pH-Controlled Supramolecular Enantiodifferentiating Photocyclodimerization of 2-Anthracenecarboxylate with Capped ?-Cyclodextrins

Abstract

γ-Cyclodextrins capped with p-cresolbisbenzimidazole at the primary rim were synthesized and used as chiral hosts for mediating the enantiodifferentiating [4 + 4] photocyclodimerization of 2-anthracenecarboxylate. The use of 6A,6E-capped γ-cyclodextrin led to the formation of the anti-head-to-head photodimer in –5% enantiomeric excesses (ee) at pH 11 but in 28% ee at pH 6 with accompanying switching of product chirality, for which a pH-responsive conformational change of the capping moiety is likely to be responsible.