Metal-Free Activation of a C(sp)-H Bond of Aryl Acetylenes.

C(sp)-H Bond activation of acetylene molecule still remains a challenge for synthetic organic chemists. In practice, acetylenes are activated by strong bases and metals. The first example for activating acetylenic protons under base and metal-free conditions is reported here. It involves a general method for synthesizing propargylic derivatives of cotarnine. An array of tetrahydroisoquinolines alkaloids was synthesized by C(sp)-H bond activation of aromatic acetylenes with cotarnine at room temperature. A DFT-based mechanism is proposed for the reaction.