Mild diazenylation of Csp2-H and Csp3-H bonds via arylazo sulfones

We report an unprecedented transition-metal-free method to access diverse non-symmetric azo derivatives via cross-couplings of arylazo sulfones with C-sp2-H and C-sp3-H bonds. Instead of serving as aryl radical precursors, arylazo sulfones demonstrate the unexplored potential of being stable electrophilic diazo sources that easily undergo arylation and alkylation under basic conditions, and enhance the atom utilization efficiency. Compared with the low-stability diazonium salts, the relatively stable arylazo sulfones also offer the advantage of being suitable for large-scale storage. This strategy exhibits merits such as simple operation, mild conditions, transition-metal-free process, broad substrate scopes, and good air compatibility. Mechanistic studies on the functionalization of arylazo sulfones reveal that a substitution mechanism is favored over diaziridine rearrangement. The Ms-substituted N atom, which is relatively weakly electrophilic, uncommonly accepts the nucleophilic attack. The results presented herein shed light on the unconventional utilization of arylazo sulfones, opening up novel avenues for the functionalization of organic frameworks.