Scheme 1.

Synthesis of [4]helicene precursors and structures of the catalysts tested. Reagents and conditions: a) Pd₂(dba)₃ (5 mol %), SPhos (10 mol %), Cs₂CO₃ (4 equiv), THF/H₂O (10:1), 80 °C, 24 h, 3 a, 62 %; 3 b, 67 %; 3 c, 65 %; 3 d, 89 %; b) 19 (9 mol %), AgSbF₆ (9 mol %), DCM, 7 a, 87 %; 7 b, 42 %, both from 6 (two steps); c) Tf₂O (1.5 equiv), pyridine (4.0 equiv), and then 5 a or 5 c, Pd₂(dba)₃ (5 mol %), SPhos (10 mol %), Cs₂CO₃ (2 equiv), THF/H₂O (10:1), 80 °C, 24 h, 8 a, 60 %; 8 b, 25 % (two steps). X‐ray structure of 2 g, H atoms, co‐crystallized solvents and SbF₆ anions are removed for clarity. Arene moieties are drawn as reduced sticks, ellipsoids drawn at 50 % probability level.16