Selective synthesis of 4,5-dihydropyrenes by a Brønsted acid-catalyzed cyclization cascade of biphenyl-embedded enynes

A metal-free Brønsted acid-catalyzed cascade cyclization enables the selective synthesis of 4,5-dihydropyrenes from biphenyl-embedded trienynes. Proceeding under mild conditions with a low <i>E</i>-factor and broad substrate scope, it provides a sustainable approach to access these scarcely explored scaffolds.