Ga(III)-catalyzed cycloisomerization approach to (+/-)-icetexone and (+/-)-epi-icetexone.

A Ga(III)-catalyzed cycloisomerization reaction provides expedient access to a benzannulated cycloheptadiene bearing a cyano group, which has been applied to the syntheses of several icetexane diterpenoids including icetexone and epi-icetexone. Key to the synthesis is a novel in situ generated diazene rearrangement.