Photoinduced transition-metal-free alkynylation of alkyl pinacol boronates

Abstract

An unprecedented visible-light-induced transition-metal-free alkynylation of alkyl pinacol boronates has been demonstrated with alkynyl phenylsulfones as the alkynylation reagents and 4CzIPN as the organic photocatalyst. Common sodium methoxide (NaOMe) or sodium hydroxide (NaOH) was used as the Lewis base to generate photoactive tetra-coordinated boron species. Various functional groups were well tolerated. The selective monoalkynylation of diboronates was achieved to keep one boryl group in the product for potential further transformations. Radical trapping experiments and electron paramagnetic resonance (EPR) analysis confirmed the generation of alkyl radical intermediate.