Palladium(II)-Catalyzed Homocoupling of Oxazole/Thiazole in Absence of Silver Oxidant
Homocoupling of oxazole/thiazole via palladium-catalyzed C-H bond activation using oxone as an oxidant has been achieved in moderate to excellent yields with good functional group tolerance. No other additive or ligand was employed in this efficient reaction. Comparing to our previously reported homocoupling of oxazole/thiazole, the absence of stoichiometric silver oxidant renders this reaction more environment-benign and cost-effective. A preliminary mechanism involving a Pd Ⅱ /Pd Ⅳ catalytic cycle is also proposed. Further exploration of this environmental-benign oxidant on other categories of coupling reactions, as well as applications of this revised homocoupling to structural modification of oxazole/thiazole-containing natural products, are undergoing in our lab.