Synthesis of 3‑Alkyl- or 3‑Allenyl-2-amidobenzofurans via Electrophilic Cyclization of <i>o</i>‑Anisole-Substituted Ynamides with Carbocations

A facile carbocation-induced electrophilic cyclization reaction has been developed for the synthesis of 3-alkyl- or 3-allenyl-2-amidobenzofurans from o-anisole-substituted ynamides and diarylmethanol or 1,1-diarylprop-2-yn-1-ol