Metal‐Free Multifunctionalization of Alkynes Promoted by Acid and Selectfluor

ABSTRACT

Herein, we describe a metal‐free approach for the tetrafunctionalization of internal alkynes using an acid/Selectfluor system. This method efficiently forms four new chemical bonds (C─F, C─C, and C─N) in a single step, enabling the construction of amide‐containing fluorene under mild conditions. The reaction proceeds through a carbocation‐based mechanism initiated by 1,6‐enyne cyclization, with acetonitrile serving as both solvent and the amide source. Gram‐scale synthesis demonstrates the practical utility of this transformation, while mechanistic studies verify the origin of the amide group and the involvement of a deuterium kinetic isotope effect (DKIE). This work establishes a distinct, transition‐metal‐free pathway for alkyne multifunctionalization, offering a complementary strategy to existing synthetic methods.