Efficient synthesis of E-alpha-haloenones through chemoselective alkyne activation over allene with triazole-Au catalysts.

The E-alpha-haloenones were prepared through a triazole-Au complex (TriA-Au) catalyzed propargyl acetate rearrangement and sequential allene halogenation. The reactions proceeded with only 1% catalyst loading, giving the challenging kinetic products in excellent yields and good to excellent stereoselectivity. These results not only provided the first example for the synthesis of challenging kinetic E-haloenones, but also revealed triazole-Au complexes as effective catalysts in promoting chemoselective activation of alkynes over allenes.