Metal-free C(sp3)-H functionalization of sulfonamides via strain-release rearrangement

With the increasing awareness of sustainable chemistry principles, the development of an efficient and mild strategy for C(sp(3))-H bond activation of nitrogen-containing compounds without the utilization of any oxidant and metal is still highly desired and challenging. Herein, we present a metal-free reaction system that enables C-H bond functionalization of aliphatic sulfonamides using DABCO as a promoter under mild conditions, affording a series of alpha,beta-unsaturated imines in good yields with high selectivities. This protocol tolerates a broad range of functionalities and can serve as a powerful synthetic tool for the late-stage modification of complex compounds. More importantly, control experiments and detailed DFT calculations suggest that this process involves [2 + 2] cyclization/ring-cleavage reorganization, which opens up a new platform for the establishment of other related reorganization reactions.

Automated summary

This study presents a metal-free reaction system for C-H bond functionalization of aliphatic sulfonamides under mild conditions, offering a series of alpha,beta-unsaturated imines in good yields with high selectivities. Control experiments and detailed DFT calculations suggest a [2 + 2] cyclization/ring-cleavage reorganization process, opening up new possibilities for other related reorganization reactions.