Supramolecular complexation and photocyclodimerization of methyl 3-methoxy-2-naphthoate with modified γ-cyclodextrins

Abstract

A series of modified γ-cyclodextrins (CDs) were prepared as chiral host for catalyzing the enantiodifferentiating photocyclodimerization of methyl 3-methoxy-2-naphthoate (NA). The complexation behavior of NA with modified γ-CDs was studied by UV–vis, fluorescence, and circular dichroism spectroscopies. All of the modified γ-CDs formed stable 1:2 host–guest complex with NA, and binding affinities for two-step complexation critically depended on the structure of modified γ-CDs. The enantioselectivity of NA photocyclodimerization was also significantly affected by the modification of γ-CD. The secondary rim-modification considerably reduced the enantioselectivity, for which the interrupted hydrogen-bonding network, leading to a flexible CD skeleton, is most probably responsible.