A Site-Selective C(sp³)-H Chlorination Boosted by an Imidazolium-Functionalized Cage in Water

Abstract

The utilization of a confined cavity in a coordination cage to manipulate the reaction pathways can nicely complement the synthetic shortage of site-selective reactions. However, harmonization of the transition state in the cavity is a significant challenge. To address this issue, we have designed an imidazolium-functionalized cage with a regular octahedral geometry composed of 12 imidazolium linkers and 6 Cu4-calix[4]arene nodes. As a catalyst, the diisopropylphenylimidazolium functionality enables an efficient N-chlorination, and the created cavity favors a six-membered cyclic transition state for chlorine atom transfer, boosting the site-selective C(sp3)–H chlorination of amides/sulfonamides in the water. Our mechanistic investigations have disclosed the rate-determining N–Cl activation mode within the cavity for the chlorine atom transfer pathways.