Palladium-catalyzed 1,1-alkynylbromination of alkenes with alkynyl bromides.

The palladium-catalyzed 1,1-alkynylbromination of terminal alkenes with a silyl-protected alkynyl bromide is reported. The method tolerates a diverse range of alkenes including vinylarenes, acrylates, and even electronically unbiased alkene derivatives to afford propargylic bromides regioselectively. Mechanistic studies and DFT calculations indicate that the 1,1-alkynylbromination reaction proceeds the migration of the Pd center followed by the formation of a π-allenyl Pd intermediate, leading to the stereoselective reductive elimination of the C(sp)-Br bond at the propargylic positon.