β‐Cleavage of Potassium Bicyclo[2.2.2]oct‐5‐en‐2‐olates. Stereoselective synthesis of (±)‐trichodiene

The transformations of 12 bicyclo[2.2.2]oct‐5‐en‐2‐ols (V or VI) to 3‐(cyclohex‐3‐enyl)‐2‐alkanones (III or IV), via β‐cleavage of their potassium alkoxides in HMPA, has been investigated (cf. Table 1). As an illustration of this synthetic methodology, a stereoselective synthesis of (±)‐trichodiene ((±)‐1) is described which involves the β‐cleavage of the tricyclic potassium alkoxides 46a and 47a to cyclopentanone 4 (cf. Scheme 7).