Die charakteristischen Eigenschaften homoaromatischer Systeme

Abstract

Verbindungen mit homoaromatischen Eigenschaften sind nach wie vor ein auflerordentlich interessantes Gebiet der Chemie. Derzeit wird u. a. versucht, das AusmaR der weitreichenden Delokalisierung von Elektronen experimentell zu bestimmen, die Wechselwirkungen in Molekiilen mit zwei oder mehr isolierenden Atomen zu ermitteln und energetische sowie geometrische Eigenschaften der homoaromatischen Systeme theoretisch abzuschatzen. In diesem Aufsatz werden in erster Linie neuere spektroskopische und strukturelle Befunde kritisch besprochen; daneben werden die Reaktionen analysiert, die den Zugang zu homoaromatischen Ionen ermoglichen. Ausfuhrlich diskutiert werden mono-, bis-und trishomoaromatische Systeme, und zwar getrennt nach kationischen, anionischen und neutralen Spezies. Zuvor wird kurz die Orbitaliiberlappung in diesen Verbindungen dargestellt.

Unusual Rearrangements in the C12H12‐Manifold 1,5,9‐Cyclododecatriyne, 1,2:3,4:5,6‐Tricyclobutabenzene, Hexaradialene

“…cis,cis,cis-l,5,9-cyclododecatriene was obtained by the method of Untch and Martin," with the following exception: it was found that elimination with potassium r-butoxide in tbutanol gave a faster and cleaner elimination to the tribromocyclododecatrienes in high yield; this was therefore the method of choice for this dehydrobromination. I,2,5,6,9,cis, In a typical experiment, 109 of triene 9 (62 mmol) was dissolved in about 150 mL of CCI. in a 500-mL round-bottom flask.…”

“…The crude material was used without further purification in the next step. Z,Z,5,5, A portion of the crude mixture of hexabromocyclododecanes (6.8 g, 10.6 mmol) was dissolved in dry THF (20 mL) under nitrogen. A solution of sodium ethoxide in ethanol [prepared by adding 0.73 g (31.7 mmol) of sodium to 50 mL of dry EtOH) was added dropwise over about 30 min.…”

“…(C'2H15Br,) C, H, Br. I,5, Sodium (0.7 g, 30 mmol) was dissolved under nitrogen in methanol (150 mL). Water (about 0.5 mL distilled) was then added.…”

“…Attempted Reaction of 1,5, with TCNE Triyne 1 (10 mg, 0.064 mmol) TCNE (38 mg, 0.30 rnmol), and o-xylene (1 mL) were placed in a thick walled glass tube, degassed, and sealed under vacuum. The reaction mixture was then heated in a 225°oil bath for 9.5 h leading to complete polymerization.…”

“…FinalIy 1 and 2, respectively, could be regarded as precursors to the elusive radialene 3, a molecule which, despite its olefinic Kekule-structure, might maintain a certain degree of aromatic delocalization, and could function as a precursor to another molecule of considerable current theoretical interest, the "superphane" 5. 1,5,. SYN'I'HFSIS AND THERMOLYSIS IN THE CONDENSED PHASS imple HMO calculations' on 1 reveal at best weak (ca.…”