The rearrangements of allylic hydroperoxides derived from (+)-valencene

Abstract

(+)-Valencene (I) reacts with triplet oxygen to give 84% of the secondary β-hydroperoxide (II) and 15% of the α-hydroperoxide (III); reaction with singlet oxygen gives principally (ca. 80%) the tertiary β-hydroperoxide (IV). This undergoes a Schenck rearrangement to give suprafacially the β [graphic omitted] hydroperoxide (II) by a non-dissociative mechanism which does not involve exchange of oxygen in an atmosphere of ¹⁸O₂. The hydroperoxide (II) then undergoes a slower Smith epimerization to the α-hydroperoxide (III) by a dissociative mechanism which involves substantial (>55%) exchange.