Die Ableitung der Stereochemie von 1‐Isopropyl‐4‐methyl‐bicyclo[3.1.0]hexan (cis‐und trans‐Thujan) durch Protonenresonanz‐Spektroskopie

Abstract

Isomeren. Thujan R ist 97,6% optisch reines Isomeres mit 2,4O/, Thujan A, wahrend letzteres noch 11% Thujan R enthalten soll. Die von chemischen Argumenten unabhangige Kestinimung der relativen Konfigurationen und eine Studie der Konformationen dieser beiden Kohlenwasserstoffe durch 100-MHz-ProtonenresonanzSpektroskopie ist Gegenstand der nachfolgenden Arbeit. Orientierende Messungen der Protonenspektren bei 60 MHz sind bereits in der vorgenannten Arbeit ausgewertet worden.

Chemistry of thujane derivatives

“…A unique correlation between the nmr spectra in a variety of aprotic solvents and the relative configurations which have been assigned on nmr and chemical evidence can be made for the thujones and their derived alcohols and amines only if the preferred conformation of the ring is in most cases boatlike.12,16,17 The ORD spectra of certain ketones derived from umbellulone were also consistent with this interpretation,21 and the nmr spectrum of frani-thujane reveals a preferred boat shape, although that of the cis isomer is consistent with a half-chair with a flattened C6 ring. 22 The situation can be rationalized by considering the thujane skeleton as a flexible system which adopts the conformation best to minimize interactions between groups at C(3) or C(5) and the methylene bridge of the cyclopropane ring, which is usually the boat form, though in some cases a half-chair or chair may be better; cf.…”