Bicyclanes IV. Preparation and properties of the methyl‐cis‐bicyclo[3.3.0]octanes

Abstract

KONINK LIJKE/SHELL-LABOR ATOR UM, AMSTERDAMThe syntheses of the five methyl-cis-bicyclo[3.3.0]octanes are described. The exo-3 compound could only be obtained as a mixture with an equal amount of its endo-3 isomer. IntroductionIn the course of our investigation into the isomerization of perhydroindane 1 we required authentic samples of the five methyl-cis-bicyclo[3.3.0]-octanes for identification purposes.A literature search revealed that none of the isomers, I-, endo-Z, exo-2-, endo-3-, and exo-3-methyl-cis-bicyclo[3.3.0]octane had been described before. Mair et a1.2 have demonstrated the presence of only one of them in petroleum, but could not establish its spatial configuration.

Composition of the branched paraffin-cycloparaffin portion of petroleum, 140.degree. to 180.degree.C

“…l-Methyl-cis-bicyclo[3.3.0]octane was tentatively identified from its proton resonance spectra which showed the presence of a bridgehead methyl group and by comparing its C13 NMR spectrum with that of a number of model bicycloparaffins (7). The identity was confirmed by comparison of its infrared spectrum with that reported by Knotnerus and Schilling (6). exo-2-Methyl-cis-bicyclo[3.3.0]octane and endo-2-methyl-cts-bicyclo[3.3.0]octane were identified by direct comparison of their infrared and NMR spectra with those of the synthetic compounds, exo-3-Methyl-ci's-bicyclo[3.3.0]octane was isolated from fractions boiling near 153.7°C.…”

“…The five methyl-ct's-bicyclo[3.3.0]octanes have been synthesized recently by Knotnerus and Schilling (6). They give infrared spectra for the 1-, exo-2-, endo-2-, and endo-3-methyl isomers and for a mixture containing 40% of the exo-3-and 60% of the endo-3-methyl isomers.…”