Trifluoromethylation/Cyclization of Alkenes with Trifluoromethylsulfonyl‐Pyridinium Salt for the Synthesis of CF3‐Substituted Fused Indoles under Photocatalyst Free Conditions

A photochemical trifluoromethylation/cyclization of alkenes to access trifluoromethyl‐substituted fused indoles using trifluoromethylsulfonyl‐pyridinium salt (TFSP) is achieved under photocatalyst‐free conditions. Mechanistic studies revealed the formation of an electron donor–acceptor complex between indole and TFSP, distinguishing this protocol from iridium‐catalyzed TFSP‐based trifluoromethylation reactions and suggesting a different mechanistic pathway.