Enantiodifferentiating photoisomerization of cyclooctene included and sensitized by benzoate modified β-cyclodextrin derivatives: switching of product chirality by solvent

Solvent effect upon asymmetric photosensitization has been investigated in the enantiodifferentiating photoisomerization of cyclooctene(1Z), sensitized by benzoate modified β-cyclodextrin derivatives bearing nitrogen, oxygen or sulfur substituents. The enantiomeric excess (ee) and E/Z ratio of reaction products were susceptible to the concentration of methanol in the aqueous solution, which could switch to the chirality of product unprecedentedly. Further investigation indicated that the conformation of the modified CDs in aqueous methanol solutions with 1Z were highly sensitive to both the substituent(s) on benzoate moiety of the modified CDs and the concentration of methanol. Solvent content represents a new versatile tool to efficiently manipulate the asymmetric photochemical reactions, in which the chirality of products can be switched by simply changing the methanol content of reaction solvent rather than synthesizing the antipodal sensitizers.