We developed a novel method for synthesizing 2‐(4‐hydroxyaryl)‐3,4‐fused tricyclic
dihydrobenzopyrans with 2,3‐syn and 3,4‐syn motif based on the acid‐promoted cascade cyclization via vinylidene para‐quinone methide intermediates. Using easily prepared linear substrates, TFA‐promoted
cascade cyclization proceeded in the presence of triethylsilane, affording a series
of five to seven‐membered ring‐fused dihydrobenzopyran derivatives in moderate to
excellent yield in a highly diastereoselective manner. The developed method provided
new access to potent and selective ERβ agonists.