Recyclable Hybrid Silica-Based Catalysts Derived from Pd-NHC Complexes for Suzuki, Heck and Sonogashira Reactions

Two silylated PdNHC complexes were immobilized on hybrid silicas by sol-gel cocondensation with tetraethyl orthosilicate (TEOS) and performed well as recyclable catalysts towards the Heck, Suzuki, and Sonogashira coupling reactions. Remarkable conversion and recyclability were achieved in the Suzuki reaction with a challenging aryl chloride. No side products and no undesired homocoupling were observed in Suzuki or Heck reactions, which facilitates the final purification step for the cross-coupling products. High turnover numbers and turnover frequencies were found for copper- and phosphane-free Sonogashira reaction between p-bromoacetophenone and phenylacetylene.