AlCl₃‑Catalyzed Annulations of Ynamides Involving a Torquoselective Process for the Simultaneous Control of Central and Axial Chirality

A highly torquoselective process for simultaneous control of central and axial chirality by the annulation of terminally substituted ynamides with <i>o</i>-quinone methides is reported. In the presence of AlCl₃, a sequence comprising a [2 + 2] cycloaddition followed by the torquoselective 4π-electrocyclic ring opening and 6π-electrocyclic ring closure leads to highly stereoselective formation of diastereoisomeric 4-amino-2<i>H</i>-chromenes. Terminally unsubstituted ynamides undergo AlCl₃-catalyzed [4 + 2] cycloaddition with <i>o</i>-quinone methides providing 2-amino-4<i>H</i>-chromenes.