Difluoromethylenation of Alkynes: Streamlined Access to Allyl Difluorides.

A direct difluoromethylenation of alkynes has been developed using HF/pyridine as a dual acidic and fluorinating medium. The reaction proceeds via in situ generation of a primary oxocarbenium ion from formaldehyde, enabling efficient formation of two C(sp3)─F bonds and one C(sp2)═C(sp2) bond in a single step without the need for pre-functionalized reagents. This strategy offers a concise route to allyl difluorides as a complementary approach to incorporate difluoromethylene motifs into complex molecular frameworks. Additional spectroscopic and computational investigations provide insights into this mechanism.