Highly Regioselective and Diastereoselective Photooxygenation of (alpha)-Cyclogeranyl Derivatives

Methylene blue-sensitized photooxygenation of several (alpha)-cyclogeranyl derivatives affords the exocyclic allylic hydroperoxides in 94-99% regioselectivity, while the diastereoselectivity varies from 50-97% de in favor of the cis isomer, depending on the substituents. By contrast, the ene reaction with N-phenyltriazolinedione affords significantly different regioselectivity and diastereoselectivity.