ACID-CATALYZED ISOMERIZATION OF TRICYCLICS

The isomerization of 1,2,3,4,5,6,7,8-octahydroanthracene (OHA) and 1,2,3,4,5,6,7,8-octahydrophenanthrene (OHP) was carried out at 0, 30, and 50° with an HF-BF3 catalyst system. At 0 and 30°, with an excess of anhydrous hydrofluoric acid and a boron trifluoride to substrate mole ratio of 0.6 and 0.7 to 1, equilibrium was reached when ~70% of the OHP was isomerized to OHA. The OHA:OHP ratio in the hydrocarbon and acid layers was also established under conditions that provided information regarding the position of the thermodynamic equilibrium of the hydrocarbons and carbonium ions involved. Isomerization with less than equivalent amounts of HF and BF3 was shown to have a pronounced effect on the OHA: OHP ratio. A comparison of the HF- and HF-BF3-catalyzed isomerization of OHP was made. Competition experiments have shown the following relative order of basicity: OHA > OHP ≃ prehnitene > durene. © 1968, American Chemical Society. All rights reserved.