Preparation and characterization of nano-CaO based on eggshell waste: Novel and green catalytic approach to highly efficient synthesis of pyrano[4,3-b]pyrans

A general and efficient catalytic system for Pd/C-catalyzed ligand-free aerobic Suzuki cross-coupling reactions was developed. The reaction tolerated a wide range of aryl bromides with a hydrophilic group or a hydrophobic group without any additives in water. Moreover, the catalytic system was successfully extended to the cross-couplings of heteroaryl halides with various arylboronic acids. The Pd/C catalyst could be reuse three times without significant loss of catalytic activity.

Graphical AbstractA highly efficient and recyclable catalytic system for the Pd/C-catalyzed, ligand-free Suzuki reaction was developed; a wide range of aryl bromides were tolerated, and the reaction proceeded without any additives in water.Figure optionsDownload as PowerPoint slide