AbstractWe have studied the enantioselective transannular aminohalogenation reaction of unsaturated medium‐sized cyclic benzosulfonamides by using both chiral Brønsted acid and phase‐transfer catalysis. Under optimized conditions, a variety of bicyclic adducts can be obtained with good yields and high enantioselectivities. The mechanism of the reaction was also studied by using computational tools; we observed that the reaction involves the participation of a conformer of the nine‐membered cyclic substrate with planar chirality in which the stereochemical outcome is controlled by the relative reactivity of the two pseudorotational enantiomers when interacting with the chiral catalyst.