Optimisation of the reaction conditions was performed with hetero-stilbene 1a using a Vapourtec UV-150 photochemical reactor and a 150 W (365 nm) UV lamp (Table ). For this substrate, we found the ideal conditions to use the stilbene (2 mM) together with iodine (1.1 equiv.) and THF (20 equiv.) in Toluene with a flow rate of 6 ml/min (residence time 100 s) at 55 °C, affording thieno [4]helicene substrate 2a in an excellent 94% yield (Table and Table ).