Intermolecular Addition of 1,3‐Diketones to Terminal Alkynes Catalyzed by Gold/Copper Cooperative System

ABSTRACT An intermolecular addition of 1,3‐diketones to terminal alkynes catalyzed by a gold/copper cooperative system is described herein. While conventional gold catalyst systems bearing simple phosphine ligands such as PPh 3 show little or no activity for this transformation, the combination of a phosphine–gold complex with Cu(NTf 2 ) 2 enables an efficient C─C bond formation. The reaction efficiency strongly depends on the kind of counteranion of copper salt, the weakly coordinating NTf 2 − anion playing a crucial role. Under the optimized conditions, a variety of 1,3‐diketones undergo addition to terminal aryl alkynes to afford the corresponding alkenylated products in moderate to high yields. A range of arylacetylenes bearing either electron‐donating or electron‐withdrawing substituents can be employed well, but aliphatic and internal alkynes are unreactive. We believe that the plausible reaction pathway includes both the activation of alkyne by a π‐acidic gold species and the facilitation of an enolate formation from 1,3‐diketone by a copper salt. This study demonstrates a simple and effective gold/copper catalytic system for intermolecular addition without using specially designed biarylphosphine ligands.