Evidence for Fully Conjugated Double‐Stranded Cycles

Abstract

A chain of circumstantial evidence for the existence of the first fully conjugated, double-stranded cycles is presented. The products have the structure of the belt-region of fullerene C(84)(D(2)) and carry either four hexyl chains or four phenyl groups. The unsubstituted parent cycle is also presented. The chain of evidence is mainly based on mass spectrometric analysis and trapping reactions, the latter being supported by quantum mechanical calculations. It is also of importance that the phenyl-substituted and unsubstituted products cannot undergo a [1,5] hydrogen shift, the only reasonable side-reaction that recently could not be excluded for the alkyl-substituted analogue. It is concluded that the fully aromatic targets truly exist in the gas phase. Whether they can be generated in solution under the applied conditions cannot yet be firmly decided; theoretical evidence speaks against.

Konjugierte Makrocyclen: Konzepte und Anwendungen

“…schen Leuchtdioden blaues Licht. [150] Schlüter und Mitarbeiter synthetisierten erstmals die vollständig konjugierten, doppelsträngigen Cyclen 198 a-c durch die Thermolyse von 197 a-c. [151] Die Bildung von 198 a,b wurde durch massenspektrometrische Analyse und Abfangreaktionen bestätigt.…”

Highly diastereoselective synthesis of a novel functionalized benzocyclotrimer

“…This reactive intermediate was captured by furan, acting as dienophile in a [4+2] cycloaddition (Scheme 1). [16][17][18][19][20][21][22][23][24][25] The resulting oxabicycle 4 was brominated according to a well-established radical-driven procedure, 14 which avoids…”

Synthetic Strategies of Carbon Nanobelts and Related Belt‐Shaped Polycyclic Aromatic Hydrocarbons

“…[21] Next they reported the synthesis of analogs 24 b (R = Ph) and 24 c (R = H) in the hope of observingt he corresponding aromatic belts 26 b and 26 c, since 1,5-hydrogen shifti snot possible in these two compounds. [22] Without isolating 25 b and 25 c,t hey eventually observed the corresponding aromatic belts 26 b and 26 c under matrix-assisted laser desorption/ionization (MALDI)c onditions by mass spectroscopy.I nt his example, the macrocyclization step and the belt-formings tep are completed within as ingle step, namely the Diels-Alderr eaction in which 24 is formed. However,t he final strain-inducing step seems quite tricky in this system as direct acid-mediated dehydration of 24 a could only yield adoubly dehydrated product.…”