Water-soluble octa acid capsule as a reaction container: Templated photodimerization of indene in water

•Selective photodimerization of indene in the aqueous medium was achieved by encapsulation of indene within a self-assembled cavitand capsule.•The major product (photodimer) formed within capsular complex is uncommon in organic solvents by both direct excitation and sensitization approaches.

In the context of green chemistry, identifying strategies to carry out organic reactions in aqueous medium in the absence of organic and inorganic reagents is important. We show below that octa acid (OA), a water-soluble cavitand, is capable of solubilizing water insoluble reactant in water and yielding selective product by confining the reactants and intermediates during a light initiated reaction. By employing indene as the substrate we have observed that the OA capsule upon irradiation facilitates the formation of anti-head–tail dimer, the isomer that is generally not obtained upon direct excitation and triplet and electron transfer sensitizations in isotropic organic solvents.

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