Design and Synthesis of Bis-thioureas Ligands for Pd-Catalyzed Heck Reaction

摘要

The palladium-catalyzed arylation of olefins (the Heck reaction) is one of the most versatile tools for C-C bond formation in organic synthesis. Phosphine ligands are generally used to stabilize the reactive palladium intermediates, the air-sensitivity of phosphine ligands, however,places significant limits on their synthetic applications. Recently, Yang1 and we2 have reported Heck and Suzuki reactions of highly active arenediazonium salts and halides catalyzed by air-stable monothiourea-Pd complexes.In this presentation, we disclose our results on the design and synthesis of novel bis-thiourea ligands. We report that the bis-thiourea-Pd(0) complexes are highly air-, moisture- and thermally stable catalysts for Heck reactions of aryl halides. We tested the catalytic activity of their complexes with Pd (0) in the Heck reaction between iodobenzene and n-butyl acrylate. Our work shows that in NMP at 180℃, quantitative yield was achieved within 0.5h when 0.001mol% Pd was used (TOF up to 200,000). Furthermore, solvent-free condition can be applied in our catalytic system and very high TON (up to 1,000,000) is obtained within 12h.Further investigations aimed at clarification of the reaction scope are currently in progress.