Studies in sesquiterpenes—LV: Isolongifolene(part 6): Mechanism of rearrangement of longifolene to isolongifolene-I

The gross mechanism of rearrangement of longifolene to isolongifolene has been elucidated by using site-specifically labelled longifolene-4, 4, 5, 5-d₄ and shown to follow the pathway proposed by Berson et al., which involves an exo, exo Me shift, in preference to the endo, endo Me migration route proposed earlier. An efficient synthesis of longifolene-4, 4, 5, 5-d₄, the key compound in the present investigation, is described.