Copper-free Sonogashira cross coupling in ionic liquids

In the present Letter the use of ionic liquids based on butylpyridinium salts (C4PyPF6, C4PyBF4, and C4PyNO3) is described in the Sonogashira reaction. Aiming the development of recyclable catalytic system using Pd(II) salts as precursors, the importance of the induction period prior to the addition of substrates was established. A new methodology that can be performed under Cu(I)-free and at mild conditions was established. Good conversions were obtained and good recyclability was observed.