Synthesis and Reactivity of Six-Membered Cyclic Diaryl λ³-Bromanes and λ³-Chloranes

Despite the remarkable advancements in hypervalent iodine chemistry, exploration of bromine and chlorine analogues remains in its infancy due to their difficult synthesis. Herein, we introduce six-membered cyclic λ³-bromanes and λ³-chloranes. Through single-crystal X-ray structural analyses and conformational studies, we delineate the crucial bonding patterns pivotal for the thermodynamic stability of these compounds. Notably, these investigations reveal pronounced π-π stacking phenomena within the crystal lattice of hypercoordinated bromine(III) and chlorine(III) species. Their reactivity profile is explored as they are radical precursors or electrophilic reagents in metal-free intermolecular biaryl couplings, O- and S-arylations, and Cu(I)-promoted intramolecular biaryl couplings which is complementary to the known reactivity of five-membered bromanes and chloranes. Mechanistic insights are provided, elucidating the pathways governing their reactivity and underscoring the potential in organic synthesis.