Additive‐free and Diastereoselective Synthesis for trans‐Disubstituted‐2,3‐dihydro‐benzofurans via [4 + 1] Annulation between p‐QMs and TFISYs

An additive‐free and diastereoselective [4 + 1] annulation between ortho‐hydroxyphenyl‐substituted para‐quinone methides and CF3‐substituted imidoyl sulfoxonium ylides is developed, providing a facile and practical route to diverse trans‐2,3‐dihydrobenzofurans with high efficiency. This protocol features mild conditions, broad substrate scope and easy to operate.