Phenols Add To Alkynes Via Cooperative Gold

A new reaction uses cooperative gold catalysts to achieve an organic synthetic goal infrequently explored: adding tertiary alcohols and phenols to alkynes. Steven P. Nolan of the University of St. Andrews, in Scotland, and colleagues had previously developed a dinuclear gold hydroxide catalyst, [Au(NHC)]₂(μ-OH)][BF₄], where NHC is an N-heterocyclic carbene. They reasoned that this compound could behave as two catalysts and applied it to the hydrophenoxylation of alkynes. They predicted that the BF₄ segment would react with an alkyne to form a gold-alkyne complex and that the OH segment would react with phenols to form a gold-phenoxide complex. The researchers tested this idea with numerous alkynes and phenols and found that the dinuclear gold catalyst indeed behaved like two cooperative gold catalysts (Angew. Chem. Int. Ed. 2013, DOI: 10.1002/anie.201304182). The reactions produced various aryl vinyl ethers with moderate to good yields, the authors say. They add that “these findings provide new insights into the chemistry of gold catalysis and open the door to the development of new catalytic transformations.”