Directional degradation of lignin model compounds by a palladiumcatalyzed alkynylation under ambient environment

Abstract

A palladium-catalyzed regioselective cascade alkynylation of diaryl ethers in basic ionic liquid C(sp2)-O bond cleavage for the assembly of structurally diverse aryl internal alkynes is described. In the presence of 1 mol% of IPrtBu-Pd-Cin-Cl as the catalyst, ionic liquid [Apmim]BF4 as the solvent and the base, a wide variety of terminal alkynes and diaryl ethers could be excellently tolerated. This alkynylation protocol features good yields (up to 94 %), excellent functional group compatibility (40 examples) and green synthetic process. Notably, the robustness and potential of this approach have also been successfully certified by the valorization of polyphenylene oxide wastes, gram scale experiment, recycling experiment (6 times), and late-stage modification of pharmaceuticals.