Silylium-Catalyzed Carbon–Carbon Coupling of Alkynylsilanes with (2-Bromo-1-methoxyethyl)arenes: Alternative Approaches

Article abstract of DOI:10.1002/ejoc.201800777

The catalytic activation of alkynylsilanes towards 2-halo-1-alkoxyalkyl arenes gives β-halo-substituted alkynes. It involves the chemoselective substitution of an alkoxide by an alkyne in the presence of a neighboring C(sp³)–Br bond in a cationic C–C bond-forming event. Two complementary protocols to accomplish this new transformation are reported. The outcome of a direct approach based on mixing the precursors with a freshly prepared solution of the active catalytic species (TMSNTf₂) is compared with an alternative based on smooth release of the required silylium ions upon selective activation of the alkyne by gold(I) (JohnPhosAuNTf₂). The two approaches gave satisfactory results to access this otherwise elusive alkynylation process, which furnishes 4-bromo-substituted alkynes and tolerates various functional groups.