Stereochemistry of some tricyclo[5.4.0.0]undecane and related isopropyldecalin derivatives

Abstract

Compounds previously formulated as derivatives of tricyclo[5.4.0.03,5]undecane (i), with a trans-configuration at the junction of the two six-membered rings, are now shown to have the cis-configuration, on the basis of chemical and spectroscopic evidence (n.m.r., c.d., and i.r.). Cleavage of the cyclopropyl ring of the tricycloundecane system leads to isopropyl-cis-decalin derivatives, although these may subsequently undergo isomerisation to isopropyl-trans-decalin derivatives, given a suitable reaction path. One series of isopropyl-cis-decalins (26) is shown to have undergone a novel inversion of the configuration of the isopropyl group during the cyclopropyl-opening process. The configurations and preferred conformations of most of the compounds in this series are dominated by non-bonded interactions, which strongly destabilize the trans-tricycloundecane skeleton, and particular conformers of some of the cis-decalin derivatives.