ISSN:
1434-4475
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract A comparison of structural data of bent aromatic molecules demonstrates the existence of two discernible boat forms of the benzene ring, which can be described formally in terms of 1–4 or 2–6/3–5 foldings, resp. While in 3-[1,3],6°-[1,3,4,6],9°-[1,3]tribenzaspiro[5.5]undecaphane (triple layered [2.2]metacyclophane) (7) the peripheral benzene rings adopt a boat conformation, the shape of the central ring is chairlike. This was concluded by NMR-spectroscopical methods from the constancy of the torsional angles of the bridges compared with the isomer6 together with structural considerations. Therefore the isomer ratio6∶7 should reflect to a significant extent the relative stabilities of boat and chair shaped benzene rings. By means of these conclusions a stability sequence for the isomers of multi layered [2.2]metacyclophanes can be deduced. In connection with this study a synthesis of triple layered [2.2]metacyclophanes is offered, which opens the door to substituted derivatives.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00906887
