Photoinduced Transition-Metal-Free Alkynylation of Alkyl Pinacol Boronates

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 togeneratephotoactivetetra-coordinatedboron species. Various functional groupswerewell 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.

Automated summary

An unprecedented visible-light-induced transition-metal-free alkynylation of alkyl pinacol boronates was demonstrated using alkynyl phenylsulfones as alkynylation reagents and 4CzIPN as the organic photocatalyst. Common Lewis bases like sodium methoxide or sodium hydroxide were used to generate photoactive tetra-coordinated boron species. The selective monoalkynylation of diboronates was achieved, preserving one boron group in the product for potential further transformations, as confirmed by radical trapping experiments and EPR analysis.