Reinventing the Corey-Fuchs Reaction under Ball Milling Conditions: A Mechanochemical Pathway to Bromoalkynes.

The classical Corey-Fuchs reaction, a two-step transformation of aldehydes into alkyne derivatives, is successfully adapted to mechanochemical conditions. The solvent-free process involves two sequential ball-milling steps: (1) the formation of gem-dibromoalkenes from aldehydes using only half the conventional amount of triphenylphosphine, followed by (2) a base-promoted dehydrohalogenation that unexpectedly affords bromoalkynes instead of terminal alkynes. Although developing a one-pot protocol proved unfeasible, the stepwise approach provides excellent conversions, short reaction times, and significantly improved sustainability metrics (PMI, E-factor). The study shows that substrate electronics and milling parameters govern reaction efficiency and selectivity, expanding the mechanochemical toolbox for greener, phosphorus-mediated synthesis.