ELECTROCHEMICAL REACTIONS .21. STEREOCHEMISTRY OF THE HYDRODIMERS FROM CYCLOHEXENONE, ISOPHORONE, AND (+/-)-PIPERITONE

The photodimerisation of cyclohexanone, isophorone, and piperitone leads to tricyclic diketones of established stereochemistry. Birch reduction of the head-to-head photodimers causes cleavage of the cyclobutane bond α to two carbonyl groups followed by reduction of the carbonyl functions. Oxidation of each alcohol so formed affords one of the two isomeric diketonic hydrodimers obtained by either electrochemical or dissolving metal reduction of the initial cyclohexenone. These reactions establish the stereochemistry of the diketonic hydrodimers of cyclohexenone, isophorone, and (±)-piperitone.