Encapsulated Cobalt–Porphyrin as a Catalyst for Size‐Selective Radical‐type Cyclopropanation Reactions

A cobalt–porphyrin catalyst encapsulated in a cubic M 8 L 6 cage allows cyclopropanation reactions in aqueous media. The caged‐catalyst shows enhanced activities in acetone/water as compared to pure acetone. Interestingly, the M 8 L 6 encapsulated catalyst reveals size‐selectivity. Smaller substrates more easily penetrate through the pores of the “molecular ship‐in‐a‐bottle catalysts” and are hence converted faster than bigger substrates. In addition, N ‐tosylhydrazone sodium salts are easy to handle reagents for cyclopropanation reactions under these conditions.