AuI‐Catalyzed Haloalkynylation of Alkenes

The formal insertion of alkenes into aromatic chloro‐ and bromoalkynes takes place under cationic gold catalysis. This haloalkynylation reaction can be performed with cyclic, gem‐disubstituted and monosubstituted alkenes, using BINAP, triazolo[4,3‐b]isoquinolin‐3‐ylidene ligands or SPhos, respectively. The products were isolated in moderate to excellent yields and with complete diastereo‐ and regioselectivity; the halogen atom bonding the more substituted carbon of the alkene. Preliminary experiments showed that the enantioselective haloalkynylation of cyclopentene can be performed with (S)‐BINAP to afford the insertion products with moderate to good enantioselectivities. Formally inserted: Cyclic and terminal alkenes react with bromo‐ and chloroalkynes under cationic gold catalysis to afford haloalkynylation products. Appropriate choice of ligands and conditions enabled the obtention of valuable haloalkynes with high levels of diastereo‐ regio‐ and enantioselectivity (see scheme).