Gold-catalysed transformations in water

Seheme 16.29 Water-soluble gold complexes employed in alkyne hydration. 

Another attractive green alternative is the use of ionic liquids (IL) as solvents/ IL present several advantages over conventional solvents. The final product of the reaction can he typically separated hy simple extraction with an organic solvent and the IL phase might he reused in catalysis. IL have heen found to he adequate solvents to conduct several gold-catalysed transformations. 

Krause also explored the cycloisomerisation of a-hydroxyallenes in ionic liquids. The reaction proceecled smoothly in that medium and the catalyst 

The selected examples discussed above show that gold catalysis can be conducted in solvent-free conditions, water or ionic liquids. Although the vast majority of gold-catalysed protocols make use of conventional solvents, these examples should encourage researchers in the search for more sustainable protocols to explore gold-promoted reactions in neat or non-conventional solvents. 

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