Gold Meets Selenium: Dual Activation of Selenium‐Containing Propargyl Alcohols Towards the Synthesis of 2H‐Chromenes and Mechanistic Insights

Herein, we report the synthesis of seleno‐substituted chromenes from selenoalkynes and phenols. In this cascade reaction, the applied gold catalyst not only functions as a π‐acid, but also as a Lewis acid, enabling the propargylic substitution in the first step to connect the oxygen carbon bond. Under the optimal reaction condition a total of 26 chromenes were accessible by this modular access. During scale up experiments, the hydrolysis of the vinylselenium substructure to the corresponding chromenones was observed. By revisiting the electron‐rich starting materials, four chromenones were produced following a one‐pot reaction using a single gold catalyst. To better understand the interaction of gold and selenium, a series of nuclear magnetic resonance studies and high‐resolution mass spectrometry studies were performed, which led to the proposal of a mechanism for this transformation.