Easy Access to Modified Cyclodextrins by an Intramolecular Radical Approach

A simple method to modify the primary face of cyclodextrins (CDs) is described. The 6I‐O‐yl radical of α‐, β‐, and γ‐CDs regioselectively s the H5II, located in the adjacent D‐glucose unit, by an intramolecular 1,8‐hydrogen‐atom‐transfer reaction through a geometrically restricted nine‐membered transition state to give a stable 1,3,5‐trioxocane ring. The reaction has been extended to the 1,4‐diols of α‐ and β‐CD to give the corresponding bis(trioxocane)s. The C2‐symmetric bis(trioxocane) corresponding to the α‐CD is a stable crystalline solid whose structure was confirmed by X‐ray diffraction analysis. The calculated geometric parameters confirm that the primary face is severely distorted toward a narrower elliptical shape for this rim. The successful match of cyclodextrins (CDs) with radical chemistry is reported. The di‐alkoxyl radical generated from 6I,IV‐diol‐α‐CD under oxidative conditions led to a stable crystalline bis(1,3,5‐trioxocane) with a guest n‐hexane molecule. The primary face of the bis(1,3,5‐trioxocane) is severely distorted toward a narrower elliptical shape.