Host-guest interaction-induced selective oxidation of a substrate inside an aqueous Pd₆L₄ cage

Chemical transformations inside artificial hosts like cages have been a booming field of research. However, the use of such artificial hosts for carrying out the selective transformation of one molecule from a mixture of different molecules has been underexplored. Herein, we report the oxidation of the benzylic C(sp³)-H of alkylarenes inside an aqueous Pd₆L₄ cage 1 without using any traditional oxidant. 1 was an efficient host in inducing complete oxidation of alkyl arenes such as xanthene, thioxanthene, fluorene, and acridine derivatives inside its cavity, which other reported analogous Pd₆ cages did not show under similar conditions. It was also observed that encapsulation within the cage was a necessary criterion for oxidation to occur in water. Using this criterion and the higher binding affinity of cage 1 to fluorene over other fluorene derivatives such as 2-bromofluorene and 2,7-dibromofluorene, 1 was able to selectively oxidize fluorene from a mixture of fluorene derivatives through selective encapsulation. This work provides insight into an alternative approach for the selective oxidation of active methylene-containing organic compounds using differences in host-guest affinity in an aqueous environment.