Preparation and molecular structure determination of a 1,2,3, 4-tetracyclohexylcyclohexane existing in a twist-boat conformation

Hydrogenation of 1,2,3,4-tetraphenylbenzene using a Pd/C catalyst results in the formation of two stereoisomeric 1,2,3,4-tetracyclohexylcyclohexane products. Fractional crystallization enables the separation of the two stereoisomers. X-ray studies of the major product reveal it to be the cis-trans-cis isomer, while the minor product has a cis-team-trans configuration. X-ray data reveal the existence of a central ring in the minor compound in a twist-boat conformation. These data indicate that four neighboring isopropyl groups are enough to make the twist-boat as the lowest energy conformation of a cyclohexyl ring.