Ring-expansion protocol: preparation of synthetically versatile dihydrotropones

A condition for exclusive Z-control in the oxidative ring-opening reaction of 3-cyclohexene-1,2-diols via use of NaI[O.sub.4] without any acid treatment is demonstrated. The process complemented the ring-contraction protocol from 3-cyclohexene-1,2-diols via the E-controlled oxidative ring-opening reaction followed by the intramolecular Baylis-Hillman reaction to produce cyclopentenols.