3,4-c]hexahelicene, has been described. Of two possible diastereomers only one has been obtained. Presumably the product has the racemic configuration but this assignment is not yet definite.
A Naphtho-Fused Double [7]Helicene from a Maleate-Bridged Chrysene Trimer.
Perkin condensation of chrysenyl-6-acetic acid with chrysenylene-6,12-diglyoxylic acid followed by in situ esterification gives a bismaleate, whose conjugated stilbene moieties are efficiently shielded against intermolecular condensations and undergo iodine-catalyzed oxidative photocyclization in toluene without the need for high dilution. The concentration is limited by the low solubility of the flexible bismaleate at room temperature. The so-obtained double [7]helicene crystallizes in a nonchiral meso form. It is notably more soluble than its flexible precursor because it cannot fold to optimize π-π stacking.
Untersuchungen in der Cyclobutanreihe, III Über Benzocyclobutadien†
Das bei der Behandlung des 1.2-Dibrom-benzocyclobutens mit Lithiumamalgam in ather. Losung entstehende unbestandige Benzocyclobutadien wurde in Form eines Adduktes mit Cyclopentadien gefast. Fur diese Verbindung wird die Struktur des 1.4-Endomethylen-1.4.11.12-tetrahydro-diphenylens (III) wahrscheinlich gemacht.