Visible-Light-Promoted Catalytic Redox-Neutral Alkynylation of Alkyl Boronic Acids/Boronates

We present a catalytic, redox-neutral strategy for producing internal alkynes through the cross-coupling of alkyl boronic acids and boronates with (hetero)aryl acetylenic bromides. This method proceeds under mild conditions, requires no metal catalysts, and accommodates a wide variety of substrates including medicinally relevant molecules. Mechanistic investigations indicate the in situ formation of a boronate anion complex along with the generation of an alkyl radical under the reaction conditions.