An all-suprafacial [3,3] sigmatropic rearrangement could in principle take place through either a chair-like or a boat-like transition state:

(a) According to the following results, which of these two transition states is preferred?

(b) When the terpene germacrone is distilled under reduced pressure at 165°C, it is transformed to b-elemenone by a Cope rearrangement. Deduce the structure of germacrone, including its stereochemistry.

Transcribed Image Text:

chair-like transition state boat-like transition state