Synthesis of β-cyclodextrin derivatives functionalized with azobenzene

Two approaches for the synthesis of β-cyclodextrin and bis(β-cyclodextrin) bearing azobenzene on the primary face are reported. First, the nucleophilic substitution of mono-6-tosyl-β-cyclodextrin by azobenzene anion derivatives was reinvestigated and found to produce mono-3,6-anhydro-β-cyclodextrin as a side product. A slight modification of the reported reaction conditions including the use of Cs2CO3 led to a substantial improvement of the yields. In addition, a convenient method based on the application of click chemistry led to 1,2,3-triazole-linked azobenzene-cyclodextrin derivatives in good yields.