pH-controlled supramolecular enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate with capped gamma-cyclodextrins

摘要

gamma-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 6(A), 6(E)-capped gamma-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.