Masahiro Anada

The first continuous‐flow intramolecular dehydrative Friedel–Crafts alkylation of 1‐substituted ω‐arylalkan‐1‐ols is successfully achieved. The reaction is completed by a single pass of a solution of substrates in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) at 25 °C through a cartridge packed with hydroxy‐substituted sulfonic acid‐functionalized silica gel (HO‐SAS) as a water‐tolerant immobilized Brønsted acid catalyst with a residence time of only 40–80 s. The efficiency of the concise catalytic process is demonstrated by the short‐step synthesis of the bisnorlignan natural product pachypostaudin A.